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ICOM 2008 Oral Presentation Proceedings Sheraton Waikiki Hotel Honolulu, Hawaii, USA http://www.icom2008.org Hosted by : Membrane Technology and Research, Inc. The University of Texas at Austin The University of California, Los Angeles Meeting Chair: Ingo Pinnau Membrane Technology and Research, Inc. 1360 Willow Road, Suite 103 Menlo Park, CA 94025 Tel: (650) 328-2228 x 113 Fax: (650) 328-6580 E-mail: [email protected] Meeting Co-Chair: Benny Freeman Dept. of Chemical Eng. University of Texas at Austin 10100 Burnet Road, Building 133 Austin, TX 78758 Tel: (512) 232-2803 Fax: (512) 232-2807 E-Mail: [email protected] Meeting Co-Chair: Yoram Cohen Dept. of Chemical & Biomolecular Eng. University of California, Los Angeles BOX 951592, 5531 BH Los Angeles, CA 90095-1592 Tel: (310) 825-8766 Fax: (310) 206-4107 E-Mail: [email protected] International Congress on Membranes and Membrane Processes Honolulu, Hawaii July 12-18, 2008

Oral Proceedings

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Page 1: Oral Proceedings

ICOM 2008 Oral Presentation Proceedings Sheraton Waikiki Hotel Honolulu, Hawaii, USA

http://www.icom2008.org

Hosted by:

Membrane Technology and Research, Inc.

The University of Texas at Austin

The University of California, Los Angeles

Meeting Chair: Ingo Pinnau Membrane Technology and Research, Inc. 1360 Willow Road, Suite 103 Menlo Park, CA 94025 Tel: (650) 328-2228 x 113 Fax: (650) 328-6580 E-mail: [email protected]

Meeting Co-Chair: Benny Freeman Dept. of Chemical Eng. University of Texas at Austin 10100 Burnet Road, Building 133 Austin, TX 78758 Tel: (512) 232-2803 Fax: (512) 232-2807 E-Mail: [email protected]

Meeting Co-Chair: Yoram Cohen Dept. of Chemical & Biomolecular Eng. University of California, Los Angeles BOX 951592, 5531 BH Los Angeles, CA 90095-1592 Tel: (310) 825-8766 Fax: (310) 206-4107 E-Mail: [email protected]

International Congress on Membranes and

Membrane Processes Honolulu, Hawaii July 12-18, 2008

Page 2: Oral Proceedings

The organizers of ICOM 2008 gratefully

acknowledge the generous sponsorship of the

meeting by the following organizations:

Page 3: Oral Proceedings

Organizing Committee:

Professor Yoram Cohen University of California,

Los Angeles

Sponsorship Committee Chair

Professor John Pellegrino University of

Colorado at Boulder

Student Award Manager, Poster

Session

Professor Douglas Gin University of

Colorado at Boulder Food Coordinator

Professor Albert Kim University of Hawaii

Onsite Logistics Manager/Sponsorship

Committee, Poster Session

Professor Glenn Lipscomb University of Toledo Website Manager

Dr. Ed Sanders Air Liquide Workshop Coordinator

Dr. Richard Ubersax Onsite Logistics and Technical Support,

Poster Session

Page 4: Oral Proceedings

ICOM International Advisory Board:

Pierre Aimar.................................................France Paul Armistead................................................ USA Richard Baker ................................................. USA Georges Belfort ............................................... USA Neal Chung............................................. Singapore Wookjin Chung.............................................. Korea Enrico Drioli ....................................................Italy Eric Favre ....................................................France Francesc Giralt .............................................. Spain Michael Guiver ............................................Canada Akon Higuchi............................................... Taiwan Anita Hill ..................................................Australia Yong Soo Kang.............................................. Korea Albert Kim ...................................................... USA Sung Soo Kim ............................................... Korea Hidetoshi Kita ............................................... Japan Bill Koros........................................................ USA Young Moo Lee.............................................. Korea TorOve Leiknes ...........................................Norway Jerry Lin......................................................... USA Glenn Lipscomb............................................... USA Andrew Livingston ............................................. UK Jim McGrath ................................................... USA Kazukiyu Nagai ............................................. Japan Richard Noble ................................................. USA Yoram Oren .................................................. Israel Don Paul ........................................................ USA Klaus-Viktor Peinemann............................. Germany Peter Pintauro ................................................. USA Giulio Sarti .....................................................Italy Raphael Semiat ............................................. Israel Kamalesh Sirkar .............................................. USA Tae Moon Tak ............................................... Korea Richard Ubersax .............................................. USA Tadashi Uragami ........................................... Japan Matthias Wessling........................... The Netherlands Yuri Yampolskii............................................. Russia Andrew Zydney ............................................... USA

Page 5: Oral Proceedings

ICOM 2008 Staff:

The University of Texas at Austin Student Administrative Staff

Mr. Brandon Rowe Ms. Elizabeth Van Wagner Mr. Geoff Geise Mr. Victor Kusuma

The University of Texas at Austin

Student Staff

Ms. Katrina Czenkusch Mr. Tom Murphy Ms. Lauren Greenlee Mr. Grant Offord

Mr. Hao Ju Dr. Claudio Ribeiro Mr. James Kyzar Ms. Alyson Sagle

Mr. Hua (Richard) Li Mr. Kevin Tung Mr. Bryan McCloskey Ms. Yuan-Hsuan Wu

Mr. Dan Miller Mr. Wei Xie

The University of Texas at Austin

Administrative Assistant

Ms. Kumi Smedley

The University California, Los Angeles

Student Staff

Mr. Alex Bartman Mr. Eric Lyster

Centennial Conferences

Annett D’Antonio

Sheraton Hotel Staff:

Mr. Robert Morishige .....................Convention & catering service manager Mrs. Julene Davis..........................Sales manager Mr. Jeff Gionet..............................Director of telecommunications Mrs. Shirley Yamamoto..................Director of convention services

Page 6: Oral Proceedings

Sheraton Waikiki Map:

Page 7: Oral Proceedings

ICOM 2008 Workshop Schedule:

Saturday, July 12 -Workshop: Membrane-Based Gas Separations (O’ahu) .................... 8:00am -Professor Benny Freeman, University of Texas at Austin -Professor Glenn Lipscomb, University of Toledo -Dr. Hans Wijmans, Membrane Technology Research, Inc.

-Workshop: Fuel Cells (Honolulu) ..................................................... 8:00am -Professor Peter Pintauro, Case Western Reserve -Professor Ryszard Wycisk, Case Western Reserve

-Workshop: Polymeric and Inorganic Membrane Materials and Membrane Formation (Wailua) ........................... 8:00am -Professor Jerry Y. S. Lin, Arizona State University -Dr. Michael D. Guiver, National Research Council of Canada, Ottawa

-Workshop: Measurement Methods for Membranes (Kahuku).................................................................. 8:00am -Professor John Pellegrino, University of Colorado at Boulder Sunday, July 13 -Workshop: Emerging Membrane Materials and Manufacturing Methods (Wai’anae)..................... 8:00am -Dr. Klaus V. Peinemann, GMT Membrantechnik GmbH -Dr. Suzanna P. Nunes, GKSS, Germany -Professor Bruce Hinds, University of Kentucky

-Workshop: Membrane Desalination Technology (Kohala/Kona).......................................................... 8:00am -Dr. Craig Bartels, Hydranautics -Dr. Rich Franks, Hydranautics

ICOM 2008 Social and Business Schedule:

Sunday, July 13 -Opening Reception (Ocean Terrace/Pool Area) .......................6:30pm – 9:30pm Monday, July 14 -Elsevier Reception (Ballroom Foyer).......................................5:30pm – 6:30pm -Poster Session I (Lana’i Ballroom)..........................................6:30pm – 9:30pm Tuesday, July 15 -NAMS Business Meeting (Wai’anae) .......................................5:30pm – 6:30pm -Poster Session II (Lana’i Ballroom) ........................................6:30pm – 9:30pm Wednesday, July 16 -ICOM Banquet (Hawai’i Ballroom) ........................................ 6:00pm – 10:00pm Thursday, July 17 -Poster Session III (Lana’i Ballroom) .......................................6:30pm – 9:30pm

Page 8: Oral Proceedings

Monday, July 14 – Morning Sessions

8:00AM Plenary I (Hawai’i Ballroom): Professor James E. McGrath (Virginia Tech, Blacksburg, Virginia, USA)

Fuel Cell Polymer Electrolyte (PEM) Derived from Disulfonated Random and Block Poly(arylene ether) Copolymer System 9:00AM Coffee Break (Ballroom Foyer)

Gas Separation I (Kaua’i)

Chair: Don Paul, The University of Texas at Austin, USA Co-Chair: Giulio Sarti, Universita Degli Studi Di Bologna, Italy

Drinking and Wastewater

Applications I (Maui)

Chair: Dibakar Bhattacharyya, University of Kentucky, USA Co-Chair: Maria Norberta de Pinho, Instituto Superior Tecnico, Portugal

Polymeric Membranes I(Moloka’i)

Chair: Klaus-Viktor Peinemann, GKSS, Germany Co-Chair: Chris Cornelius, Sandia National Laboratories, USA

Biomedical and Biotechnology I

(Honolulu/Kahuku)

Chair: Robert van Reis, Genentech, Inc., USA Co-Chair:Andrew Zydney, The Pennsylvania State University, USA

Membrane Fouling – General Topics

(O’ahu)

Chair: Robert H. Davis, University of Colorado, USA Co-Chair: Isabel Escobar, University of Toledo, USA

Membrane Modeling I – Fundamental

Approaches (Waialua)

Chair: Albert Kim, University of Hawaii at Manoa, USA Co-Chair: David Ford, University of Massachusetts, USA

9:30AM Beyond Inorganic-Organic Nanocomposites for Molecular Separations Wessling, University of Twente, The Netherlands

Reuse/Recycle Water Opportunities and Challenges in Food/Bio Processing Industry Using Membrane Technology: Is this Myth or Reality? Muralidhara, Cargill Inc., Savage, Minnesota, USA

Layer-by-Layer Assembly in Membrane Pores for Ion Separations and Biocatalysis Bhattacharyya, Hollman, Butterfield, Smuleac, Datta University of Kentucky, Lexington, Kentucky, USA

Fouling Characteristics of Virus Filtration Membranes Zydney, Bakhshayeshi, The Pennsylvania State University, University Park, Pennsylvania, USA Kuriyel, Jackson, PALL Life Sciences, USA Mehta, Paley, Genentech, USA

Protein Fouling of Polymeric Membranes: Modeling and Experimental Studies Using Ultrasonic Frequency-Domain Reflectometry Hernandez, Kujundzic, Cobry, Greenberg, University of Colorado at Boulder, Boulder, Colorado, USA Ho, Li, University of Cincinnati, Cincinnati, Ohio, USA

Membrane Analysis and Simulation System (MASS) Faibish, Pointer, Roux, Tentner, Argonne National Laboratory, Argonne, Illinois, USA

10:15AM Tailor Made Polymeric Membrane based on Segmented Block Copolymer for CO2 Separation Car, Stropnik, University of Maribor, Slovenia Yave, Peinemann, Institute of Polymer Research, GKSS Research Centre Geesthacht GmbH, Germany

Integrated Membrane System for Waste Water Reuse with Innovative PVDF UF Membrane and Low Fouling RO Membrane Kitade, Takagi, Kantani, Taniguch, Uemura, TORAY Industries, Inc., Otsu, Shiga, Japan

Unusual Temperature Dependence of Positron Lifetime in a Polymer of Intrinsic Microporosity Rätzke, De Miranda, Kruse, Faupel, Technische Fakultät der CAU, Kaiserstr, Germany Fritsch, Abetz, Institut für Polymerforschung, Germany Budd, Selbie, Univ. of Manchester, Manchester, United Kingdom McKeown, Ghanem, Cardiff University, Cardiff, United Kingdom

Developments in Membrane Affinity Chromatography for Monoclonal Antibody Recovery Sarti, Dimartino, Boi, University of Bologna, Bologna, Italy

Assessment of Ultrasound as Fouling Control Technique in Crossflow Microfiltration for the Treatment of Produced Water Silalahi, Leiknes, Norwegian University of Science and Technology, Norwegian

Development of Novel Molecular Modeling Technique for Membrane Fouling in Water Treatments Takaba, Suzuki, Sahnoun, Koyama, Tsuboi, Hatakeyama, Endou, Carpio, Kubo, Miyamoto, Tohoku University, Japan Kawakatsu, Nishida, Watanabe, Kurita Water Industries Ltd., Tochigi, Japan

10:45AM Segmented Block Copolymers: A Molecular Toolbox to Tailor the Mass Transport Properties of Polymeric Nanocomposites Reijerkerk, University of Twente, The Netherlands

Impact of Seasonal Water Quality Changes on Low Pressure Membrane Filtration of an Activated Sludge-Lagoon Effluent Roddick, Nguyen, Fan, Harris, RMIT University, Melbourne, Australia

Macrovoid Formation in Polymeric Membranes and Critical Factors in Fabricating Macrovoid-Free Hollow Fiber Membranes Chung, Peng, Wang, National University of Singapore, Singapore

Bioactive Membranes for Liver Tissue Engineering De Bartolo,Salerno, Piscioneri, Morelli, Rende, Campana, Drioli, Institute on Membrane Technology, National Research Council of Italy, ITM-CNR, Italy

Impact of Diluate Solution Composition in Protein and Magnesium on Membrane Fouling During Conventional ED Pourcelly, Institut Europeen des Membranes, France Casademont, University Laval, Québec, Canada Bribiesca, Farias, Bazinet, Institut Nutraceutiques et Aliments Fonctionnels, Québec, Canada

Electroosmotic Flow in a Lysozyme Crystal: Molecular Dynamics Simulation Jiang, Hu, National University of Singapore, Singapore

11:15AM Gas Separation Using Ionic Liquid Polymers Noble, Gin, Bara, Carlisle, Voss, Finotello, University of Colorado, Boulder, Colorado, USA

Investigating and Evaluating Different Concepts of Membrane-Based Technologies for a Cleaner Production in the Automotive Industry Lyko, Wintgens, Buchmann, Melin, RWTH Aachen University, Germany Herse, Ford-Werke GmbH, Germany

Preparation of Porous Poly (ether ether ketone) Membranes Ding, Bikson, PoroGen Corporation, Woburn, Massachusetts, USA

Separation and Purification of Hematopoietic Stem Cells from Human Blood through Surface-modified Membranes Higuchi, Nat. Central Univ. & Nat. Res. Institute for Child Health & Development, Tokyo, Japan Chang, Christian University, Taoyuan, Taiwan Ruaan, Chen, National Central University, Taoyuan, Taiwan

MBR Activated Sludge Filterability Alteration in Stress Circumstances Geilvoet, Graaf, NIeuwenhuijzen, Delft University of Technology, The Netherlands

Theoretical Analysis of the Theoretical Analysis of Effects of Asymmetric Membrane Structure on Fouling during Microfiltration Ho, Li, University of Cincinnati, Cincinnati, Ohio, USA Duclos-Orsello, Millipore Corp., Billerica, Massacheusetts, USA

11:45AM Development of High Temperature CO2-Selective Porous Ceramic Membranes Ku, Ramaswamy, Ruud, Willson, Narang, GE Global Research, Niskayuna, New York, USA

Membranes in Clean Technologies Koltuniewicz, University of Technology, Wroclaw, Poland Drioli, Professor in Istituto per la Tecnologia Delle Membrane, Italy

Design of New Membranes Assisted By Block Copolymer Assembly Deratani, Querelle, Quémener, Université Montpellier, France Ellouze, Ecole Nationale d'Ingénieur de Tunis, France Phan, Gigmes, Bertin, University Aix-Marseille, France

Membrane Chromatography: Protein Purification Using Newly Developed, High-Capacity Adsorptive Membranes Bhut, Husson, Clemson University, Clemson, South Carolina, USA Wickramasinghe, Colorado State University, Fort Collins, Colorado, USA

Scale-up of Lab Investigations on Fouling in MBR Potentials and Limitations Kraume, Schaller, Iversen, Drews, Technische Universität, Germany Wedi, Engineering Office ATM, Germany Torre, Berlin Centre of Competence for Water, Germany

Modeling Virus Filtration: A Population Balance Approach Abbas, Pavanasam, Chen, University of Sydney, Australia Ansumali, Nanyang Technological University, Singapore

12:15PM Solubility and Diffusivity of Organic Vapors in Mixed Matrix Membranes Formed By High Free Volume Glasses Loaded with Fumed Silica Sarti, Ferrari, De Angelis, Galizia, University of Bologna, Italy Merkel, MTR- Membrane Technology and Research, Menlo Park, California, USA

Oxygen and Carbon Dioxide Control by Membrane Contactors in Desalination Criscuoli, Carnevale, Institute on Membrane Technology, ITM-CNR, Italy Mahmoudi, ,University of Chlef, Algeria Gaeta, Lentini, Reggiani, GVS S.P.A., Italy Drioli, University of Calabria, Italy

Effect of Network Structure Modifications of Cross-linked Poly(ethylene oxide) Membranes on Gas Separation Properties Kusuma, Freeman, The University of Texas at Austin, Austin, Texas, USA Danquah, Borns, Comer, Kalika, University of Kentucky, Lexington, Kentucky, USA

Using Micro-Dialysis to Monitor Tissue Production Wu, University of Durham, Durham, United Kingdom Field, University of Oxford, Oxford, United Kingdom

Visual Characterization of Fouling Behavior By Activated Sludge Model Solutions Le-Clech, Marselina, Stuetz, Chen, University of New South Wales, Sydney, Australia

Direct Simulation of Particle Migration in Cross-Flow Microfiltration Fujita, Oda, Akamatsu, Nakao, The University of Tokyo, Tokyo, Japan

Page 9: Oral Proceedings

Monday, July 14 – Afternoon Sessions

12:45PM Lunch Break Hybrid and Novel

Processes I (Kaua’i)

Chair: Glenn Lipscomb, University of Toledo, USA Co-Chair: Hans Wijmans, Membrane Technology & Research, Inc., USA

Nanofiltration and Reverse Osmosis I -

Membranes (Maui)

Chair: Andrew Livingston, Imperial College, United Kingdom Co-Chair: Isabel Escobar, University of Toledo, USA

Nanostructured Membranes I

(Moloka’i)

Chair: Peter Budd, University of Manchester, USA Co-Chair: Detlev Fritsch, GKSS Research Centre, Germany

Fuel Cell Membranes I (Honolulu/Kahuku)

Chair: Susanna Nunes, GKSS – Forschungszentrum, Germany Co-Chair: Peter N. Pintauro, Case Western Reserve University, USA

Desalination I (O’ahu)

Chair: Raphael Semiat, Technion - Israel Institute of Technology, Israel Co-Chair: Eric Hoek, University of California at Los Angeles, USA

Composite Polymeric Membrane Formation

(Waialua)

Chair: Richard Baker, Membrane Technology & Research Inc., USA Co-Chair: Klaus-Vikton Peinemann, GKSS, Germany

2:15PM Scaleable Membrane Separations for the Lignocellulosic-to-Ethanol Biorefinery? Pellegrino, Colyar, Gutierrez-Padilla, University of Colorado at Boulder, Boulder, Colorado, USA Hettenhaus, cea Inc., Charlotte, North Carolina, USA Schell, National Renewable Energy Laboratory, Golden, Colorado, USA

Development of Reverse Osmosis FT-30 Membranes with Polyethylene Oxide Brush Modified Antifouling Surface Mickols, Niu, Thorpe, Abaye, Dow Water Solutions, Edina, Minnesota, USA

Novel Polymers of Intrinsic Microporosity (PIMs): Towards an Understanding of Structure-Property Relationships McKeown, Ghanem, Msayib, Cardiff University, Cardiff, United Kingdom Budd, Univesity of Manchester, Manchester, United Kingdom Fritsch, GKSS, Germany

Polyoxadiazole Nanocomposite Fuel Cell Membranes Operating above 100°C Nunes, Gomes, GKSS Research Centre, Germany

Energy Cost Optimization in RO Desalting and the Thermodynamic Restriction Zhu, Christofides, Cohen, University of California, Los Angeles, Los Angeles, California, USA

A New Method to Fabricate Membranes using Glassy Self Assembly Templating Ho, Feng, Co, University of Cincinnati, Cincinnati, Ohio, USA

3:00PM Reducing the Energy Demand of Bio-Ethanol Through Salt-Extractive Distillation and Electrodialysis Pfromm, Hussain, Kansas State University, Manhattan, Kansas, USA

Desalination Membranes Based on Directly Sulfonated Poly(arylene ether sulfone) Copolymers Park, University of Ulsan, Ulsan, Korea Xie, Freeman, University of Texas at Austin, Austin, Texas, USA Paul, Lee, Macromolecules and Interfaces Institute and Department of Chemistry, Blacksburg, Virginia, USA Riffle, McGrath, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA

Physical Aging and Mixed-Gas Transport Properties of Microporous Polymers for Gas Separation Applications Thomas, Pinnau, Membrane Technology and Research, Inc., Menlo Park, California, USA Guiver, Du, Song, Institute for Chemical Process and Environmental Technology, National Research Council, Ottawa, Ontario, Canada

Nanocomposite Membranes with Low Methanol Permeability for the Direct Methanol Fuel Cell Ladewig, Martin, Costa, Lu, The University of Queensland, Australia

Characterizing RO Membrane Performance when Desalinating High pH Produced Water from the Oil Extraction Process Franks, Bartels, Hydranautics, Oceanside, California, USA

Ultra-Thin Polymeric Interpenetration Network with Enhanced Separation Performance Approaching Ceramic Membranes for Biofuel Jiang, Chung, National University of Singapore, Singapore Jean, Chen, University of Missouri- Kansas City, Kansas City, Missouri, USA

3:30PM Membrane Separation Techniques in the Continuous Fermentation and Separation of Butanol Du, Beitle, Clausen, Carrier, Hestekin, University of Arkansas, Fayetteville, Arkansas, USA

Structure-Property Relationships in PEG-Based Hydrogel Membrane Coatings Sagle, Ju, Freeman, Sharma, The University of Texas at Austin, Austin, Texas, USA

Polymers of Intrinsic Microporosity: New Copolymers, Syntheses, Properties and Applications. Fritsch, Heinrich, Bengtson, Pohlmann, GKSS Research Centre, Germany

Proton Conducting Graft Copolymer Electrolyte Membranes for Fuel Cells Kim, Koh, Park, Roh, Yonsei University, Seoul, Korea

Submerged Hollow Fiber Pre-Treatment to RO in Seawater Applications Ye, Sim, Chen, Fane UNESCO Center for Membrane Science and Technology, Sydney, Australia

PTFE-Polyamide Thin-Film Composite Membranes from Interfacial Polymerization for Pervaporation Dehydration of Alcohol-Water Mixtures Jeng, National Chung Hsing University, Taichung, Taiwan Yu, Liu, Lai, Chung Yuan University, Chung-Li, Taoyuan, Taiwan

4:00PM Power Generation by Reverse Electrodialysis Dlugolecki, Nymeijer, Metz, Wessling, University of Twente, The Netherlands

Engineering Molecular Weight Cut-Off of Organic Solvent Nanofiltration (OSN) Membranes for Natural Product Fractionation Sereewatthanawut, Lim, Boam, Membrane Extraction Technology Ltd, London, United Kingdom See Toh, Livinston, Imperial College, London, United Kingdom

Characterizing the Pore Size Distribution in Nanostructured Membranes Hill, CSIRO, Australia

Nanocomposite Proton Exchange Membranes for Hydrogen Fuel Cells: Self-Humidification, Molecular Nucleation and Dynamic Simulation Zhang, Gao, Hong Kong University of Science and Technology, Hong Kong, China

RO Membrane Desalting in a Feed Flow Reversal Mode Uchymiak, Alex, Christofides, Cohen, University of California, Los Angels, Los Angeles, California, USA Daltrophe, Weissman, Gilron, Ben-Gurion University, Beer Sheva, Israel Rallo, Universitat Rovira i Virgili, Tarragona, Catalunya, Spain

Preparation of Poly(vinyl alcohol) Composite Reverse Osmosis and Nanofiltration Membranes Ramos, Cristiano, Federal University of Rio de Janeiro, Brazil

4:30PM Reverse Electrodialysis: Energy Recovery from Controlled Mixing Salt and Fresh Water Post, Hamelers, Buisman, Wageningen University, Wetsus, The Netherlands

High-Temperature Nanofiltration Using Porous Titania Membranes Tsuru, Ogawa, Yoshioka, Hiroshima University, Higashi-Hiroshima, Japan

Polymers of Intrinsic Microporosity in the Application of Organic Solvent Nanofiltration Heinrich, Fritsch, Merten, Bengtson, Dargel, GKSS Research Centre, Germany

Sulfonated Polyimide Membranes for Polymer Electrolyte Fuel Cells Okamoto, Matsuda, Hu, Chen, Endo, Higa, Yamaguchi University, Ube, Yamaguchi, Japan

Evaluating the Performance of Single-Pass RO and Multi-Pass NF/RO Systems for Seawater Desalination Tanuwidjaja, Hoek, University of California, Los Angeles, Los Angeles, California, USA

Experimental Verification of Effect of Support on Membrane Performance Takagi, Shukugawa Gakuin College, Nishinomiya, Japan Pihlajamäki, Nyström Lappeenranta University of Technology, Lappeenranta, Finland Shintani, Nitto Denko Corporation, Osaka, Japan

5:00PM Electrocatalytic Membranes for Glucose/O2 Biofuel Cell Géraldine, Sophie, Marc, Marc, Christophe, European Membrane Institute, France

Polypyrrole Modified Solvent Resistant Nanofiltration Membranes Li, Vandezande, Vankelecom, Centre for Surface Chemistry and Catalysis, Faculty of Bioscience Engineering, Leuven, Belgium

An Efficient Method for Preparing High Molecular Weight Polymers of Intrinsic Microporosity (PIM)s with Cyclic-Free Structure via Fast Polycondensation Du, Robertson, Song,Guiver, Institute for Chemical Process and Environmental Technology, National Research Council, Ottawa, Ontario, Canada Thomas, Pinnau, Membrane Technology and Research, Menlo Park, California, USA

Syntheses and Physical Properties of Novel Polymer Electrolyte Membranes Comprising Poly(diphenylacetylene)s Ito, Yamamoto, Akiyama, Takeda, Yokota, EBARA Research Co. Ltd., Kanagawa, Japan Nagase, School of Engineering, Tokai University, Kanagawa, Japan

Performance Testing of a Large Seawater RO Desalination Plant Khawaji, Royal Commission for Jubail & Yanbu, Yanbu Al-Sinaiyah, Saudi Arabia Wie, Saudi Arabian Parsons Limited, Yanbu Al-Sinaiyah, Saudi Arabia

Study on Improvement of Composite Reverse Osmosis Membranes Gao, Zhou, Yu, Wu, The Development Center of Water Treatment Technology, Hanzhou, China An, College of Materials Science and Chemistry, Zhejiang University, Hangzhou, China

Page 10: Oral Proceedings

Tuesday, July 15 – Morning Sessions

NAMS Alan S. Michaels Award

(Kaua’i)

Chair: Greg Fleming, Air Liquide, USA Co-Chair: Rich Ubersax, Air Liquide, USA

Nanofiltration and Reverse Osmosis II – Imaging and

Characterization (Maui)

Chair: Ho Bum Park, University of Ulsan, Korea Co-Chair: Andrew Livingston, Imperial College, United Kingdom

Nanostructured Membranes II

(Moloka’i)

Chair: Bruce Hinds, University of Kentucky, USA Co-Chair: Anita Hill, CSIRO, Australia

Pervaporation and Vapor Permeation I (Honolulu/Kahuku)

Chair: Leland Vane, US EPA, USA Co-Chair: Ivy Huang, Membrane Technology and Research, Inc., USA

Osmotically Driven Membrane Processes

(O’ahu/Waialua)

Chair: Jeff McCutcheon, Stony Brook Water Purification Co., USA Co-Chair: Klaus-Viktor Peinemann, GKSS, Germany

Asymmetric Polymeric Membrane Formation

(Wai’anae)

Chair: Max Ekiner, Air Liquide, USA Co-Chair: Christiano Borges, Universidade Federal de Rio de Janeiro, Brazil

8:15AM Some Reflections and Projections Based on Thirty Five Years in Membranes Koros, Georgia institute of Technology, Atlanta, Georgia, USA

8:50 – 9:15AM

A Versatile Membrane System for Bulk Storage and Shipping of Produce in a Modified Atmosphere Paul, Kirkland, University of Texas at Austin, Austin, Texas, USA Clarke, Landec Corporation, Menlo Park, California, USA

8:15AM On the Correlation Between MWCO Values for Nanofiltration Membranes and Quantitative Porosity Analysis Using Variable Energy Positron Beams De Baerdemaeker, Ghent University, Gent, Belgium Boussu, Bruggen, KU Leuven, Leuven, Belgium Weber, Lynn, Washington State University, Pullman Washington, USA

Nanofiltration of Electrolyte Solutions by Sub-2nm Carbon Nanotube Membranes Fornasiero, Park, Holt, Stadermann, Noy, Bakajin, Lawrence Livermore National Laboratory, Livermmore, California, USA Kim, University of California at Davis, Davis, California, USA In, Grigoropoulos, University of California at Berkeley, Berkeley, California, USA

Bioethanol Production Using Pervaporation and Vapor Permeation Membranes Huang, Baker, Membrane Technology & Research, Menlo Park, California, USA Vane, The U.S. EPA, Cincinnati Laboratory, Cincinnati, Ohio, USA

Characterization of Solute Transport in Osmotically Driven Membrane Processes Hancock, Cath, Colorado School of Mines, Golden, Colorado, USA

Manipulation of Block Copolymer Nanostructure in Membranes Prepared by Solvent Evaporation and Non-Solvent Induced Phase Separation Yave, Boschetti-de-Fierro, Garamus, Peinemann, Abetz, Simon, Institute of Polymer Research, GKSS Research Centre, Germany

9:00AM Coffee Break (Ballroom Foyer) 9:30AM Enhancing Natural Gas Purification

with Advanced Polymer/Molecular Sieve Composites Miller, Vu, Chevron Energy Technology Company, Richmond, California, USA

9:30AM Positron Annihilation Spectroscopy (PAS): A New Powerful Technique to Study Membrane Structure Cano-Odena, Vandezande, Hendrix, Zaman, Vankelecom, Katholieke Universiteit Leuven, Leuven, Belgium Mostafa, Baerdemaeker, NUMAT (Nuclear Methods in Materials Science), Gent, Belgium

Aligned Carbon Nanotube Membranes: Transport Enhancement and Gatekeeper Activity Hinds, Wu, Kiess, Majumder, University of Kentucky, Lexington, Kentucky, USA

Dewatering Ethanol with Chemically and Thermally Resistant Perfluoropolymer Membranes Majumdar, Stookey, Nemser, Compact Membrane Systems, Inc., Newport, Delaware, USA

Forward-Osmosis Using Ethanol for Concentrate Minimization Pellegrino, Mendoza, University of Colorado at Boulder, Golden, Colorado, USA McCormick, Denver Water Department, Denver, Colorado, USA

Synthesis and Characterization of Nanoporous Polycaprolactone Membranes for Controlled Drug Release Yen, Lee, Ho, Ohio State University, Columbus, Ohio, USA He, Nanoscale Science and Engineering Center for Affordable Nanoengineering, Columbus, Ohio, USA

9:55AM High Performance Ultrafiltration: What Can We Learn from the Gas Separations Experts? Zydney, The Pennsylvania State University, University Park, Pennsylvania, USA

10:00AM Characterization of Biofouling Development of Spiral Wound Membrane Systems: The First NMR Study Vrouwenvelder, Loosdrecht, Wetsus, Delft University of Technology, The Netherlands Schulenburg, Johns, University of Cambridge, Cambridge, United Kingdom Kruithof, Wetsus, The Netherlands

Hybrid Biomimetic Membranes: Past, Present and Beyond Barboiu, Institut Europeen des Membranes, France

Modelling and Process Integration of Membranes for Ethanol Dehydration Friedl, Schausberger, Bosch, Vienna University of Technology, Vienna, Austria Boontawan, Suranare University of Technology, Institute of Agricultural Technology, Sc, Nakhon Ratchasima, Thailand

A Novel Hybrid Forward Osmosis Process for Drinking Water Augmentation Using Impaired Water and Saline Water Sources Lundin, Cath, Drewes, Colorado School of Mines, Golden, Colorado, USA

Catalytic PVDF Microcapsules for Application in Fine Chemistry Figoli, ITM-CNR c/o UNICAL, Italy Buonomenna, ITM-CNR c/o University of Calabria, Italy Spezzano, Drioli, ITM-CNR, Italy

10:20AM

Membranes and Reactors and Integration, Oh My! Rezac, Kansas State University, Manhattan, Kansas, USA

10:45AM Membranes for Energy Efficiency and Sustainability Murphy, Air Products, St. Louis, Missouri, USA

10:30AM Probing Polyamide RO Membrane Surface Charge, Energy, and Potential With Advanced Contact Angle Titrations Hurwitz, Hoek, University of California, Los Angeles, Los Angeles, California, USA

Nanostructured Polymers with Uniform d1 nm Pores Based on Cross-linked Lyotropic Liquid Crystals for Molecular Size-Selective Separations Gin, Zhou, Lu, Hatakeyama, Noble, University of Colorado at Boulder, Boulder, Colorado, USA Elliott, TDA Research, Inc., Wheat Ridge, Colorado, USA

Performance of a New Hybrid Membrane in High Temperature Pervaporation Van Veen, Kreiter, Engelen, Rietkerk, Vente, Energy Research Centre of the Netherlands, The Netherlands Castricum, Elshof, Univ. of Twente, The Netherlands

Osmotic Membrane Bioreactor and Pressure Retarded Osmotic Membrane Bioreactor for Wastewater Treatment and Water Desalination Achilli, Marchand, Childress, University of Nevada, Reno, Reno, Nevada, USA Cath, Colorado School of Mines, Golden, Colorado, USA

The Impact of Solvent on the Microstructure of Integrally Skinned Polyimide Nanofiltration Membranes before and after Casting Patterson, Costello, Havill, Turner, The University of Auckland, Auckland, New Zealand See-Toh, Livingston, Imperial College, London, United Kingdom

11:10AM On the Time Scales of Sorption Induced Plasticization Wessling, University of Twente, The Netherlands

11:00AM Removal of Emerging Organic Contaminants by High-Pressure Membranes: Mechanisms, Monitoring, and Modeling Drewes, Sonnenberg, Colorado School of Mines, Golden, Colorado, USA Bellona, Carollo Engineers, Broomfield, Colorado, USA

Track-Etched Polymer Membranes as Tool to Investigate Grafted Stimuli-Responsive and Other Functional Polymers for Smart Nano- and Micro-Systems Ulbricht, Friebe, Tomicki, Unv. Duisburg-Essen, Germany

Investigation of the Fundamental Differences Between Polyamide-Imide (PAI) and Polyetherimide (PEI) Membranes for Isopropanol Dehydration via Pervaporation Wang, Jiang, Chung, Goh, Nat. Univ. of Singapore, Singapore Matsuura, University of Ottawa, Ottawa, Ontario, Canada

Osmotic Power - A New, Renewable Energy Source Skilhagen, Dugstad, Statkraft AS, Norway Holt, SINTEF, Scandinavia

Nanofiltration Membranes for Polar Aprotic Solvents Lim, Sereewatthanawut, Boam, Membrane Extraction Technology Ltd., London, United Kingdom See-Toh, Livinston, Imperial College London, London, UK

11:35AM Recent Developments in Membranes for Gas Separation Applications Pinnau, Membrane Technology and Research, Inc., Menlo Park, California, USA

11:30AM Evidence of Change in the Top Surface Layer Structure of Nanofiltration Membranes due to Operating Temperature Variation Andre, Université Montpellier, France, Nihel, Saidani, Ecole Nationale des Ingénieurs de Tunis, France John, Université Paul Sabatier, France

Fixed-Charge Group-Like Behavior of the Captured Ion by Crown Ether and Its Effect on the Response of a Molecular Recognition Ion Gating Membrane Ito, Yamaguchi, Chemical Resources Laboratory, Tokyo Inst. of Tech., Yokohama, Japan

Preparation of Asymmetric Polyetherimide Membranes for Molecular Liquid Separations Favre, El-Gendi, Roizard, LSGC-CNRS, Nancy Université, France

Influence of Membrane Support Layer Hydrophobicity on Water Flux in Osmotically Driven Membrane Processes McCutcheon, Stony Brook Water Purification Co., East Setauket, New York, USA Elimelech, Yale University, New Haven, Connecticut, USA

Phase Separation Microfabrication Bikel, Lammertink, Wessling, University of Twente, The Netherlands

12:00PM Various Poly(dimethylsiloxane) Membranes for Removal of Volatile Organic Compounds from Water Uragami, Ohshima, Miyata, Kansai University, Suita, Osaka, Japan

12:00PM Characterization of the Polyamide Active Layer in NF/RO Membranes Using Gold Nanoparticles Pacheco, Reinhard, Leckie, Stanford University, Stanford, California, USA

Multifunctional Ultrathin TiO2 Nanowire Ultrafiltration Membrane for Water Treatment Du, Zhang, Pan, Sun, Nanyang Technological University, Singapore Leckie, Stanford University, Stanford, California, USA

Preparation of a Novel Styrene-Butadiene-Styrene Block Copolymer (SBS) Asymmetric Membrane for VOC Removal by Pervaporation Figoil, Drioli, Institute on Membrane Technology (ITM-CNR), Italy Sikdar, Burckle, US EPA, Cincinnati, Ohio, USA

Developing Permeation Enhanced Nanofiltration Hollow Fiber Membranes Used in Forward Osmosis Wang, Yang, Chung, National University of Singapore, Singapore Gin, Centre for Advanced Water Technology, Singapore

In-Line and In-Situ Determination of Non-Solvent, Solvent and Polymer Composition within a Film-Forming System prior to Phase Separation during VIPS Bouyer, Werapun, Pochat-Bohatier, Dupuy, Université Montpellier, Montpellier, France Deratani, CNRS, Montpellier, France

Page 11: Oral Proceedings

Tuesday, July 15 – Afternoon Sessions

12:30PM Lunch Break Gas Separations II

(Kaua’i)

Chair: Yuri Yampolski, Topchiev Institute of Petrochemical Synthesis, Russia Co-Chair: Kazu Nagai, Meiji University, Japan

Drinking and Wastewater

Applications II (Maui)

Chair: Chuyang Tang, Nanyang Technological University, China Co-Chair: Dibakar Bhattacharyya, University of Kentucky, USA

Inorganic Membranes I (Moloka’i)

Chair: Richard Noble, University of Colorado, USA Co-Chair: Hidetoshi Kita, Yamaguchi University, Japan

Membrane Fouling – UF & Water Treatment

(Honolulu/Kahuku)

Chair: Vicki Chen, UNESCO, University of New South Wales, Australia Co-Chair: Robert H. Davis, University of Colorado, USA

Membrane Modeling II – Gas Separation (O’ahu/Wailua)

Chair: Albert Kim, University of Hawaii at Manoa, USA Co-Chair: Giulio Sarti, Universita Degli Studi Di Bologna, Italy

Membrane and Surface Modification I

(Wai’anae)

Chair: Young Moo Lee, Hanyang University, China Co-Chair: Mathias Ulbricht, University of Duisburg-Essen, Germany

2:15PM Highly Gas-Permeable Substituted Polyacetylenes: Recent Advances Masuda, Kyoto University, Kyoto, Japan

Analysis of RO Membrane Performance for Municipal Wastewater Treatment Bartels, Franks, Gourley, Hydranautics, Oceanside, California, USA

Inorganic Membranes also Swell Falconer, Yu, Lee, Funke, Noble, University of Colorado, Boulder, Colorado, USA

Fouling Mechanisms and Fouling Control By Membrane Surface Modification in Ultrafiltration of Aqueous Solutions Containing Polymeric Natural Organic Matter Ulbricht, Peeva, Sustano, Universität Duisburg-Essen, Germany

Modeling Approaches for the Design of High Performance Polymer Glassy Membranes for Small Gas Molecule Separations Pullumbi, Air Liquide, Juoy-en-Josas, France Tocci, ITM-CNR, Rende (CS), Italy Heuchel, Pelzer, GKSS, Teltow, Germany

New Chemically Modified Membranes in Bioseparations Melzner, Faber, Satorius Biotech, Goettingen, Germany

3:00PM Modelling Molecular-Scale Gas Separation Thornton, Hill, CSIRO, Clayton, Australia Hilder, Hill, University of Wollongong, Wollongong, Australia

Adsorption Behavior of Perfluorinated Compounds on Thin-Film Composite Membranes Kwon, Leckie, Stanford University, Palo Alto, California, USA Shih, University of Hong Kong, Hong Kong, China Tang, Nanyang Technological University, Singapore

Synthesis and Characterization of SAPO-34 Zeolite Crystals and Membranes Employing Crystal Growth Inhibitors Carreon Venna, University of Louisville, Louisville, Kentucky, USA

A Mechanistic Study on the Coupled Organic and Colloidal Fouling of Nanofiltration Membranes Harris, Li, Rice University, Houston, Texas, USA Kim, University of Hawaii at Monoa, Honolulu, Hawaii, USA

Molecular Modeling of Free Volume in Poly (pyrrolone-imide) Copolymers Wang, University of California, Berkeley, Berkeley, California, USA Sanchez, Freeman, University of Texas at Austin, Austin, Texas, USA

Surface-Initiated Atom Transfer Radical Polymerization: A New Tool to Produce High-Capacity Adsorptive Membranes Bhut, Husson,Clemson University, Clemson, South Carolina, USA Wickramasinghe, Colorado State University, Fort Collins, Colorado, USA

3:30PM Physical Aging in Thin Glassy Polymer Films: A Variable Energy Positron Annihilation Lifetime Spectroscopy Study Rowe, Freeman, Paul, University of Texas at Austin, Austin, Texas, USA Hill, Pas, CSIRO, Clayton, Australia Suzuki, AIST, Ibaraki, Japan

RO Reject Recovery - A Challenge Towards Sustainable Water Reclamation Viswanath, Tao, Kekre, CAWT, Singapore Utilities International Pte Ltd, Singapore Ng, Lee, National University of Singapore, Singapore Seah, Public Utilities Board Board of Singapore, Singapore

Effects of Electroless Plating Conditions on the Synthesis of Pd-Ag Hydrogen Selective Membranes Bhandari, Ma, Worcester Polytechnic Institute, Worchester, Massachusetts, USA

Effect of Crossflow on the Fouling Rate of Spiral Wound Elements Eriksson, GE W&PT, Vista, California, USA

Development of a Microscopic Free Volume Theory for Molecular Self-Diffusivity Prediction in Polymeric Systems Ohashi, University of Tokyo, Tokyo, Japan Ito, Yamaguchi, Tokyo Institute of Technology, Tokyo, Japan

Gas and Liquid Permeation Studies on Modified Interfacial Composite Reverse Osmosis and Nanofiltration Membranes Louie, Reinhard, Stanford University, Palo Alto, California, USA Pinnau, Membrane Technology and Research, Menlo Park, California, USA

4:00PM Gas Permeation Parameters and Other Physicochemical Properties of a Polymer With Intrinsic Microporosity (PIM-1) Budd, University of Manchester, United Kingdom McKeown, Ghanem, Msayib, Cardiff University, United Kingdom Fritsch, GKSS, Germany Starannikova, Belov, Sanofirova, Yampolskii, Institute of Petrochemical Synthesis, Russia Shantarovich, Institute of Chemical Physics, Russia

Effects of Organic Fouling on the Removal of Trace Chemicals in Nanofiltration Membrane Processes Le-Clech Foo, Mcdonald, Khan, University of New South Wales, Sydney, Australia Drewes, Colorado School of Mines, Colorado, USA Nghiem, University of Wollongong, Wollongong, Australia

Upgrading of a Syngas Mixture for Pure Hydrogen Production in a Pd-Ag Membrane Reactor Barbieri, Brunetti, Institute for Membrane Technology, Rende (CS), Italy Drioli, University of Calabria, Rende (CS), Italy

Exploiting Local Fouling Phenomena in Dead-End Hollow Fiber Filtration: The Partial Backwash Concept van de Ven, Zwinnenburg, Kemperman, Wessling, University of Twente, The Netherlands

A Molecular Pore Network Model for Nanoporous Materials Rajabbeigi, Elyassi, Tsotsis, Sahimi, University of Southern California, California, USA

Study of a Hydrophilic-Enhanced Ultrafiltration Membrane Gullinkala, Escobar, University of Toledo, Toledo, Ohio, USA

4:30PM Addition-Type Polynorbornene with Si(CH3)3 Side Groups: Detailed Study of Gas Permeation and Thermodynamic Properties Yampolskii, Starannikova, Pilipenko, Belov, Gringolts, Finkelshtein, Institute of Petrochemical Synthesis, Russia

Emergency Water Purification Device Using Gravity Driven Membrane Filtration Jiang, Cui, University of Oxford, Oxford, United Kingdom

Preparation and Characterization of Hollow Fibre Carbon Membranes based on a Cellulosic Precursor He, Lie, Sheridan, Hagg, Norwegian University of Science and Technology, Norway

Fouling Resistant Coatings for Oil/Water Separation Wu, McCloskey, Kusuma, Ju, Freeman, The University of Texas at Austin, Austin, Texas, USA Park, University of Ulsan, Korea

Modeling and Performance Assessment of Pd- and Pd/Alloy-Based Catalytic Membrane Reactors for Hydrogen Production Ayturk, Kazantzis, Ma, Worcester Polytechnic Institute, Worchester, Massachusetts, USA

Crosslinked Poly(ethylene oxide) Fouling Resistant Coating Materials: Synthesis, Characterization, and Application Ju, McCloskey, Sagle, Freeman, University of Texas at Austin, Austin, Texas, USA

5:00PM Analysis of the Size Distribution of Local Free Volume in Hyflon® AD Perfluoropolymer Gas Separation Membranes by Photochromic Probes Jansen, Tocci, De Lorenzo, Drioli, ITM-CNR, Renda (CS), Italy Macchione, Universitia della Calábria, Rende (CS), Italy Heuchel, GKSS Research Center, Teltow, Germany

Membrane Defects and Bacterial Removal Efficiency: Effect of Alterations of the Skin and of the Macroporous Support LeBleu Causserand, Roques, Aimar, Université de Toulouse, Toulouse, France

High-Density, Vertically-Aligned Carbon Nanotube Membranes with High Flux Yu, Funke, Falconer, Noble, University of Colorado, Boulder, Colorado, USA

On the Representativeness of Model Polymers in Fouling Research Drews, TU Berlin, Berlin, Germany Shammay, Chen, Le Clech, UNESCO Centre UNSW, Sydney, Australia

Free-Volume Holes in Amorphous Polymers for Solvent Diffusion: Reconsideration of the Free-Volume Theory By Equation-of-State, Group Contribution Method, PALS Measurement and Molecular Simulation Lv, Wang, Yang, Tsinghua University, China

Dopamine: Biofouling-Inspired Anti-Fouling Coatings for Water Purification Membranes McCloskey, Freeman, The University of Texas at Austin, Austin, Texas, USA Park, University of Ulsan, Korea

Page 12: Oral Proceedings

Wednesday, July 16 – Morning Sessions

8:00AM Plenary II (Hawai’i Ballroom): Professor Young Moo Lee (Hanyang University, Seoul, Korea)

Thermally Rearranged Polymer Membranes with Cavities Tuned for Fast Transport of Small Molecules 9:00AM Coffee Break (Ballroom Foyer)

Gas Separation III (Kaua’i)

Chair: Keith Murphy, Air Products and Chemicals, USA Co-Chair: Ed Sanders, Air Liquide, USA

Drinking and Wastewater

Applications III (Maui)

Chair: Maria Norberta de Pinho, Instituto Superior Tecnico, Portugal Co-Chair: Daniel Yeh, University of South Florida, USA

Polymeric Membranes II

(Moloka’i)

Chair: Mary Rezac, Kansas State University, USA Co-Chair: Xiao-Lin Wang, Tsinghua University, China

Biomedical and Biotechnology II

(Honolulu/Kahuku)

Chair: Akon Higuchi, National Central University, Taiwan Co-Chair: Ranil Wickramasinghe, Colorado State University, USA

Membrane Modeling III – Process Simulations

(O’ahu/Waialua)

Chair: Albert Kim, University of Hawaii at Manoa, USA Co-Chair: Matthias Wessling, University of Twente, The Netherlands

Ultra- and Microfiltration I -

Transport (Wai’anae)

Chair: Tony Fane, University of New South Wales, Australia Co-Chair: Willem Kools, Millipore, Inc., USA

9:30AM Membrane Engineering Progresses and Potentialities in Gas Separations Drioli, Research Institute on Membrane Technology, ITM-CNR, Italy

Membranes and Water: the Role of Hybrid Processes Fane, Director, Singapore Membrane Technology Centre, Singapore

Optical Resolution with Chiral Polymaide Membranes Yoshikawa, Ikeuchi, Nakagawa, Kyoto Institute of Technology, Kyoto, Japan

Macroporous Membrane Adsorbers: Correlations Between Materials Structure, Separation Conditions and Performance in Bioseparations Ulbricht, Wang, Universität Duisburg-Essen, Germany Dismer, von Lieres, Hubbuch, Institut für Biotechnologie, Forschungszentrum, Jülich, Germany

Biopolymer Transport in Ultrafiltration: Role of Molecular Flexibility Zydney, Molek, Latulippe, The Pennsylvania State University, University Park, Pennsylvania, USA

Dynamic Microfiltration: Investigation of Critical Flux Measurement Methods and Improved Macromolecular Transmission Beier, Jonsson, CAPEC Technical University, Lyngby, Denmark

10:15AM Evolution of Natural Gas Treatment with Membrane Systems White, Wildemuth, W.R. Grace & Co., Littleton, Colorado, USA

Coagulation-Ceramic Microfiltration Hybrid System Effectively Removes Virus that is Difficult to Remove in Conventional Coagulation-Sedimentation-Sand Filtration Process Matsushita, Shirasaki, Matsui, Kobuke, Urasaki, Ohno, Hokkaido University, Sapporo, Japan

Dehydration of Alcohols By Pervaporation Through Polyimide Matrimid® Asymmetric Hollow Fibers with Various Modifications Jiang, Chung, Rajagopalan, National University of Singapore, Singapore

Integrated Membrane-Based Sample Prep Approach for Viral and Microbe Capture, Lysis, and Nucleic Acid Purification From Complex Samples Baggio, Souza, Murrell, Mullin, Avsola, Lindsay, Gagne, Martin, Millipore Corporation, Bedford, Massachusetts, USA

Effects of Long-Term Membrane Fouling on the Dynamic Operability of an Industrial Whey Ultrafiltration Process Yee, Wiley, UNESCO Centre for Membrane Science and Technology, Sydney, Australia Bao, School of Chem. Sciences and Eng., Sydney, Australia

An Integral Analysis of Crossflow Filtration Field, University of Oxford, Oxford, United Kingdom Wu, University of Durham, Durham, United Kingdom

10:45AM CO2 Permeation With Pebax-Based Membranes for Global Warming Reduction Nguyen, Sublet, Rouen University, France Langevin, Chappey, Valleton, CNRS, France Schaetzel, CAEN University, France

Membrane Enhanced Ultraviolet Oxidation of Polyethylene Glycol Wastewaters Patterson, Vranjes, University of Auckland, Auckland, New Zealand

New Cross-Linked Membranes For Solvent Resistant Nanofiltration Vanherck, Aldea, Vandezande, Vankelecom, Centre for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Heverlee, Belgium

Morphological and Funcational Features of Neurons Isolated from Hippocampus on Different Membrane Surfaces De Bartolo, Rende, Morelli, Salerno, Piscioneri, Gordano, Drioli, Institute on Membrane Technology National Research Council of Italy, ITM-C, Rende, Italy Giusi, Canonaco, Comparative Neuroanatomy Lab, Italy

CFD Modeling for the Concentration of Soy Protein in an Ultrafiltration Hollow Fiber Membrane System Using Resistance-in-Series Model Rajabzadeh, Moresoli, University of Waterloo, Waterloo, Canada Marcos, Universite de Sherbrooke, Quebec, Canada

Flux Recovery During Infrasonic Frequency Backpulsing of Micro- and Ultrafiltration Membranes Fouled with Dextrin and Yeast McLachlan, Shugman, Sanderson, UNESCO Assoc Centre for Macromolecules, Stellenbosch, South Africa

11:15AM A Membrane Process to Capture CO2 from Power Plant Flue Gas Merkel, Lin, Thompson, Daniels, Serbanescu, Baker, Membrane Technology and Research, Menlo Park, California, USA

Improvement of Swimming Pool Water Quality by Ultrafiltration - Adsorption Hybrid Process Barbot, Moulin, Aix-Marseille University, France

Properties and Potential of Polymeric Nanofiber Membranes for Liquid Filtration Applications Singh, Kaur, Ramakrishna, National University of Singapore, Singapore Wun Jern, Nanyang Technological University, Singapore Matsuura, University of Ottawa, Ottawa, Canada

Membrane Emulsification Technology to Enhance Phase Transfer Biocatalyst Properties and Multiphase Membrane Reactor Performance Giorno, Mazzei, Bazzarelli, Drioli, Institute on Membrane Technology, ITM-CNR, Rende, Italy Piacentini, University of Calabria, Rende, Italy

Hydrodynamic CFD Simulation of Mixing in Full-Scale Membrane Bioreactors with Field Experimental Validation Wang, Brannock, Leslie, The University of New South Wales, Sydney, Australia

Electrostatic Contributions in Binary Protein Ultrafiltration Wang, Rodgers, University of California Riverside, Riverside, California

11:45AM Membranes and Post Combustion Carbon Dioxide Capture: Challenges & Prospects Favre, LSGC CNRS, Nancy, France

Processing of Low- and Intermediate- Level Radioactive Wastes from Medical and Industrial Applications by Membrane Methods Zakrzewska-Trznadel, Institute of Nuclear Chemistry and Technology, Warszawa, Poland

Perfluoropolymer Membranes for Gasoline Vapor Emissions Reductions Bowser, Majumdar, Compact Membrane System, Inc., Wilmington, Delaware, USA

Anti-Biofouling Membrane Surface with Grafted Zwitterionic Polysulfobetaine for Improved Blood Compatibility Chang, R&D Center for Membrane Technology, Taiwan

Hybrid Modeling: An Alternative Way to Predict and Control the Behavior of Cross-Flow Membrane Filtration Processes Curcio, Calabro, Iorio, University of Calabria, Rende, Italy

Membrane Separation of High Added Value Milk Proteins Mier, Ibanez, Ortiz, University of Cantabria, Spain

12:15PM The Effect of Sweep Uniformity on Gas Dehydration Modules Hao, Lipscomb, The University of Toledo, Toledo, Ohio, USA

Removal of Natural Organic Matter in Coagulation-Microfiltration-GAC Adsorption Systems for Drinking Water Production Ahn, KAIST, Daejeon, Korea Lee, University of Suwon, Gyeonggi-do, Korea Bae, Daejeon University, Daeion, KoreaMin, Samsung Construction, Kyunggi-Do, Korea Shin, KAIST, Daejeon, Korea

Universal Membranes for Solvent Resistant Nanofiltration (SRNF) and Pervaporation (PV) Based on Segmented Polymer Network (SPN) Li, Basko, Vankelecom, Centre for Surface Chemistry and Catalysis, Belgium Du Prez, Ghent University, Belgium

Supported Liquid Membranes with Strip Dispersion for the Recovery of Cephalexin Vilt, Ho, Ohio State University, Columbus, Ohio, USA

Artificial Neural Networks Analysis of RO Process Performance: RO Plant Performance and Organic Compound Passage Giralt, Rallo, Libotean, Giralt, Universitat Rovira i Virgili, Catalunya, Spain Cohen, University of California, Los Angeles, Los Angeles, California, USA

Tuning of the Cut-Off Curves By Dynamic Ultrafiltration Jonsson, Technical University of Denmark, Lyngby, Denmark

Page 13: Oral Proceedings

Thursday, July 17 – Morning Sessions

EMS Barrer Prize (Maui)

Chair: Andrew Livingston, Imperial College, United Kingdom Co-Chair: Tor Ove Leiknes, Norwegian University of Science and Technology, Norway

Gas Separation IV (Kaua’i)

Chair: Juin-Yih Lai, Chung Yuan Christian University, Taiwan Co-Chair: Tai-Shung (Neal) Chung, National University of Singapore, Singapore

Ultra- and Microfiltration II -

Processes (Moloka’i)

Chair: Andrew Zydney, The Pennsylvania State University, University Park, Pennsylvania, USA Co-Chair: Tony Fane, University of New South Wales, Sydney, Australia

Drinking and Wastewater

Applications IV (Honolulu/Kahuku)

Chair: Chuyang Tang, Nanyang Technological University, Singapore Co-Chair: Maria Norberta de Pinho, Instituto Superior Técnico, Portugal

Inorganic Membranes II

(O’ahu/Waialua)

Chair: Yi Hua (Ed) Ma, Worcester Polytechnic Institute, Worchester, Massachusetts, USA Co-Chair: Weishen Yang, Chineese Academy of Science, China

Fuel Cells II (Wai’anae)

Chair: Michael Guiver, National Research Council of Canada, Canada Co-Chair: Peter N. Pintauro, Case Western Reserve University, Cleveland, Ohio, USA

8:15AM My Membrane World Strathmann, Professor, Germany

8:35AM Climbing Membranes and Membranes Operations Drioli ,Institute on Membrane Technology of the Italian National Research Council, Rende, Italy

8:15AM Polymer-Based Multicomponent Membranes for Gas Separation Peinemann, GKSS-Forschungszentrum, Geesthacht, Germany

Membranes Applications in the Pulp and Paper Industry: New Developments and Case Studies Lipnizki, Alfa Laval Product Centre Membranes, Soborg, Denmark Perrson, Jonsson, Lund University, Lund, Sweden

Optimization of Bubbly Flow in Flat Sheet Membrane Modules Prieske, Drews, Kraume, Technische Universität , Berlin, Germany

High Temperature Gas Permeation Characteristics of MFI and DDR Type Zeolite Membranes Lin, Kanezashi, O’Brien, Zhu, Arizona State University, Tempe, Arizona, USA

Fuel Cell Membranes from Nanofiber Composites Wycisk, Choi, Lee, Pintaruo, Case Western Reserve University, Cleveland, Ohio, USA Mather, Syracuse University, Syracuse, New York, USA

9:00AM Coffee Break (Ballroom Foyer) 9:30AM Membrane Separation of Nitrogen

from High-Nitrogen Natural Gas: A Case Study from Membrane Synthesis to Commercial Deployment Baker, Membrane Technology and Research Inc., USA

9:30AM Gas Separation Properties of C/SiO2/Alumina Composite Membranes for CO2 Separation Han, Kim, Lee, Hanyang University, Seoul, Korea Park, University of Ulsan, Ulsan, Korea

PAA and Thiol Functionalized MF/UF Membranes for Surfactant Separation and High Value Metal Capture: Experimental Results and Modeling Ladhe, Frailie, Bhattacharyya, University of Kentucky, Lexington, Kentucky, USA

Removal of Organic Micropollutants with NF/RO Membranes: Derivation and Validation of a Rejection Model Verliefde, van Dijk, Delft University of Technology, Delft, The Netherlands Cornelissen, Heijman, Kiwa Water Research, Nieuwegein, The Netherlands Amy, UNESCO-IHE, Delft, The Netherlands Van der Bruggen, University of Leuven, Leuven, Belgium

Adding Ion-Selective Functionality to Desalination Membranes with Unique Charge and Structural Properties of MFI Silicalite and ZSM-5 Zeolites Duke, Victoria University, Melbourne, Australia Lin, Arizona State University, Tempe, Arizona, USA Diniz da Costa, The University of Queensland, St. Lucia, Australia

Hybrid Nanocomposite Membranes for PEMFC Applications Lafitte, Niepceron, Bigarre, Galiano, Commissariat à l’Energie Atomique, Monts, France

9:55AM Molecular Simulations of Membrane Transport Processes Vegt, Max Planck Institute for Polymer Research, Mainz, Germany

10:00AM Gas Transport Properties of Hyperbranched Polyimide Silica Hybrid Membranes Yamada, Kyoto Institute of Technology, Kyoto, Japan Itahashi, Suzuki, Nagoya Institute of Technology, Nagoya, Japan

Assuring Biodiesel Quality via Selective Membrane Filtration Gutierrez-Padilla, Downs, Pellegri o, University of Colorado, Boulder, Colorado, USA Bzdek, Sybios Technology, LLC, Fort Collins, Colorado, USA

Anaerobic Membrane Bioreactor (AnMBR) for Landfill Leachate Treatment and Removal of Hormones Yeh, Do, Prieto, University of South Florida, Tampa, Florida, USA

Carbonate-Ceramic Dual-Phase Membrane for High Temperature Carbon Dioxide Separation Anderson, Lin, Arizona State University, Tempe, Arizona, USA

Hybrid Self-Organized Membranes: New Strategies for Promising Fuel Cell Energy Applications Barboiu, Michau, Institut Europeen des Membranes, Montpellier, France

10:20AM Beyond Academic Research Koops, GE Water, Burlington, Ontario, Canada

10:45 New Challenges in Membrane Preparation by Phase Inversion Technique Figoli, ITM-CNR, Rende, Italy

10:30AM Carbon Membranes Tackling the Aging Issue Sheridan, Lie, He, Hagg, Norwegian University of Science and Technology, Trondheim, Norway

High Oxidative Resistant PVDF UF Membrane for Metal-CMP Wastewater Treatment Shiki, Furumoto, Asahi Kasei Chemicals, Suizuoka, Japan

Comparison of Multi-Parameter Optimization Strategies for the Development of Nanofiltration Membranes for Salt and Micropollutants Removal Cano-Odena, Vandezande, Cools, Vanderschoot, De Grave, Ramon, De Raedt, Vankelecom, Katholieke Universiteit Leuven, Leuven, Belgium

High Quality Tubular Silica Membranes for Gas Separation Luiten, Huiskes, Kruidhof, Nijmeijer, University of Twente, The Netherlands

Ion-Exchange Membranes from Side-Chain Sulfonated Poly(arylene ether)s Meier-Haack, Schlenstedt, Butwilowski, Vogel, Leibniz Institute of Polymer Research Dresden, Dresden, Germany

11:10AM Considerations for Normal Flow Filtration: Fouling Models, Modules and Systems Kools, Millipore Coportation, Billerica, Massachusetts, USA

11:00AM Glassy Perfluoropolymer - Zeolite Hybrid Membranes for Gas and Vapor Separations Golemme, Univ. Della Calabria; ITM-CNR; and INSTM, Rende, Italy Muoio, De Luca, Bruno, Manes, Univ. della Calabrai, Rende, Italy Choi, Tsapatsis, Universtiy of Minnesota, Minneapolis, Minnesota

Hygienic Barrier Efficiency of a Coupled Coagulation / Flocculation and Ceramic Microfiltration System for Potable Water Production Meyn, Leiknes, Norwegian University of Science and Technology, Trondheim, Norway Konig, Technical University Berlin, Berlin, Germany

Study of an External MBR for Degradation of Endocrine Disrupter 17(alpha)-ethinylestradiol Clouzot, Marrot, Doumenq, Roche, University of Aix-Marseille, France

Recent Developments on the Preparation and Modeling of Nanoporous Silicon Carbide Membranes for Gas Separation Applications Mourhatch, Elyassi, Chen, Sahimi, Tsotsis, University of Southern California, Los Angeles, California, USA

Ionomer Blend Membranes for Low T and Intermediate T Fuel Cells Kerres, Schoenberger, Schaefer, Chromik, Krajinovic, University of Stuttgart, Stuttgart, Germany Gogel, Jorissen, Zentrum fur Sonnenenergie- und Wasserstoff-Forschung, Ulm, Germany Li, Jensen, Bjerrum, Technical University of Denmark, Lyngby, Denmark

11:35AM Dialysis Membranes - Continuous Improvements Krause, Storr, Gohl Gambro Dialysatoren GmbH

11:30AM Development and Characterization of PPO-based Emulsion Polymerized Mixed Matrix Membranes Kruczek, Wang, Tremblay, University of Ottawa, Ottawa, Ontario, Canada Sadeghi, Natural Resources Canada, Varennes, Quebec, Canada

Pioneering Explorations of Rooting Causes for Morphology and Performance Differences in Hollow Fiber Kidney Dialysis Membranes Spun From Linear and Hyperbranched Polyethersulfone Yang, Chung, National University of Singapore, Singapore Weber, Warzelhan, BASF Aktiengesellschraft

Pressurized and De-pressurized Membrane Photoreactors for Removal of Pharmaceuticals from Waters Molinari, Caruso, Argurio, Poerio, University of Calabria, Rende, Italy

Preparation and Gas Separation Performance of Carbon Hollow Fiber Membrane Module Yoshimune, Haraya, AIST, Tsukuba, Japan

Hygrothermal Aging of Nafion Thominette, Collette, ENSAM, Paris, France Gebel, CEA, Grenoble, France

12:00PM On the Origin of the Overlimiting Current in Electrodialysis Wessling, University of Twente, Netherlands

12:00PM Novel Semi-IPN Carbon Membranes Fabricated by a Low-Temperature Pyrolysis for C3H6/C3H8 Separation Chng, Xiao, Chung, National University of Singapore, Singapore Toriida, Tamai, Mitsui Chemicals, Inc. , Japan

Pressurized Porous Nanocrystalline Silicon Membranes Exhibit High Permeability to Water and Gas Gaborski, Fang, Striemer, Kavalenka, Snyder, Hoffman, DesOrmeaux, McGrath, University of Rochester, Rochester, New York, USA Fauchet, SIMPore, West Henrietta, New York, USA

Mechanisms Governing the Effects of Membrane Fouling on the Nanofiltration of Micropollutants Nghiem, Espendiller, University of Wollongong, Wollongong, Australia Braun, University of Applied Science Cologne, Cologne, Germany

Viability of ITM Technology for Oxygen Production and Oxidation Processes: Material, System and Process Aspects den Exter, Haije, Vente, Energy research Centre of the Netherlands, Petten, The Netherlands

Automotive Hydrogen Fuel Cell Membrane Applications Brenner, Coms, Gittleman, Jiang, Lai, Nayar, Schoeneweiss, Zhang, General Motors, Honeoye Falls, New York, USA

Page 14: Oral Proceedings

Thursday, July 17 – Afternoon Sessions

12:30PM Lunch Break Hybrid and Novel

Processes II (Kaua’i)

Chair: Glenn Lipscomb, University of Toledo, USA Co-Chair: Hans Wijmans, Membrane Technology & Research, USA

Membrane Fouling – RO & Biofouling

(Maui)

Chair: Isabel Escobar, University of Toledo, USA Co-Chair: Vicki Chen, UNESCO, University of New South Wales, Australia

Pervaporation and Vapor Permeation II

(Moloka’i)

Chair: Richard Baker, Membrane Technology & Research, USA Co-Chair: Tadashi Uragami, Kansai University, Japan

Desalination II (Honolulu/Kahuku)

Chair: Eric Hoek, UCLA, Los Angeles, USA Co-Chair: Raphael Semiat, Technion – Israel Inst. of Tech., Israel

Membrane and Surface Modification II (O’ahu/Waialua)

Chair: Sung Soo Kim, Kyunghee University, Korea Co-Chair: Young Moo Lee, Hanyang University, Korea

Hybrid Membranes (Wai’anae)

Chair: William J. Koros, Georgia Institute of Technology, USA Co-Chair: Tim Merkel, Membrane Technology & Research, USA

2:15PM Cyclic Hybrid Adsorbent-Membrane Reactor (HAMR) Studies for Hydrogen Production Tsotsis, Harale, Hwang, Liu, Sahimi, University of Southern California, Los Angeles, California, USA

Biofouling of Spiral Wound Nanofiltration and Reverse Osmosis Membranes: A Feed Spacer Problem Vrouwenvelder, Van Loosdrecht, Wetsus, Delft University of Technology, Delft, The Netherlands Graf von der Schulenburg, Johns, University of Cambridge, Cambridge, United Kingdom Kruithof, Westus Centre of Excellence for Sustainable Water Technology, Leeuwarden, The Netherlands

Aromatics Control in Refining with Pervaporation White, Harding, W.R. Grace & Co.-Conn., Columbia, Maryland, USA

Memstill: A Near-Future Technology for Sea Water Desalination Dotremont, Ho, Keppel Environmental Technology Centre Kregersman, Puttemans, Keppel Seghers Belgium NV, Williebroek, Belgium Hanemaaijer, TNO Science and Industry, The Netherlands

Macroporous Membrane Adsorbers with Tailored Affinity and High Capacity via Photo-Initiated Grafting-of Functional Polymer Layers Ulbricht, He, Wang, Yang, Yusof, Universität Duisburg-Essen, Essen, Germany

Polymer-Zeolite 4A Mixed-Matrix Nanocomposite Gas Separation Membranes Tantekin-Ersolmaz, Kertik, Agil, Atalay-Oral, Istanbul Technical University, Istanbul, Turkey

3:00PM Nanoparticle-Enhanced Microfiltration for Low Energy Metal Removal from Water Jawor, Hoek, University of California Los Angeles, Los Angeles, California, USA

Microbial-Sensing Membranes Functionalized with a Temperature Sensitive Polymer Film Gorey, Escobar, Gruden, University of Toledo, Toledo, Ohio, USA

Membrane Based Liquid Fuels Desulfurization Process for Point-of-Use Applications Aagesen, Swamy, Intelligent Energy Inc., Long Beach, California, USA

Parameters Affecting Osmotic Backwash Sagiv, Avraham, Dosoretz, Semiat, Grand Water Research Institute, Technion, Haifa, Israel

Surface Modification of Pervaporation Membrane by UV-Radiation and Application of Shear Stress Izák, Institute of Chemical Process Fundamentals, Prague, Czech Republic Godinho, Crespo, Universidade Nova de Lisboa, Portugal Brogueira, Figueirinhas, Instituto Superior Tecnico, Portugal

Hollow Fillers For Flux Enhancement In Mixed Matrix Membranes Vanherck, Aldea, Aerts, Martens, Vankelecom, Katholieke Universiteit Leuven, Heverlee, Belgium

3:30PM Crystallization in Hollow Fiber Devices Zarkadas, Shering, Plough Institute, Union, New Jersey, USA Sirkar, New Jersey Institute of Technology, Newark, New Jersey, USA

Modification of Microfiltration Membranes: Implications for Biofouling, Flux Recovery and Antibacterial Properties Malaisamy, Jones, Howard University, Washington, District of Columbia, USA Holder, Raskin, Berry, University of Michigan, Ann Arbor, Michigan, USA Lepak, Cornell University, Ithaca, New York, USA

Ion-containing Polyimide Membranes : A Way of Overcoming the Trade-off Permeability in Pervaporation? Jonquieres, Awkal, Clement, Lochon, Nancy Universite, France

Fabrication of High Performance Dual Layer Hydrophilic-Hydrophobic Hollow Fiber Membranes for Membrane Distillation Process Bonyadi, Chung, National University of Singapore, Singapore

Microstructured Hollow Fiber Membranes for Ultrafiltration Wessling, Culfaz, Jani, Lammertink, University of Twente, The Netherlands

Elaboration and Characterization of a Hybrid Membrane Based on Hydrophilic Polymer/Ceramic Membrane for Metal Affinity Chromatography Paolucci-Jeanjean, Dubois, Muvdi Nova, Belleville, Rivallin, Barboiu, Institut Européen des Membranes, Montpellier, France Bacchin, Laboratoire de Genie Chimique, Toulouse, France

4:00PM Selectivity between Potassium, Sodium, and Calcium Ions in Synthetic Media and Juice Media Using Water Enhanced- Electrodeionization Ho, Cross, Hestekin, Kurup, Universtiy of Arkansas, Arkansas, USA

Role of Seawater Chemistry in Algal Biopolymer Fouling of Seawater RO Membranes Jin, Hoek, University of California Los Angeles, Los Angeles, California, USA

Study of the Effect of Framework Substitution on the Pervaporation of Xylene Isomers Through MFI-type Zeolite Membranes O'Brien-Abraham, Lin, Arizona State University, Tempe, Arizona, USA

A New Niche for Electrodialysis: Improving Recovery from RO Desalination Lawler, Kim, Walker, University of Texas, Austin, Texas, USA

High Performance Surface Nano-Structured RO/NF Membranes Lin, Lewis, Kim, Cohen, University of California, Los Angeles, California, USA

Optimization of SRNF Membranes Cast from Emulsified Polyimide Solutions: Comparison of a Traditional Approach with a High Throughput/Combinatorial Approach Vandezande, Vanlelecom, Katholieke Universiteit Leuven, Leuven, Belgium Gevers, Flemish Institute for Technological Research, Mol, Belgium Weyens, Department of Chemistry-Biology-Geology, Diepenbeek, Belgium

4:30PM Capillary ElectroChromatography and Membrane Technology: Merging the Advantages Kopec, Stamatialis, Wessling, University of Twente, The Netherlands

Effect of Surface Charge and pH on Fouling and Critical Flux of MF Membranes during Protein Filtration Meier-Haack, Leibniz Institute of Polymer Research Dresden, Dresden, Germany

On the Unusual Transport Phenomena of Vapours in Amorphous Glassy Perfluoropolymer Membranes with High Fractional Free Volume Jansen, Tocci, Drioli, Institute on Membrane Technology, Rende, Italy Friess, Institute of Chemical Technology, Prague, Czech Republic

A Novel Three-Stage Treatment for Brackish Water Reverse Osmosis Concentrate: Parameter Effects on and Feasibility of Antiscalant Oxidation Greenlee, Lawler, Freeman, The University of Texas at Austin, Austin, Texas, USA Marrot, Moulin, Universite Paul Cezanne, France

Characterization of Commercial Reverse Osmosis Membrane Performance and Surface Modification to Enhance Membrane Fouling Resistance Van Wagner, Freeman, Sharma, University of Texas at Austin, Austin, Texas, USA

Crosslinking and Stabilization of MgO Filled PTMSP Nanocomposite Membranes for Gas Separation Shao, Hagg, Norwegian University of Science and Technology, Trondheim, Norway

5:00PM Chitosan Chiral Ligand Exchange Membranes for Sorption Resolution of Amino Acids Chu, Wang, Xie, Yang, Song, Sichuan University, Sichuan, China Niu, University of Seaskatchewan, Saskatoon, Canada

Synthesis and Evaluation of Novel Biocidal Coatings to Reduce Biofouling on Reverse Osmosis Membranes Hibbs, McGrath, Altman, Sandia National Laboratories, Albuquerque, New Mexico, USA Cornelius, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA Kang, Adout, Elimelech, Yale University, New Haven, Connecticut, USA

Pervaporation Performance of PDMS-grafted Aromatic Polyamide Membrane Exhibiting High Durability and Processability Yun, Nagase, Tokai University

Sustainable Seawater Desalination: Small Scale Windmill and RO-System Heijman, Rabinovitch, van Diijk, Delft University of Technology, Delft, The Netherlands

Hydrophobic Modified Ceramic Membranes for Gas Separation and Desalination Cerneaux, Condom, Persin, Prouzet, Larbot, Institut Européen des Membranes, Montpellier, France

Preparation High Performance Microporous/Mesoporous Hybrid Membranes for Gas Separation Liu, Zhao, Wang, Liu, Qiu, Dalian University of Technology, Dalian, China Cao, Dalian Institute of Chemical Physics, Dalian, China

Page 15: Oral Proceedings

Friday, July 18 – Morning Sessions

8:00AM Plenary III (Hawai’i Ballroom): Dr. William E. Mickols (DOW Water Solutions, Edina, Minnesota, USA)

The Development of Reverse Osmosis and Nanofiltration through Modern Times 9:00AM Coffee Break (Ballroom Foyer)

Gas Separation V (Kaua’i)

Chair: Tai-Shung (Neal) Chung, National University of Singapore, Singapore Co-Chair: Juin-Yih Lai, Chung Yuan Christian University, Taiwan

Nanofiltration and Reverse Osmosis III -

Applications (Maui)

Chair: William Mickols, Dow Water Solutions, USA Co-Chair: Ho Bum Park, Ulsan University, Korea

Membrane Fouling – RO & Desalination

(Moloka’i)

Chair: Vicki Chen, UNESCO, University of New South Wales, Australia Co-Chair: Pierre Le-Clech, UNESCO, University of New South Wales, Australia

Membrane and Surface Modification III

(Honolulu/Kahuku)

Chair: Mathias Ulbricht, Lehrstuhl fur Technische, Germany Co-Chair: Sung Soo Kim, Kyunghee University, Korea

Inorganic Membranes III

(O’ahu/Waialua)

Chair: Jerry Y. S. Lin, Arizona State University, USA Co-Chair: Yi Hua (Ed) Ma, Worcester Polytechnic Institute, USA

Facilitated Transport Membranes (Wai’anae)

Chair: Yong-Soo Kang, Hanyang University, Korea Co-Chair: Jongok Won, Sejong University, Korea

9:30AM Designing Membranes for Future Membrane Gas Separation Applications Baker, Membrane Technology and Research, Inc., Menlo Park, California, USA

Fundamental Study and Performance Advancement of Seawater RO Membrane Henmi, Tomioka, Kawakami, Kurihara, Toray Industries, Inc., Shiga, Japan

Studies on CaSO4 and CaCO3 Scaling of Membranes in Desalination by DCMD Sirkar, He, New Jersey Institute of Technology, Newark, New Jersey, USA Gilron, Zuckerberg Institute for Water Research, Beer-Sheva, Israel

Modification of Polyethersulfone Nanofiltration Membranes Bruggen, Schols, Boussu, K.U.Leuven, Heverlee, Belgium

Silica Network Engineering For Highly Permeable Hydrogen Separation Membranes Tsuru, Yada, Kanezashi, Hiroshima University, Hiroshima, Japan

Facilitated Transport Membrane for Selective Separation of CO2 from CO2-H2 Mixtures at Elevated Temperatures and Pressures Teramoto, Yegani, Matsuyama, Kobe University, Kobe, Japan Okada, Renaissance Energy Research Co., Osaka, Japan

10:15AM Sorption and Dilation of Crosslinked Poly(ethylene oxide) Membranes by Carbon Dioxide and Ethane Ribeiro, Freeman, University of Texas at Austin, Austin, Texas, USA

Development and Testing of a High-Capacity, Mobile Desalination System Miller, Shalewitz, U.S. Army TARDEC, Port Hueneme, California, USA Chapman, Bureau of Reclamation, Denver, Colorado, USA Barley, Blumenstein, NSF International, Ann Arbor, Michigan, USA

Development of Fouling Index to Access Colloidal Fouling in Reverse Osmosis Unit for Water Reclamation Sim, Ye, Chen, Fane, UNESCO Center for Membrane Science and Technology, Sydney, Australia

Development and Characterization of Ceramic Microfiltration Membrane Devices for Biomolecule Separation Malaisamy, Jones, Howard University, Washington DC, USA Lepak, Spencer, Cornell University, Ithaca, New York, USA

Development of Novel CO2 Affinity-Enhanced Carbon Membranes: Characterization and CO2 Separation Performance Kai, Kazama, Fujioka, Research Institute of Innovative Technology for the Earth (RITE), Kyoto, Japan

Explorative Investigation of Cu(II) Facilitated Transportation Through Supported Liquid Membrane and Its Derivatively Successful Story Yang, Chung, Jiang, Kocherginsky, National University of Singapore, Singapore

10:45AM Kinetic Sorption and Permeation Behavior of Water Vapor in Polymeric Membranes Nymeijer, Potreck, Nymeijer, Wessling, University of Twente, The Netherlands Van Marwijk, Heijboer, KEMA, The Netherlands

Investigation of Amphoteric Polybenzimidazole (PBI) Nanofiltration Hollow Fiber Membrane for Both Cation and Anion Removal Wang, Lv, Chung, National University of Singapore, Singapore

The Effect of Membrane Body Conductance on the Zeta Potential of Clean and Fouled Polymer Membranes Luxbacher, Anton Paar GmbH, Austria Comerton, Andrews, University of Toronto, Toronto, Canada Bagley, University of Wyoming, Laramie, Wyoming, USA

Solvent Resistant Nanofiltration with Partially Hydrolyzed Asymmetric Polyacrylonitrile Membranes Vandezande, Li, Vanderschoot, Willems, Vankelecom, Centre for Surface Chemistry and Catalysis, Belgium

Electronic Conduction and Oxygen Permeation Through Mixed-Conducting SrCoFeO(x) Membranes Kniep, Lin, Arizona State University, Tempe, Arizona, USA

Ionic Liquid Membranes for Carbon Dioxide Separation Myers, Pennline, Luebke, US DOE, National Energy Technology Laboratory, Pittsburgh, Pennsylvania, USA Ilconich, Parsons, South Park, Pennsylvania, USA

11:15AM Natural Gas Purification Using High Performance Crosslinked Hollow Fiber Membranes: Effects of High Pressure CO2 and Toluene Feed Omole, Koros, Georgia Inst. of Tech., Atlanta, Georgia, USA Miller, Richmond, California, USA

Nanofiltration of Ferric and Ferrous Cations in Acidic Solutions Bernat, Stuber, Bengoa, Fabregat, Font, Universitat Rovira i Virgili, Tarragona, Spain Fortuny, Universitat Politecnica de Catalunya, Barcelona, Spain

Mechanisms of Marine Bacteria Adhesion to Seawater RO Membranes Huang, Hoek, University of California Los Angeles, Los Angeles, California, USA

Hydrophilic Modification of Polypropylene Hollow Fiber Membrane Kim, Kim, Kim, Kyung Hee University, Gyeonggido, Korea

Micro-Structured Inorganic Membrane Reactor Liu, Wang, Elliott, Li, Johnson, Zheng, Pacific Northwest National Lab, Richland, Washington, USA

CO2 Capture: Reduction in Greenhouse Gas Levels Trachtenberg, Smith, Cowan, Carbozyme, Inc., Monmouth Junction, New Jersey, USA

11:45AM Synthesis and Gas Permeability of Hyperbranched Polyimide Membranes Nagai, Meiji University, Kawasaki, Japan

Treatment of the Groundwater Contaminated by High Concentration of Arsenic Alizadehfard, WorleyParsons, Australia Alizadehfard, Curtin University, Bentley, Australia

Optical Monitoring and Real-Time Digital Image Analysis of Mineral Scale Formation on RO Membranes Kim, Lyster, Cohen, University of California Los Angeles, Los Angeles, California, USA

Effect of Surface Modifying Macromolecules Stoichiometric Ratio on Composite Hydrophobic/Hydrophilic Membranes Characteristics and Performance in Membrane Distillation Qtaishat, Matsuura, University of Ottawa, Ottawa, Canada Khayet, University of Complutense Madrid, Madrid, Spain

Selective Gas Transfer and Catalytic Processes in Nano-Channels of Ceramic Catalytic Membranes Teplyakov, Tsodikov, A.V.Topchiev Institute of Petrochemical Synthesis, RAS, Moscow, Russia Moiseev, Kurnakov Institute of General and Inorganic Chemistry, RAS, Moscow, Russia

Novel Olefin Carrier for Facilitated Transport Membranes: Partially Polarized Surface of Silver Nanoparticles by Electron Acceptor Kang, Kang, Hanyang University, Korea

12:15PM The Effect of Water on the Gas Separation Performance of Polymeric Membranes for Carbon Dioxide Capture Kentish, Scholes, Hasan, Stevens, CRC for Greenhouse Gas Technologies, Victoria, Australia

Purification of Glucose/Sodium Lactate Solutions by Nanofiltration: Selectivity Improvement by the Addition of a Mineral Salt Roux-de Balmann, Galier, Université de Toulouse, Toulouse, France Umpuch, Kanchanatawee, Nakhon Ratchasima, Thailand

Effect of Foulant-Foulant Interaction on the Limiting Flux for RO and NF Membranes during Organic Fouling Model Development and AFM Adhesion Force Measurement Tang, Nanyang Tech. Univ., Thailand Nam Kwon, Leckie, Stanford University, Palo Alto, California, USA

Surface Modification of an Aromatic Polyamide Membrane by Self-Assembly of Polyethyleneimine on the Membrane Surface Zhou, Feng, University of Waterloo, Waterloo, Canada Yu, Zhejiang Sci-Tech University, China Gao, The Development Center of Water Treatment Technology, China

The Oxidative CO2 Reforming of Methane to Syngas in a Thin Tubular Mixed-Conducting Membrane Reactor Zhang, Dong, Jin, Xu, Nanjing University of Technology, China

Selectivity and Stability of Facilitated Transport Membranes Containing Silver Nanoparticles for Propylene Separation Pollo, Habert, Borges, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil

Page 16: Oral Proceedings

Friday, July 18 – Afternoon Sessions

12:45PM Lunch Break Pervaporation and

Vapor Permeation III (Kaua’i)

Chair: Tadashi Uragami, Kansai University, Japan Co-Chair: Ivy Huang, Membrane Technology and Research, Inc., USA

Drinking and Wastewater

Applications V (Maui)

Chair: Daniel Yeh, University of South Florida, USA Co-Chair: Chuyang Tang, Nanyang Technological University, Singapore

Fuel Cells III (Moloka’i)

Chair: James McGrath, Virginia Tech, USA Co-Chair: Michael Guiver, National Research Council of Canada, Canada

Ultra- and Microfiltration III -

Membranes (Honolulu/Kahuku)

Chair: Willem Kools, Millipore, Inc., USA Co-Chair: Andrew Zydney, The Pennsylvania State University, USA

Membrane Contactors (O’ahu/Waialua)

Chair: Pierre Cote, Vaperma, Canada Co-Chair: Kitty Nijmeijer, University of Twente, The Netherlands

Packaging and Barrier Materials (Wai’anae)

Chair: Anne Hiltner, Case Western Reserve University, USA Co-Chair: Eric Baer, Case Western Reserve University, USA

2:15PM Vapor Permeation and Pervaporation as Efficient Alternatives in the Recovery of Fruit Aroma Compounds Ortiz, Diban, Urtiaga, University of Cantabria, Stantander, Spain

The Development of a Household Ultrafiltration System for Developing Countries Peter-Varbanets, Vital, Hammes, Pronk, Eawag - Swiss Federal Institute of Aquatic Science and Technology, Duebendorf, Switzerland

Crystalline Order and Membrane Properties in Perfluorosulfonate Ionomers for PEMFC Applications Moore, Virginia Tech, Blacksburg, Virginia, USA

Pilot-scale Integrity Monitoring of Microfiltration Processes Using a Novel Multi-membrane Sensor Wong, Wai, Su, Advanced Water and Membrane Centre, Institute of Environmental Science, Singapore Fane, Nanyang Tech. Univ., Singapore Phattanarawik, Norwegian Univ. of Sci. and Tech., Norway

Modelling Aroma Stripping Under Various Forms of Membrane Distillation Processes Jonsson, Technical University of Denmark, Lyngby, Denmark

New Developments in the Measurement of Multi-Component Sorption in Barrier Polymer Materials: A Key Step Towards the Modeling of Fuel Tank Permeability Jonquieres, Clement, Kanaan, Lenda, Lochon, Nancy Universite, Nancy France Brule, Arkema, Serquigny, France

3:00PM Monitoring and Modelling of Aroma Recovery from Fermentation Media Using Pervaporation and Fractionated Condensation Brazinha, Teodoro, Crespo, Universidade Nova de Lisboa, Caparica, Portugal

Treatment Performance and Detoxification of Coke Plant Wastewater Using an Anaerobic-Anoxic-Oxic Membrane Bioreactor System Zhao, Huang, Lee, He, Division of Water Environment, Department of Environmental Science and Engineering, Taiwan

Model Studies of the Characterization of the Durability of Nafion® Membranes and Nafion/Inorganic Oxide Nanocomposite Membranes Mauritz, Hassan, Patil, Rhoades, University of Southern Mississippi

Integrity Monitoring for Membrane Bioreactor Systems through Turbidity and SDI Measurement Zha, Kippax, Phelps, Nguyen, Siemens Water Techologies, South Windsor, Australia

Membrane Extraction for Acetic Acid and Lignin Removal from Biomass Hydrolysates Wickramasinghe, Grzenia, Colorado State University, Fort Collins, Colorado, USA Schell, National Renewable Energy Laboratory, Golden, Colorado, USA

Fundamental Exploration of Metal-Catalyzed Oxidation in Styrene-Butadiene-Styrene Block Copolymers Tung, Ferrari, Li, Ashcraft, Freeman, Paul, The University of Texas at Austin, Austin, Texas, USA

3:30PM Effect of Feed Solution Characteristics on Flavour Concentration by Pervaporation Overington, Wong, Harrison, Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand Ferreira, Fonterra Co-Operative Group, Ltd., Auckland, New Zealand

Time Course of Sub-Micron Organic Matter in MBRs: Relation to Membrane Fouling in MBRs Kimura, Yamato, Miyoshi, Naruse, Watanabe, Hokkaido University, Sapporo, Japan

PBI Polymers for High Temperature PEM Fuel Cells Benicewicz, University of South Carolina, USA

Membrane Characterisation : Assessment of the Bacterial Removal Efficiency LeBleu, Causserand, Roques, Aimar, Université de Toulouse, Toulouse, France

Operational Flexibility of Gas-Liquid Membrane Contactors for CO2 Separation Fischbein, Nijmeijer, Wessling, University of Twente, Enschede, The Netherlands

The Effect of Reaction Conditions on Oxidation of Metal-catalyzed Poly(1,4-butadiene) Li, Tung, Freeman, The University of Texas at Austin, Austin, Texas, USA Stewart, Jenkins, Global PET Technology, Eastman Chemical Company, Kingsport, Tennessee, USA

4:00PM Concentration of Bioethanol by Porous Hydrophobic Membranes Uragami, Kansai University, Osaka, Japan

On the Lookout for A Fouling Indicator A Critical Evaluation of Various Methods for Fouling Characterisation in MBR Drews, TU Berlin, Berlin, Germany

Novel Electrolytes for Fuel Cell Electrodes Muldoon, Hase, Toyota Motor Engineering & Manufacturing, Ann Arbor, Michigan, USA Pintauro, Lin, Wycisk, Case Western Reserve University, Cleveland, Ohio, USA

Pore Size Determination of UF and MF Membranes By Streaming Potential Measurement Nakamura, Yokohama National University, Yokohama, Japan

Effect of Spacer, Baffled and Modified Hollow Fiber Geometries in the Membrane Distillation Process Chung, Bonyadi, Teoh, National University of Singapore, Singapore Gryta, Szczecin University of Technology, Szczecin, Poland

On the Nature of Gas Barrier of Ethylene Vinyl Alcohol Copolymers Nazarenko, Chigwada, Brandt, Olson, University of Southern Mississippi, Hattiesburg, Mississippi, USA Jamieson, Case Western Reserve University, Cleveland, Ohio, USA

4:30PM Treatment of Gas Containing Hydrophobic VOCs by a Hybrid Absorption-Pervaporation Process: The Case of Toluene Carretier, Moulin, Université Paul Cézanne Aix Marseille, Provence, France Heymes, Manno-Demoustier, Fanlo, LGEI, Ecole des Mines d’Ales, Ales, France

Importance of Membrane Reactor Design for Membrane Performance in Biofilm-MBR Ivanovic, NTNU- Norwegian University of Science and Technology, Trondheim, Norway

Effect of Hydrocarbon Ionomer on Electrochemical Performance of MEA for Direct Methanol Fuel Cell (DMFC) Lee, Lee, Lee, School of Chemical Engineering, Hanyang University, Korea

Acoustic Investigation of Porous and Membrane Structures Wyart, Bonnet, Moulin, Université Paul Cézanne Aix Marseille, Provence, France Leoni, Allouche, Ecole Centrale, Marseille, France

Direct Contact Membrane Distillation: Studies on Novel Hollow Fiber Membranes, Devices, Countercurrent Cascades and Scaling Sirkar, Song, Lee, He, Li, Kosaraju, New Jersey Institute of Technology, Newark, New Jersey, USA Gilron, Zuckerberg Institute for Water Research, Beer-Sheva, Israel Ma, Liao, Irish, United Technologies Research Center, East Hartford, Connecticut

Confined Crystallization of PEO in Nanolayered Films for Improved Gas Barrier Wang, Hiltner, Baer, Case Western Reserve University, Cleveland, Ohio, USA Freeman, The University of Texas at Austin, Austin, Texas, USA

5:00PM Ellipsometric Observation of Ceramic Membranes Wyart, Tamime, Siozade, Deumie, Moulin, Université Paul Cézanne Aix Marseille, Provence, France

MEMFRAC - A New Approach to Membrane Distillation Sanchez, TNO (Netherlands Organisation for Applied Scientific Research), Delft, The Netherlands

Relationship between Biaxial Orientation and Oxygen Permeability of Polypropylene Film Lin, Dias, Hiltner, Baer, Case Western Reserve University, Cleveland, Ohio, USA Chen, The Dow Chemical Company, Freeport, Texas, USA

Page 17: Oral Proceedings

Oral Presentation Abstracts

Morning Session

Monday, July 14, 2008

Page 18: Oral Proceedings

Plenary Lecture I Monday July 14, 8:00 AM-9:00 AM, Hawai’i Ballroom

Fuel Cell Polymer Electrolyte (PEM) Derived from Disulfonated Random and Block Poly(Arylene Ether) Copolymer System Professor James E. McGrath, Virginia Tech, Blacksberg, VA, USA Our research group has been engaged in the past few years in the synthesis of biphenol based partially disulfonated poly(arylene ether sulfone) random copolymers as potential PEMs. This series of polymers has been named as BPSH-xx, where BP stands for biphenol, S stands for sulfonated, H stands for acidified and xx represents the degree of disulfonation. All of these sulfonated copolymers phase separate to form nano scale hydrophilic and hydrophobic morphological domains. The hydrophilic phase containing the sulfonic acid moieties causes the copolymer to absorb water. Water confined in hydrophilic pores in concert with the sulfonic acid groups serve the critical function of proton (ion) conduction and water transport in these systems. Both Nafion and BPSH show high proton conductivity at fully hydrated conditions. However proton transport is especially limited at low hydration level for the BPSH random copolymer. It has been observed that the diffusion coefficients of both water and protons change with the water content of the pore. This change in proton and water transport mechanisms with hydration level has been attributed to the solvation of the acid groups and the amount of bound and bulk-like water within a pore. At low hydration levels most of the water is tightly associated with sulfonic groups and has a low diffusion coefficient. This results in an isolated domain morphology. Thus, although there may be significant concentrations of protons, the transport is limited by the discontinuous morphological structure. Hence the challenge lies in how to modify the chemistry of the copolymers to obtain significant protonic conductivity at low hydration levels. This has been possible by altering the chemical structure to afford nanophase separated ion containing block or segmented copolymers. Unlike the BPSH statistical or random copolymers, where the sulfonic acid groups are randomly distributed along the chain, the multi block copolymers feature an ordered sequence of hydrophilic and hydrophobic segments. Connectivity is established between the hydrophilic domains in these multi-block copolymers, they will not need as much water, and hence will show much better protonic conductivity than the random copolymers (with similar degree of sulfonation, or IEC) at partially hydrated conditions. This is particularly valuable for H2/air systems and the self assembling nanophase also has potential for direct methanol fuel cells (DMFC) for portable power. The systhesis and characterization of these materials and their potential applications will be described.

Page 19: Oral Proceedings

Gas Separation I – 1 – Keynote

Monday July 14, 9:30 AM-10:15 AM, Kaua’i

Beyond Inorganic-Organic Nanocomposites for Molecular Separations

M. Wessling (Speaker), University of Twente, the Netherlands, [email protected]

Over the past two decades, hybrid materials comprising a polymer matrix with embedded micrometer sized inorganic particles have been developed with respect to their mass transport properties. The particles may be permeable as in the case of zeolites and have a beneficial effect on the separation properties. Impermeable particles often improve barrier properties. Smaller sub-micron sized impermeable particles, such as nano-sized silica, increase the free-volume at the particle-polymer interface, which results in an increase of permeability and so-called inverse selective separation properties.

This presentation focuses on the molecular separation properties of nano-composite materials other than inorganic-organic. Three systems will be discussed in detail: * fullerene-modified polyphenylene oxide PPO: Why is binding better than dispersing? * Dendrimer-modified polymers: a supramolecular toolbox with benefits? * Segmented block-copolymers: how does the interface of the soft and hard blocks influence molecular separations? The presentation will reflect on other nanocomposite materials and their potential for molecular separations.

Page 20: Oral Proceedings

Gas Separation I – 2

Monday July 14, 10:15 AM-10:45 AM, Kaua’i

Tailor Made Polymeric Membrane Based on Segmented Block Copolymer for CO2 Separation

A. Car (Speaker), University of Maribor, Faculty of Chemistry and Chemical Engineering, Slovenia, [email protected] C. Stropnik, University of Maribor, Faculty of Chemistry and Chemical Engineering, Slovenia W. Yave, Institute of Polymer Research, GKSS Research Centre Geesthacht GmbH, Germany K. Peinemann, Institute of Polymer Research, GKSS Research Centre Geesthacht GmbH, Germany

The use of polymers in applications that require control of gas transport is rapidly growing. For many of them, it may be desirable to utilize heterogeneous polymer blends or block copolymers in which one component provides desired permeability characteristics, while the other improves material properties (e.g., modulus or impact strength). Heterogeneous block copolymers provide the potential for creating new materials for applications with mechanical and transport properties superior to those of the parent homopolymers. Morphological features of microphase- separated block copolymers that can affect small molecules transport, include the small size and narrow size distribution of domains. Knowledge of the relationships between block copolymer morphology and the diffusion and permeation processes is essential for successful manufacturing and usage of heterogeneous polymers and their blends.

Poly(ethylene(oxide)-poly(butylene terephthalate) (PEO-PBT) multiblock copolymers are found under the commercial name Polyactive®, and they are considered as semicrystalline polymers [1]. In these copolymers, PEO block is the permeable amorphous phase and PBT is the rigid crystalline phase, considered as impermeable for gas transport [2, 3].

This paper reports the design of a tailor made polymeric membrane by using PEO-PBT multi- block copolymers. Their properties are controlled by the fraction of PEO phase and its molecular weight, thus a structural manipulation in order to obtain a material with desired transport properties is possible. From selected PEO-PBT copolymers, blend membranes with PEG are tailored in order to design membranes with high performance for CO2 separation. One focus of this work was the development of a membrane material, which can effectively separate CO2 and H2. This is an industrially important separation, e.g. for the coal gasification process. Membranes with a preferred CO2-permeability are especially attractive, because the hydrogen remains on the high-pressure side. Blends of Polyactive® comprise 50 wt. % of PEG 200 were still mechanically stable and showed a CO2/H2- solubility selectivity of 78. This was counteracted by a CO2/H2-diffusivity selectivity of 0.17 (faster diffusion of hydrogen). The

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resulting permeability selectivity of 13 (at room temperature) is still very attractive especially when taking into account the high permeability of the hybrid material.

A study of these copolymers with different molecular weight and fraction of the PEO block have been carried out in order to develop new membrane materials for gas separation. Details on the different copolymer/PEG blends will be presented in this lecture and first machine-made membranes will be shown as well.

[1] A.A. Deschamps, D. W. Grijpma, J.Feijen, Poly (ethylene oxide)/poly(butylene terephthalate) segmented block copolymers: the effect of copolymer composition on physical properties and degradation behavior, Polymer 42 (2001) 9335- 9345.

[2] S. J. Metz, M. H. V. Mulder, M. Wessling, Gas- permeation properties of poly(ethylene oxide) poly (butylene terephthalate) block copolymers, Macromolecules 37 (2004) 4590-4597.

[3] B. Gebben, A water vapor-permeable membrane from block copolymers of poly(butylene terephthalate) and poly(ethylene oxide), J. Membr. Sci. 113 (1996) 323-329.

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Gas Separation I – 3

Monday July 14, 10:45 AM-11:15 AM, Kaua’i

Segmented Block Copolymers: A Molecular Toolbox to Tailor the Mass Transport Properties of Polymeric Nanocomposites

S. Reijerkerk (Speaker), University of Twente, The Netherlands, [email protected] A. IJzer, University of Twente, The Netherlands A. Araichimani, University of Twente, The Netherlands R. Gaymans, University of Twente, The Netherlands K. Nymeijer, University of Twente, The Netherlands M. Wessling, University of Twente, The Netherlands

The removal of CO2 from light gas mixtures such as H2, N2 and CH4 is an important application in industry, for instance in synthesis gas, flue gas and natural gas processing. Poly(ethylene oxide) (PEO) based block copolymers have been studied extensively as membrane material for these CO2/light gas separations. In general, block copolymers contain a phase separated morphology in which the hard segments (usually polyamides, polyurethanes or polyimides) provide mechanical stability and the soft segments control the gas transport properties. The polar ether oxygen linkages in PEO interact favorable with the quadrupolar CO2, resulting in high CO2/light gas solubility selectivities. Simultaneously the flexible ether oxygen linkages ensure high CO2 diffusivities and thus high CO2 permeabilities.

Incorporation of high concentrations of PEO is however difficult due to its strong tendency to crystallize, which is detrimental for the permeation properties. This is especially evident at ambient and sub ambient temperatures. Crystallization at sub ambient temperatures is especially disadvantageous for CO2/CH4 separations, as these separations often occur offshore and because higher hydrocarbons in natural gas are usually removed by condensation at low temperatures, thus reducing the need for reheating such a gas stream. Furthermore, the non-uniform nature of the hard segments usually used, leads to inefficient phase separation of the soft and hard segments, which has reduced the CO2 permeability and the mechanical strength. High hard segment concentrations (> 30 wt%) are thus required to guarantee mechanical strength, but at the same time reduce the gas permeability.

Here, we report the synthesis, characterization and gas permeation properties of a series of segmented block copolymers based on a soft segment containing a random distribution of 75 mol% PEO and 25 mol% poly(propylene oxide) (PPO) with strongly improved phase separation and a significant reduction in crystallinity of the soft segment. The crystallization of the ethylene oxide units is suppressed due to the presence of the methyl side groups of PPO, that are randomly distributed along the polymer backbone and which prevent regular

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chain packing. To ensure a well phase separated morphology a hard segment containing uniform tetra-amide units is used.

The soft segment length is varied between 1.000 - 10.000 g/mol, enabling soft phase concentrations up to 89 wt%. Crystallinity of the uniform hard segment is high (~ 80%) and the phase separation is very efficient, leading to a pure, flexible and highly permeable soft phase. Crucial in this case is the fact that PEO crystallization is absent in all materials at temperatures as low as -5°C.

Pure gas permeabilities are determined using the constant volume, variable pressure method in a temperature range from -10°C to 50°C at an upstream pressure of 4 bars. CO2 gas permeabilities at 35°C ranged from 126 Barrer (1.000 g/mol) to approximately 500 Barrer (10.000 g/mol), while gas selectivity values are as high as 10 for CO2/H2, 45 for CO2/N2 and 13 for CO2/CH4. These gas selectivities are comparable with a typical PEO containing block copolymer like PEBAX® 1074, while permeability is increased with a factor four. At a temperature of -10°C the CO2 permeability remained high with a value of 235 Barrer for a soft segment length of 10.000 g/mol. At this temperature CO2/H2, CO2/N2, and CO2/CH4 selectivities reached values of respectively 19, 99 and 31. Compared to the block copolymer systems described in literature the CO2 gas permeability is tremendously increased (> 300 Barrer increase) while the CO2/light gas selectivity is unaffected. The operating window of block copolymers for CO2 gas separation is thus expanded to the low temperature region which is interesting for CO2/CH4 as well as CO2/H2 separations.

In the present work we prove that segmented block copolymers are a successful molecular toolbox to tailor the mass transport properties of polymeric nanocomposites. A random distribution of 25 mol% PPO within a PEO oligomer suppresses PEO crystallization in PEO based segmented block copolymers. In addition, the use of a uniform hard segment results in block copolymers containing a very pure and flexible soft phase. Combined, their use enhances the CO2 gas permeability tremendously (up to a fourfold increase) over conventional PEO based block copolymers without sacrificing selectivity. To our knowledge these results are the best reported values to date for polyether based block copolymer systems.

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Gas Separation I – 4

Monday July 14, 11:15 AM-11:45 AM, Kaua’i

Gas Separation Using Ionic Liquid Polymers

R. Noble (Speaker), University of Colorado, Boulder, CO, USA, [email protected] D. Gin, University of Colorado, Boulder, CO, USA J. Bara, University of Colorado, Boulder, CO, USA T. Carlisle, University of Colorado, Boulder, CO, USA B. Voss, University of Colorado, Boulder, CO, USA A. Finotello, University of Colorado, Boulder, CO, USA

The objectives of this research are to fabricate new membrane structures based on polymerizable ionic liquids; and characterize their fundamental gas and vapor transport properties. Room temperature ionic liquids (RTILs) with polymerizable groups can be readily converted into solid-state, poly(RTILs) for use as gas separation membranes. The membranes will be fabricated from ILs (which will act as the active component to provide high selectivity for the target agents) and polymerizable ILs (which can be formed directly into solid, mechanically stable and tunable polymeric solids). The use of polymerizable lyotropic liquid crystals (LLCs) as a blendable additive to these IL materials provides a means to obtain specific nanoporous morphologies that provide the potential for enhanced sorption capacity in the resulting films or particles. LLC systems have the ability to form ordered, phase-segregated nanoporous structures and incorporate the IL into the ordered hydrophilic regions to generate very high surface area materials. Separately, the addition of inorganic NPs to IL-based sorbent systems will allow formation of solid-state materials, and provide additional surface area and adsorption capacity for the target agents. Regular solution theory has been shown to accurately predict the solubility of various gases and vapors in ionic liquids and polymers. The IL solubility parameter can be tailored to minimize the difference between the target agent and IL solubility parameters which maximizes the solubility. A functional group contribution method to determine the solubility parameter can be used to guide the detailed molecular design of the ionic liquid. This method provides a theoretical framework to interface with the material synthesis and characterization. Polymerizable ILs have already been shown to have properties that exceed the upper bound on a Robeson plot for CO2/N2 separation. The use of various additives can further enhance the permeation while maintaining the high selectivity. Results will be shown for a variety of materials.

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Gas Separation I – 5

Monday July 14, 11:45 AM-12:15 PM, Kaua’i

Development of High Temperature CO2-Selective Porous Ceramic Membranes

A. Ku (Speaker), GE Global Research, Niskayuna, NY, USA, [email protected] V. Ramaswamy, GE Global Research, Niskayuna, NY, USA J. Ruud, GE Global Research, Niskayuna, NY, USA P. Willson, GE Global Research, Niskayuna, NY, USA K. Narang, GE Global Research, Niskayuna, NY, USA

Because of their mechanical durability and thermal and chemical stability, inorganic membranes have the potential to increase the efficiency of industrial processes by enabling efficient separation of process gas streams into their constituents. Numerous industrial processes, including hydrocarbon processing, steam methane reforming, water gas shift, and CO2 capture from power generation systems, would benefit from gas separation membranes that operate at elevated temperatures. Selectivity is a key requirement for membranes. In general, porous membranes are more selective for the smaller or lighter molecules in a gas mixture. However, the mechanism of selective surface transport, due to gas adsorption on the pore walls, can increase the flux of the heavier molecule resulting in a reverse selective membrane.

Surface transport of adsorbed CO2 can lead to CO2-selectivity in porous membranes, but is believed to be a low temperature effect because of desorption of the gas upon heating. We will describe efforts to develop porous ceramic membranes with enhanced surface transport of CO2 at elevated temperatures. Based on a conceptual framework that allows screening for promising materials through chemisorption properties, we identified several promising candidate oxides and fabricated supported microporous membranes. We will report the gas permeation and separation properties of our oxide membranes against a microporous silica benchmark with substantial room temperature CO2/H2 selectivity.

Acknowledgement: This material is based partly upon work that was supported by the U.S. Department of Energy under award number DE-FC26-05NT42451.

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Gas Separation I – 6

Monday July 14, 12:15 PM-12:45 PM, Kaua’i

Solubility and Diffusivity of Organic Vapors in Mixed Matrix Membranes Formed by High Free Volume Glasses Loaded with Fumed Silica

M. Ferrari, University of Bologna, Bologna, Italy M. De Angelis, University of Bologna, Bologna, Italy M. Galizia, University of Bologna, Bologna, Italy T. Merkel, MTR- Membrane Technology and Research, Menlo Park, CA, USA G. Sarti (Speaker), University of Bologna, Bologna, Italy, [email protected]

Solubility and diffusivity of mixed matrix membranes based on amorphous Teflon® AF 2400 or PTMSP loaded with different amounts of nanoscale fumed silica (FS) have been studied at 25°C. For such systems filler addition induces variations in density as well as in sorptive capacity that do not obey an additive rule, at any filler contents. The solubility isotherms of different hydrocarbons in mixed matrices (MM) with different FS loadings up to 40 wt % are presented and discussed in some detail, together with the dependence of the apparent diffusivity on penetrant concentration and filler loading. Remarkably, with increasing the FS content the penetrant diffusivity increases as well as the apparent solubility in the polymer phase, in spite of the fact that the filler is impermeable and endowed with an adsorption capacity smaller than that of the pure polymers considered. In view of the complex behavior observed, the characterization of the permeability of the mixed matrix and its selectivity towards components in mixed gases seem to require an extensive experimental work in which use is made of different penetrants as well as of different matrices at various filler contents. Remarkably, analysis of the experimental data collected clearly indicates that the study of the mixed matrix behavior, i.e. solubility, diffusivity and permeability, can be greatly simplified and rationalized as follows: i) consider first a test penetrant and measure the solubility isotherms for the different mixed matrices at different filler contents; ii) calculate the solubility isotherms in the polymer phase alone of the MM, by considering that the adsorption contribution onto the FS surface remains the same as on the pure FS particles; iii) calculate the effective density of the polymer phase of the MM, or equivalently calculate the fractional free volume (FFV) of the polymer phase, by using the NELF model for the solubility in glassy polymers; iv) finally, use the latter value (density of the polymer phase or FFV) to calculate in a predictive way the solubility isotherms in the same MM of other penetrants of interest. The procedure indicated above has been followed in some detail, using n-butane as test penetrant; the effects of filler content on the polymer FFV and density of the different MM considered was calculated. From those values the solubility isotherms of other hydrocarbon vapors (CH4, C2, C3, and C5) and of gases (N2) were calculated from the Nelf model and the predicted values match in a rather

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satisfactory way the corresponding solubility isotherms measured experimentally. The values of the FFV thus obtained have also been used to correlate the dependence of the apparent diffusivities in the MM. In fact it was observed that the infinite dilution apparent diffusivity follows a well known exponential dependence on the FFV of the polymer matrix. In conclusion the experimental data presented indicate that it is possible to foresee the permeability of different penetrants in MM membranes based on simple analysis of a reference penetrant.

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Drinking and Wastewater Applications I – 1 – Keynote

Monday July 14, 9:30 AM-10:15 AM, Maui

Reuse/Recycle Water Opportunities and Challenges in Food/Bio Processing Industry Using Membrane Technology: Is this Myth or Reality?

H. Muralidhara (Speaker), Cargill Inc., Savage, MN, USA, [email protected]

The food processing industry uses an enormous amount of water. The water is used as a reactive ingredient during processing as a cleaning agent for heating and cooling/chilling, and for transportation. The amount of water used has been increasing for a variety of reasons during the last few years. Scarcity of quality water will be a major issue in the upcoming years.

Water availability is arguably the most pressing resource issue in the world. Fresh water is key to sustainable development. An inadequate water supply reduces opportunity for food production/processing, and also has a detrimental effect on the environment. With the advent of biofuels, the balancing act is absolutely essential. Membrane technology should be explored to mitigate this problem.

The pressure posed by lack of fresh water supplies portends rising water costs, which makes apparent the urgent need to improve water use efficiency. Recycle/reuse of water, if achieved economically, will provide greater operational flexibility and more competitive cost structure in a water-stressed world. There is indeed a dire need to address this issue.

Ninety-five percent of the U.S. fresh water is underground. North America�s largest aquifer, the Ogallala, is being depleted at a rate of 12 billion cubic meters per year. The Ogallala stretches from Texas to South Dakota and irrigates approximately one-fifth of the country’s farmland. There are also several food-manufacturing plants along the aquifer, and the water stress could have major impact on many of these operations.

This keynote will address the importance of recycle/reuse opportunities for water in the food and bio processing industries to promote sustainable development. I will focus on actual case histories to demonstrate efficiency improvements of water usage in processing, using membranes that have also had a significant impact on energy efficiency. High performing membranes with longer lifetime will expand the scope of recycling/reuse opportunities around the globe. I will conclude by discussing some of the most important future challenges and opportunities in the field on a global basis.

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Drinking and Wastewater Applications I – 2

Monday July 14, 10:15 AM-10:45 AM, Maui

Integrated Membrane System for Waste Water Reuse with Innovative PVDF UF Membrane and Low Fouling RO Membrane

T. Kitade (Speaker), TORAY Industries, Inc., Otsu, Shiga, Japan, [email protected] R. Takagi, TORAY Industries, Inc., Otsu, Shiga, Japan S. Kantani, TORAY Industries, Inc., Otsu, Shiga, Japan M. Taniguchi, TORAY Industries, Inc., Otsu, Shiga, Japan T. Uemura, TORAY Industries, Inc., Otsu, Shiga, Japan

Abstract In these years, the serious water shortage and pollution are being tangible in the world. In order to secure sustainable water resources with small environmental impact, the waste water reuse (WWR) systems have been focused, and many large-scale (WWR) plants were constructed and started operation. One of the promising WWR systems is combined with micro-filtration (MF) membrane or ultra-filtration (UF) membrane followed by the reverse osmosis (RO) process, which is called as ‘Integrated Membrane System (IMS)’. This IMS has a lot of advantage such as cost saving and high product quality, but one problem is sometimes appeared, which is the fouling of the membranes. In this study, the authors focused on the principle and the prevention of fouling, and has developed optimized IMS for WWR with high efficiency and anti-fouling operation.

1) MF/UF Fouling of MF and UF membranes at the filtration of the secondary effluent of waste water is mainly caused by the high concentration organic matters in the feed water. In order to solve this problem, we tried to utilize our innovative poly (vinylidene fluoride) (PVDF) hollow fiber MF/UF membranes. These series of membranes were developed by applying the thermally induced phase inversion technology, and had high chemical resistance and physical strength, which enabled various physical and chemical cleaning for the stable operation with wide ranges of feed water composition. At first, we have tested the permeance, permeate quality and fouling properties of three PVDF hollow fiber membranes whose structures, pore sizes and permeabilities were different, and selected one type of membranes whose name was HFU and had 150,000 dartons as the nominal molecular weight cut off size, due to the best anti-fouling property and the highest permeate water quality. Then, in order to achieve higher flux operation of the filtration process with HFU, it was tried to apply and optimize the combination of the coagulation and improved Chemical Enhanced Backwashing (CEB) technique, which was much more effective than conventional method. Firstly, the coagulation condition was focused, and then it was found out that the membrane cleaning efficiency was related to the zeta potentials of coagulated flocs and the membrane surface, and the coagulation

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condition was optimized. Secondly, the investigation was conducted for the improved Chemical Enhanced Backwashing (CEB) in order to remove more effectively the organic matters from membrane surface and inside of the micro-pores. As a result of the investigations above, the HFU filtration process achieved the extremely higher flux 167 LMH (4.0 m/d) than before (1.0~1.5 m/d), which could reduce the operational cost as well as the initial equipment cost. 2) RO The major difficulty in the RO operation for WWR is the membrane fouling due to the chemical and biological reasons. In this study, by using some organic matters measurement in order to correlate the RO feed water composition with chemical fouling property, it was found the specific organic matters were related to the chemical fouling. Based on the analyses and comparison of various RO membranes, it was confirmed that the low fouling RO membrane had the excellent performance for chemical fouling. As for the bio-fouling, the bactericides are usually used in order to prevent bio-fouling. However, it is difficult to select appropriate and effective bactericide dosing conditions. In this study, we have successfully developed the modified bio-film formation rate (BFR) technique with more accurate ATP measurement and the newly developed test column consisting of the actual RO membrane. This technique enabled to obtain the bio-fouling potentials in shorter time. By using this modified BFR technique, the bio-fouling potentials of the various RO feed water were easily measured, and the most effective bactericide dosing condition could be decided.

References

Minegishi, S., Tanaka, Y., Henmi, M., and Uemura, T., 2007, "Advanced Fouling Resistant PVDF Hollow Fiber Membrane Modules for Drinking Water Treatment ", The 2007 IWA Leading Edge Conference on Water and Wastewater Technologies, Singapore

Minegishi, S., Henmi, M., Matsuka, N., and Kurihara, M., 2003, "Newly Designed PVDF Hollow Fiber and Flat Sheet Membrane for Drinking Water Production and Wastewater Reuse ", ICOM2005, Korea

J.S. Vrouwenvelder, D. van der Kooij, 2001, "Diagnosis, prediction and prevention of biofouling of NF and RO membranes ", Desalination 139, 65- 71

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Drinking and Wastewater Applications I – 3

Monday July 14, 10:45 AM-11:15 AM, Maui

Impact of Seasonal Water Quality Changes on Low Pressure Membrane Filtration of an Activated Sludge-Lagoon Effluent.

F. Roddick (Speaker), RMIT University, Melbourne, Australia, [email protected] T. Nguyen, RMIT University, Melbourne, Australia L. Fan, RMIT University, Melbourne, Australia J. Harris, RMIT University, Melbourne, Australia

Increasing demands on Melbourne’s water resources due to population growth and drought have emphasized the need for multiple use of water, including the treatment and recycling of wastewater. Western Treatment Plant (WTP) treats approximately 52% of Melbourne’s sewage, a total of approximately 485 million liters/day, using a sequential activated sludge-lagoon (AS- lagoon) process. WTP employs two AS-lagoon systems in which sewage is treated by passing through ponds and an activated sludge plant with anoxic and aeration zones. The biologically treated effluent then passes through a clarifier and a chain of lagoons before it is transferred to the head of the road storage pond (HORS). The recycled water is currently used for various on-site and off-site purposes, however, due to catchment issues such as industrial waste input and saline aquifer infiltration, it contains salt which limits its long term use for some applications, such as agriculture, without additional management practices. Pilot-scale trials, which utilized microfiltration (MF) or ultrafiltration (UF) as a pre-treatment prior to reverse osmosis (RO), demonstrated that the product water was suitable for various applications including agriculture and domestic use.

Since the effluent from WTP contains algae and algal products from the lagoon process, as well as some residual products from the AS process, the resultant membrane fouling and permeate properties may be more problematic and differ from those arising from separate AS and lagoon processes. As the performance can vary, and the lagoons are subject to algal blooms over the warmer months, the aim of this study was to characterize the properties of the AS-lagoon effluent and to determine their influence on the performance of the MF and UF processes to determine the impact of seasonal variation. These data will be used as a basis for the development of a fouling mitigation strategy. The filterability was measured as specific permeate volume at a final flux rate of 55 L m h- 1 using a dead-end stirred cell fitted with 0.22 µm PVDF or PES (100 kDa MWCO) membranes.

The trends for a range of feed parameters over the eighteen month sampling period were established and their influence on MF and UF filterability statistically analyzed. During this period, there was a major algal bloom with consequential

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greatly elevated total suspended solids (TSS), turbidity and dissolved organic carbon (DOC). The MF and UF filterability trends were statistically analyzed including and excluding the data for this sample.

The turbidity, total algal count and TSS levels showed greater variation over October 06-March 07 (ie., the warmer months) than for the April 07-December 07 period. Some correlation between these parameters and DOC was apparent. There was a trend for lower turbidity over the April 07-August 07 period, and similarly, although to a lesser extent, for total algal count.

TDS and conductivity levels were fairly consistent over the February-December 07 period, although slightly lower levels in July-August may be indicative of a minor seasonal trend.

The MF filterability of HORS samples was generally higher for the March-December 07 period and this was reasonably consistent with their relatively low turbidity, TSS, algal contents and low DOC. TSS level was the major determinant of MF flux, MF filterability decreased to varying extents with increasing levels of these parameters in the order TSS > turbidity > total algal count > DOC whether an algal bloom was present or not.

The UF filterability of HORS samples was also generally higher for the March-December 07 period. UF filterability decreased to varying extents with increasing levels of TSS, turbidity, algal count and DOC such that the effect of DOC > TSS > turbidity > total algal count. When data pertaining to the presence of an algal bloom was included this order changed so that the effect of TSS level was greater than DOC concentration on UF flux.

Seasonal water quality changes had a greater impact on MF rather than UF filterability, which implies that UF is a better choice than MF for pre-treatment for RO in terms of consistent performance. Pre-treatment of the feed would improve water quality and thus filterability, particularly during algal bloom events, enabling more consistent membrane performance.

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Drinking and Wastewater Applications I – 4

Monday July 14, 11:15 AM-11:45 AM, Maui

Investigating and Evaluating Different Concepts of Membrane-Based Technologies for a Cleaner Production in the Automotive Industry

S. Lyko (Speaker), RWTH Aachen University, Department of Chemical Engineering, Germany, [email protected] T. Wintgens, RWTH Aachen University, Department of Chemical Engineering, Germany A. Buchmann, RWTH Aachen University, Department of Chemical Engineering, Germany T. Melin, RWTH Aachen University, Department of Chemical Engineering, Germany C. Herse, Ford-Werke GmbH, Germany

Introduction

The German automotive industry as the most stable employment sector is committed to the development and application of novel environmental technologies (VDA, 2007). The advanced treatment of its heavily concentrated wastewater streams with environmental relevance flows is nontrivial but necessary for a more frequent use of water during the production process and the minimization of wastewater discharges.

The aim of this study was to evaluate and to assess the potential of membrane processes for a modern water management in the automotive industry. By combining chemical processes (precipitation and flocculation) with porous and dense membrane processes (ultrafiltration, nanofiltration) the achievable permeate quality and the operation performance were investigated in lab and pilot scale and provided the basis for the evaluation of the recycling potential. The production site Cologne (FORD-Werke GmbH) was selected as case study as it provided a local situation with all relevant production processes of the automotive industry in use.

Methodology

The first step was a comprehensive status analysis of the local situation followed by the definition of three reliable treatment concepts covering the two fundamental strategies of production integrated (Cleaner production) and end-of-pipe technologies (EOP): Concept 1a: Production integrated measures (Cleaner production) Concept 1b: EOP treatment of the painting wastewater Concept 2: EOP treatment of the collected wastewater from the production area

To identify and evaluate the current situation the collection of existing data was enhanced by composite wastewater samples over a 24-hours period for the wastewater streams. Thereby the wastewater composition can be summarized

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by high concentrations of COD, heavy metals, oil and surfactants. Furthermore, the widespread application of biocides during various production processes resulted in unfavorable COD/BOD ratios between 7 and 10. Thus, a biological treatment was impossible and the investigated concepts were based on pressure driven membrane processes in crossflow mode.

In a comprehensive lab-scale study a coagulation agent and a membrane screening was conducted. Furthermore optimal process conditions in terms of permeate quality and filtration performance and the effect of various influencing factors (e.g. temperature, pH) were determined.

To prove these lab-scale findings and to evaluate the filtration performance and operational reliability a set of different pilot plants was installed and operated over a period of 6 months: -An ultrafiltration plant with polymeric membranes (total membrane area: 15 m²) treating the collected wastewater from the paint shop -An ultrafiltration plant with ceramic membranes (total membrane area: 7 m²) treating the collected wastewater from the mechanical production areas -A nanofiltration plant treating the process water of the phosphating department within the pre-treatment of the paint shop -A reverse osmosis plant for the advanced treatment of the nanofiltration permeate -An ultrafiltration plant treating the process water of the degreasing step within the paint shop pre-treatment -An ultrafiltration plant treating the rinsing bath water of the degreasing step within the paint shop pre-treatment

Results

The results revealed a better performance of the ceramic ultrafiltration plant in comparison to the polymeric ultrafiltration plant characterized by lower total filtration resistances and comparable retention properties. Due to the high fouling potential of the wastewater submerged hollow fibre membranes (PURON®, Koch Membrane Systems, Germany) were irreversibly blocked after the production of 2.2 m³ permeate per m² membrane area. Porous ultrafiltration membranes in combination with pre-coagulation are able to reduce the heavy metal content to a level below the environmental legislation. The molar mass distribution of the wastewater showed the largest fraction (> 90%) with a molar mass lower than 1,500 Da. This finding was proved by the incomplete COD retention of the crossflow- ultrafiltration. Therefore advanced treatment processes (powdered activated carbon, nanofiltration) to decrease the organic content as a prerequisite for the recirculation into the process were investigated and the results will be presented. The production integrated nanofiltration within the phosphating department provided a sufficient removal of heavy metals. The organic content (TOC) was identified as remarkable parameter affecting the filtration performance adversely.

Overall a broad set of data was generated and allows the presentation of a quantitative comparison of different membrane-based treatment technologies for

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an adjusted water management in the automotive industry with respect to permeate quality, process performance and economical feasibility.

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Drinking and Wastewater Applications I – 5

Monday July 14, 11:45 AM-12:15 PM, Maui

Membranes in Clean Technologies

A. Koltuniewicz (Speaker), Professor in University of Technology, Wroclaw, Poland, [email protected] E. Drioli, Professor in Istituto per la Tecnologia Delle Membrane, Italy

The clean technologies are based on effective separation of various contaminants ‘at the source’ (e.g. before any dissipation takes place) to remove, recover, reuse, or recycle them, which forms a closed cycle processes. The paper reveals the new applications of membrane processes that offer efficient, innovative pathways of reengineering and retrofitting different industrial sectors. Recovery, recycling, reuse of water and valuable components play a dominant role in saving costs resources energy, and protection of environment. The Commission of the European Communities put the definition of Clean Technologies as "any technical measures taken at various industries to reduce or even eliminate at source the production of any nuisance, pollution, or waste, and to help saving raw materials, natural resources and energy. The main attributes of Clean Technologies were precisely formulated as:

1. Conservation of raw materials 2. Optimization of production processes 3. Rational use of raw materials 4. Rational use of energy 5. Rational use of water, 6. Disposal or recycling of unavoidable waste 7. Accident prevention 8. Risk management to prevent major pollution 9. and restoring sites after cessation of activities.

Almost all attributes of the clean technologies may be fulfilled by using membrane processes.

Conservation and rational use of raw materials is possible by application of membrane processes for recovery, reuse, and recycling of unreacted substrates, water and production media such as catalysts, solvents, surfactants, adsorbents, cooling agents etc. Diluted metal ions may be gained from waste streams, mining waters, tailings, leachates, seawaters etc. Diluted organic compounds may be concentrated during pervaporation or membrane distillation, which additionally takes advantage of and utilizes a waste heat. Thus membrane processes open a new unexploited source of raw materials.

Membranes play an important role in optimization of production process and rational use of energy in many ways, e.g. by the substitution of less energy consuming membrane alternatives or their combination with conventional unit processes which are known as ‘hybrid processes’. Membranes also open a new

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prospect for new energy sources as fuel cells, new fuels. Conventional Energetic sector uses large scale membrane plants for water recycling. Oil, gas and petrochemical industries use membrane processes for products fractionation and purification. Membranes may contribute in huge energy savings thanking to new solutions of work, pressure, and energy recovery systems.

Water scarcity on the Earth is less harmful thanks to the exploitation of new water resources. Desalination of brackish waters, sea waters and mining waters by means of reverse osmosis and nanofiltration is matured practice. A rational use of water during industrial processes may be attained by means of multiple use and appropriate management of water and wastewater streams. In these cases the proper adjusting of water quality to particular needs of each consumer (within one water network) may be attained by membrane application for the removal of all types of contaminants, e.g.: suspended solids, colloids, soluble components, ions organic components. The disposal or recycling of unavoidable waste streams may be achieved by a variety of membrane separations, which enable to fractionate the wastewaters onto valuable pure materials that can be subsequently reused as a resources or valuable by-products. The water recovered by such separation can be recycled to the production processes.

Membrane processes reduce chemicals consumption during the regeneration of ion exchange resins during water softening in power stations, and other pollutants. Membranes enable the avoidance of the overdosing of fertilizers and all kinds of chemicals used in agriculture, such as herbicides, and pesticides, by means of controlled release. Insecticides are replaced by pheromones that are also delivered precisely by means of membranes.

The aim of the paper is to:

1. Deliver up-to-date information about successful applications of membrane based clean technologies in variety of industrial sectors, which may be a pattern and stimulus for further development.

2. Present methodology of membrane implementation in clean technologies by comparison of different alternative solutions and factors for evaluating their effectiveness

3. Anticipate new potential area of membrane applications in clean technologies basing on actual achievements and trends in development of membrane processes.

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Drinking and Wastewater Applications I – 6

Monday July 14, 12:15 PM-12:45 PM, Maui

Oxygen and Carbon Dioxide Control by Membrane Contactors in Desalination

A. Criscuoli (Speaker), Institute on Membrane Technology, ITM-CNR, Italy, [email protected] M. Carnevale, Institute on Membrane Technology, ITM-CNR, Italy H. Mahmoudi, Sciences & Engineering Sciences Faculty,University of Chlef, Algeria S. Gaeta, GVS S.P.A., Italy F. Lentini, GVS S.P.A., Italy S. Reggiani, GVS S.P.A., Italy E. Drioli, Department of Chemical Engineering and Materials, University of Calabria, Italy

In a desalination plant the content of oxygen and carbon dioxide has to be controlled because it is responsible of corrosion problems in pipelines and of the pH and the conductivity of the water. Moreover, the pH of the water can influence the precipitation and scaling phenomena, so an adequate control becomes essential for reducing fouling issues inside the plant. Chemical agents are often used for adjusting the pH while vacuum/stripping towers have traditionally been used to remove dissolved gasses. More recently, membrane contactors have been proposed as alternative systems for water deoxygenation (particularly for the semiconductor industry and boilers). The aim of this work is to apply membrane contactors for the oxygen removal, as well as the pH control in a desalination plant. Experimental tests have been carried out in a lab set-up with a flat membrane module of 40 cm2 of membrane area, by feeding in a counter-current mode the liquid stream and a gas stream (consisting of CO2 or N2). The liquid stream was recycled to the module while the gas stream was sent in continuous. Different parameters have been varied, such as the temperature, the streams flow rates, the liquid composition. In particular, the liquid streams sent to the system were distilled water and synthetic solutions, prepared for simulating the reverse osmosis permeate and brine and the nanofiltration permeate. In this way, the performance of the membrane contactor in different parts of a desalination plant has been studied in terms of oxygen removal and pH variations. Five different flat hydrophobic membranes of 0.2 mm were tested and compared: PVDF, PVDF-treated, acrylic-based, PTFE and PP membranes. Before tests, all membranes have been characterized by swelling, CAM and SEM analysis. The oxygen removals were higher at higher temperatures and higher liquid flow rates, varying slightly with the gas flow rates. Higher removals were achieved for the more concentrated streams, due to the ‘salting-out effect’. Both CO2 and N2 gas streams were able to strip, in a similar extent, the dissolved oxygen from the liquid solutions. However, the final pH of the water decreased after the tests with CO2, whereas increasing or remaining constant after using N2, depending on the solution treated. This result is of extreme interest, because, depending on the specific needs, it will be possible to couple the

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oxygen removal to the desired pH. Concerning the performance of membranes, the highest oxygen removal from distilled water has been obtained with the PTFE membrane; however, during tests with saline solutions the removal decreased, probably due to a reduction of the open structure, as observed by SEM.

Acknowledgements The authors acknowledge the financial support of the European Commission within the 6th Framework Program for the grant to the Membrane-Based Desalination: An Integrated Approach project (acronym MEDINA). Project no.: 036997.

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Polymeric Membranes I – 1 – Keynote

Monday July 14, 9:30 AM-10:15 AM, Moloka’i

Layer-by-Layer Assembly in Membrane Pores for Ion Separations and Biocatalysis

D. Bhattacharyya (Speaker), University of Kentucky, Lexington, KY, USA, [email protected] A. Hollman, University of Kentucky, Lexington, KY, USA A. Butterfield, University of Kentucky, Lexington, KY, USA V. Smuleac, University of Kentucky, Lexington, KY, USA S. Datta, University of Kentucky, Lexington, KY, USA

The development of new-generation materials that extend the industrial applications of membrane processes will require a high level of control of both the characteristics of the base polymeric or inorganic support layer, as well as, its corresponding surface properties. Current research in membrane science is now focusing more on the modification of surface physical along with chemical properties using techniques like plasma or radiation-induced polymer grafting, immobilization of reactive ligands, layer-by-layer assembly, etc. Membranes functionalized with appropriate macromolecules can indeed provide applications ranging from tunable flux and separations, toxic metal capture, to nanoparticle synthesis for toxic organic dechlorination. Microfiltration membranes (eg, cellulosics, silica, polysulfone, polycarbonate, PVDF) can be functionalized with a variety of reagents. Depending on the types of functionalized groups (such as, chain length, charge of groups, biomolecule, etc.) and number of layers, these microfiltration membranes could be used in applications ranging from metal (or oxyanions) separation to biocatalysis. The dependence of conformation properties of polyelectrolytes on pH also provides tunable separation and flux control.

Layer-by-layer (LBL) assembly technique, most commonly conducted by intercalation of positive and negative polyelectrolytes or polypeptides, is a powerful, versatile and simple method for assembling supramolecular structures . Non-stoichiometric immobilization of charged polyelectrolyte assemblies within confined pore geometries leads to an enhanced volume density of ionizable groups in the membrane phase. This increase in the effective charge density allows for Donnan or charge-based exclusion of ionic species using porous materials characterized by hydraulic permeability values well beyond conventional membrane processes. Multilayer assemblies were fabricated using both PLGA (poly-L-glutamic acid)/PLL(poly-L-Lysine) and synthetic polyelectrolytes (poly(styrene sulfonate)/poly(allylamine)) in an attempt to compare the level of adsorption and separation properties of the resulting materials. The role of salt concentration in the carrier solvent on overall polyelectrolyte adsorption was examined to determine its effect on both solute

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(Cl-, SO42-, As(V)) and water transport. This type of assembly has shown that >

95% arsenic can be removed from water even at 1-3 bar operations. Constriction of the pore size induced by multilayer propagation was monitored through permeability measurements and dextran rejection studies at each stage of the deposition process.

Multilayer assemblies of polyelectrolytes can also be created within the membrane pore domain for enzyme immobilization and catalysis. Functionalized membranes were created by two different approaches. In the first approach, alternative attachment of cationic and anionic polyelectrolytes was carried out using LBL assembly technique within nylon based microfiltration (MF) membrane. In the second approach, hydrophobic poly-vinylidene fluoride (PVDF) MF membrane was functionalized by in-situ polymerization of acrylic acid. The enzyme, glucose oxidase (GOX), was then electrostatically immobilized inside the functionalized membrane domains to study the catalytic oxidation of glucose to gluconic acid and H2O2. Characterization of the functionalized membranes, in terms of polyelctrolyte / polymer domains and permeate flux was also studied. Kinetics of H2O2 formation are studied, along with the effects of residence time and pH on the activity of GOX. Stability and reusability of the electrostatically immobilized enzymatic system were also established. Applications also include other bio-catalytic reaction systems. This research is supported by the NIEHS-SBRP program

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Polymeric Membranes I – 2

Monday July 14, 10:15 AM-10:45 AM, Moloka’i

Unusual Temperature Dependence of Positron Lifetime in a Polymer of Intrinsic Microporosity

K. Rätzke (Speaker), Technische Fakultät der CAU, Lehrstuhl für Materialverbunde, Kaiserstr. 2, Germany, [email protected] R. Lima De Miranda, Technische Fakultät der CAU, Lehrstuhl für Materialverbunde, Kaiserstr. 2, Germany J. Kruse, Technische Fakultät der CAU, Lehrstuhl für Materialverbunde, Kaiserstr. 2, Germany F. Faupel, Technische Fakultät der CAU, Lehrstuhl für Materialverbunde, Kaiserstr. 2, Germany D. Fritsch, Institut für Polymerforschung, GKSS-Forschungszentrum Geesthacht, Germany V. Abetz, Institut für Polymerforschung, GKSS-Forschungszentrum Geesthacht, Germany P. Budd, School of Chemistry, The University of Manchester, Manchester, UK J. Selbie, School of Chemistry, The University of Manchester, Manchester, UK N. McKeown, School of Chemistry, Cardiff University, Cardiff, UK B. Ghanem, School of Chemistry, Cardiff University, Cardiff, UK

The performance of glassy polymeric membranes for gas separation is mainly determined by the availiability of free volume. Polymers of intrinsic microporosity are interesting candidates due to the high abundance of accessible free volume.

Positron annihilation lifetime spectroscopy (PALS) is a generally accepted method for investigation of free volume in polymers due to the so-called standard model developed by Tao and Eldrup. This simple quantum mechanical model assumes the Ps to be confined to spherical holes with infinitely high walls and gives a direct relationship between pick-off lifetime of orthopositronium and the size of the free volume holes. Since hole sizes in amorphous polymers are relatively broadly distributed, the discrete o-Ps lifetime obtained from fits to lifetime spectra and hence the hole radius has to be regarded as an average value.

We performed measurements of the temperature dependence of PALS in two polymers of intrinsic microporosity (PIM-1 and PIM-7) in the range from 143 to 523 K[1]. The mean value of the free volume calculated from the ortho-positronium life time is in the range of typical values for high free volume polymers. However, the temperature dependence of the local free volume is non-monotonous in contrast to the macroscopic thermal expansion. The tentative explanation is linked to the spirocenters in the polymer. The intensity shows no anomalous temperature behavior, but is dependent on the pretreatment of the samples. Experiments are underway to clarify this unusual behavior and will be presented on the conference.

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[1] R. Lima de Miranda, J. Kruse, K. Rätzke, D. Fritsch, V. Abetz, P. M. Budd, J. D. Selbie, N. B. McKeown, B. S. Ghanem and F. Faupel, pss-rapid research letters, phys. stat. sol. (RRL) 1, No. 5, 190-192 (2007)

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Polymeric Membranes I – 3

Monday July 14, 10:45 AM-11:15 AM, Moloka’i

Macrovoid Formation in Polymeric Membranes and Critical Factors in Fabricating Macrovoid-free Hollow Fiber Membranes

N. Peng, Department of Chemical & Biomolecular Engineering, National University of Singapore, Singapore T. Chung (Speaker), Department of Chemical & Biomolecular Engineering, National University of Singapore, Singapore, [email protected] K. Wang, Department of Chemical & Biomolecular Engineering, National University of Singapore, Singapore

The origins of macrovoids and the ways to eliminate them have received great attention and heavy debates during the last five decades, but no convincing and agreeable comprehension has been achieved. Recently, due to resource depletion, record high oil prices, and clean water shortage, the development of macrovoid-free hollow fibers for water production and recycle, energy and medical applications has received tremendous attention worldwide in the membrane companies. This work will systematically investigate the key factors to form macrovoid-free hollow fiber membranes. We have observed there should be critical values of polymer concentration, air gap distance and take-up speed, only above all of which the macrovoid-free hollow fibers can be successfully produced. This observation was confirmed for hollow fibers spun from different polymer materials such as polysulfone, P84 and cellulose acetate, and may be even universally applicable for other polymers. The major mechanisms why these critical parameters can effectively suppress macrovoids will be elaborated. The most important of all, the concept of acceleration of stretch has been proposed to quantitatively correlate the critical polymer concentration, critical take-up speed and critical air gap distance in the formation of macrovoid-free hollow fiber membranes for a polymer/solvent binary system. A linear relationship can be reasonably observed between the square root of the number of macrovoids per unit area and the acceleration of stretch. Even though this mathematical description is still in its early stage and requires further investigation due to the complexity of spinning process, this model does provide some fundamental understanding of material related and process related tendency of macrovoid formation, as well as implies there may be a universal scaling to characterize a two- component polymer solution to fabricate macrovoid-free hollow fiber membranes in consideration of extension viscosity, Weissenberg number and die swell phenomena.

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Polymeric Membranes I – 4

Monday July 14, 11:15 AM-11:45 AM, Moloka’i

Preparation of Porous Poly (ether ether ketone) Membranes

Y. Ding (Speaker), PoroGen Corporation, Woburn, MA, USA, [email protected] B. Bikson, PoroGen Corporation, Woburn, MA, USA

Membrane separation processes can be energy efficient as compared to distillation since components do not undergo phase change during separation. In order to replace the energy intensive distillation and evaporation separation technologies utilized by numerous industries, including the energy sector and the pharmaceutical industry, with a membrane process, a membrane system that is capable of operation in the presence of various organics and at elevated temperatures is required. Most conventional commercially available polymeric membranes are prepared by solution based processes and thus do not provide the desired solvent and/or chemical resistance. Inorganic membranes can operate in a broad range of organic solvents and at elevated temperatures but typically do not have sufficient hydrolytic stability and can be cost prohibitive. Poly(ether ether ketone), PEEK, is a semi-crystalline high performance engineering polymer, that is well known for its solvent/ chemical resistance and a high temperature operating capability. The excellent chemical and physical characteristics of PEEK make it an ideal candidate for the preparation of the next generation of polymeric membranes that can combine inorganic membrane performance capability with polymeric membrane price. Herein, we report successful preparation of porous PEEK membranes and their applications for fluid separation at high temperatures and in organic solvent media.

Porous PEEK membranes were prepared by a melt extrusion process from compatible PEEK/polyimide blends. The polyimide served as a porogen and was removed quantitatively to form the target porous PEEK membrane. Membrane morphology and pore size was controlled by the blend composition and processing conditions. The methodology is highly flexible and provides for preparation of both flat sheet and hollow fiber membranes. PEEK exhibits thermo-mechanical properties superior to almost all engineering polymers currently in use in membrane preparation. Porous PEEK membranes are semi-crystalline with the crystalline fraction typically higher than 35%. This degree of crystallinity is comparable to that of dense (non- porous) PEEK articles produced by melt extrusion. Consequently, porous PEEK membranes are highly solvent resistant and can operate at high temperatures. These characteristics enable the use of PEEK membranes in aggressive fluid environments and at high operating temperatures. These characteristics also enable preparation of PEEK membranes with modified surface characteristics by functionalizing the surface without altering membrane morphology or durability.

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Porous PEEK membranes with controlled pore size in the range of 5 to 500 nm were prepared. The methodology allows for preparation of porous materials with a high pore volume and very high surface area. Porous membranes with a surface area as high as 250 m2/g were prepared as measured by nitrogen adsorption BET.

Hollow fiber membranes with broad range of dimensions ranging from 250 nm to 2 mm in diameter were prepared and showed stable filtration performance in a broad range of solvents including chlorinated hydrocarbons, aprotic solvents, aromatic solvents, alcohols and ketones.

Surface functionalization was utilized to further tailor membrane characteristics towards target separation application. Hydrophilic PEEK membranes were prepared by modifying porous PEEK membrane surface with hydroxyl groups (~OH) through selective ketone group reduction or by grafting hydroxyl group containing molecules to porous PEEK membrane surface through imine group formation. This methodology allows for preparation of hydrophilic membranes with the surface energy as high as 65 dyne/cm. Highly hydrophobic porous membranes are prepared by grafting porous PEEK membrane surface with perfluorohydrocarbons. Porous membranes with very low surface energy that do not wet by alcohols can be prepared.

Porous PEEK hollow fibers can serve as an ideal substrate for preparation of composite membranes. Nanofiltration membranes and gas separation membranes can be prepared by depositing a surface separation layer by solution coating or by surface grafting. PEEK based nanofiltration membranes with molecular weight cut-off of 2000 Dalton capable of stable operation in solvents was prepared. Composite gas separation membranes capable of high temperature operation were also prepared. Stable continuous operation in air for more than 500 hours at 200 ºC was demonstrated.

Acknowledgements: The work was supported in part by DOE Invention and Innovation Program, DOE SBIR Program and USDA SBIR program.

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Polymeric Membranes I – 5

Monday July 14, 11:45 AM-12:15 PM, Moloka’i

Design of New Membranes Assisted By Block Copolymer Assembly

S. Querelle, Université Montpellier, France F. Ellouze, Ecole Nationale d'Ingénieur de Tunis, France D. Quémener, Université Montpellier, France A. Deratani (Speaker), Université Montpellier, France, [email protected] T. Phan, University Aix-Marseille, France D. Gigmes, University Aix-Marseille, France D. Bertin, University Aix-Marseille, France

Block copolymers enable well-defined micro- and nano-structure design thanks to their excellent properties to self-assemble. This building bricks can be used in Membrane Science in order to control membrane morphology. It is assumed that heterogeneous structure (high polydispersity of the pore size) could be reorganized in homogeneous structure by using block copolymers. In this contribution, our last results in this field will be discussed, showing that block copolymers, pure or in blend, can help in the production of membrane with controlled architecture and interfacial properties.

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Polymeric Membranes I – 6

Monday July 14, 12:15 PM-12:45 PM, Moloka’i

Effect of Network Structure Modifications of Cross-linked Poly(ethylene oxide) Membranes on Gas Separation Properties

V. Kusuma (Speaker), University of Texas at Austin, Austin, TX, USA, [email protected] B. Freeman, University of Texas at Austin, Austin, TX, USA M. Danquah, University of Kentucky, Lexington, KY, USA M. Borns, University of Kentucky, Lexington, KY, USA A. Comer, University of Kentucky, Lexington, KY, USA D. Kalika, University of Kentucky, Lexington, KY, USA

Cross-linked poly(ethylene oxide) (XLPEO) was recently identified as a promising material to remove polar and acid gases, such as CO2, from mixtures with light gases[1]. Prepared by cross-linking low molecular weight poly(ethylene glycol) diacrylate with other poly(ethylene oxide) acrylates, XLPEO exhibits good separations properties thanks to the ethylene oxide group interaction with CO2 and elimination of crystallinity due to the presence of cross-links.

This talk will discuss recent efforts aimed at exploring other cross-linkable poly(ethylene oxide) containing acrylates to improve separations performance of XLPEO. In particular, we will explore the effects of copolymerizing poly(ethylene glycol) diacrylate with monoacrylates with a variety of functional groups. This modification results in substantial changes in polymer free volume and chain mobility, which, in turn, affects the transport properties of the materials. Dynamic mechanical analysis results will be presented along with transport properties measurement results to correlate the changes in network structure with the changes in transport properties.

[1] H. Lin, T. Kai, B. D. Freeman, S. Kalakkunnath, D. S. Kalika, The Effect of Crosslinking on Gas Permeability in Crosslinked Poly(ethylene glycol diacrylate), Macromolecules 2005, 38, 8381-8393.

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Biomedical and Biotechnology I – 1 – Keynote

Monday July 14, 9:30 AM-10:15 AM, Honolulu/Kahuku

Fouling Characteristics of Virus Filtration Membranes

M. Bakhshayeshi, The Pennsylvania State University, University Park, PA, USA R. Kuriyel, PALL Life Sciences, USA N. Jackson, PALL Life Sciences, USA A. Mehta, Genentech, USA O. Paley, Genentech, USA A. Zydney (Presenting), The Pennsylvania State University, University Park, PA, USA, [email protected]

Virus filtration provides a robust, size-based method for virus removal that compliments other unit operations to achieve the very high levels of viral clearance required for the production of therapeutic proteins. Several manufacturers make membranes specifically targeted for virus filtration applications, each having very different pore morphologies. A critical challenge for all virus filtration membranes is protein fouling, which can severely limit the membrane capacity and may even contribute to incomplete virus retention. The objective of this study was to examine the fundamental mechanisms governing protein transport and fouling during virus filtration.

Experiments were performed with Pall Ultipor DV20 virus filters made from a hydrophilic PVDF membrane, with Bovine Serum Albumin and Human Immunoglobulin G used as model proteins. Data were obtained for operation at both constant pressure and constant flux, with the protein size distribution analyzed using high performance size exclusion chromatography. Results for the flux decline (for operation at constant pressure) and pressure rise (for operation at constant flux) were analyzed using available fouling models. The effects of fouling on the membrane were examined from both buffer permeability and dextran sieving measurements obtained with the clean and fouled membranes.

Protein recovery was essentially 100% under all conditions, with no measurable retention of protein monomers or dimers. Stirring had almost no affect on the flux (at constant pressure) or the transmembrane pressure (at constant flux), indicating that concentration polarization effects were negligible in this system. The rate of fouling for the DV20 filters was quite low compared to prior results obtained with Viresolve membranes, which appears to be due to differences in the membrane permeability and underlying pore structure. Fouling caused a small shift in the dextran sieving profiles, consistent with a reduction in the effective membrane pore size. The membrane capacity appears to be a complex function of the bulk protein concentration, with the capacity passing through a maximum at an intermediate protein concentration under some conditions. These

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results provide important insights into the design and operation of virus filtration systems for the production of therapeutic proteins.

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Biomedical and Biotechnology I – 2

Monday July 14, 10:15 AM-10:45 AM, Honolulu/Kahuku

Developments in Membrane Affinity Chromatography for Monoclonal Antibody Recovery

S. Dimartino, University of Bologna, Bologna, Italy C. Boi, University of Bologna, Bologna, Italy G. Sarti (Speaker), University of Bologna, Bologna, Italy, [email protected]

The great number of process development for monoclonal antibodies, presently in development stage, has emphasized the capability limits of the biotech industry. The recent improvements of cultivation technology, allow also to achieve high titers of monoclonal antibody in cell supernatants, and the present bottleneck for MABs’s production is associated to the downstream process required for product recovery. Bead-based affinity chromatography with Protein A is widely used in the primary capture stage. Membrane affinity chromatography has not yet experienced extensive application due to the lower capacity of membrane supports compared to chromatographic beads, yet it has several advantages deserving serious attention. This work is focused on the purification of Immunoglobulin G (IgG) with affinity membranes. A new Protein A affinity membrane (Sartorius, Göettingen, Germany), as well as affinity membranes prepared with synthetic ligands have been characterized in detail in batch and dynamic experiments. The membranes have been analysed by using pure solutions of polyclonal IgG, to determine their binding capacity, as well as a cell supernatant containing monoclonal IgG, to investigate their selectivity and general behavior. The influence of process conditions like flow rate and feed concentration on adsorption and elution have been studied to obtain indications for the optimal process conditions. The affinity membrane purification process was also simulated with a mathematical model which was validated by using the experimental data obtained. The model can simulate adsorption, washing and elution steps by taking into account all the relevant transport phenomena.

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Biomedical and Biotechnology I – 3

Monday July 14, 10:45 AM-11:15 AM, Honolulu/Kahuku

Bioactive Membranes for Liver Tissue Engineering

L. De Bartolo (Speaker), Institute on Membrane Technology, National Research Council of Italy, ITM-C, Italy, [email protected] S. Salerno, Institute on Membrane Technology, National Research Council of Italy, ITM-C, Italy A. Piscioneri, Institute on Membrane Technology, National Research Council of Italy, ITM-C, Italy S. Morelli, Institute on Membrane Technology, National Research Council of Italy, ITM-C, Italy M. Rende, Institute on Membrane Technology, National Research Council of Italy, ITM-C, Italy C. Campana, Institute on Membrane Technology, National Research Council of Italy, ITM-C, Italy E. Drioli, Institute on Membrane Technology, National Research Council of Italy, ITM-C, Italy

Biomaterials in tissue engineering and regenerative medicine should provide the necessary support for cells to proliferate and maintain their differentiated functions. The use of polymeric semipermeable membranes with different physico-chemical and transport properties is appealing in tissue engineering and bioartificial organs since these and biomembranes share similarities such as the selective transport of molecules, resistances and protection. Furthermore, synthetic membranes can easily be mass produced modulating their morphological and physico-chemical properties for specific applications. Semipermeable membranes for their characteristics of selectivity, stability and biocompatibility could provide a support for the maintenance of hepatocyte phenotype and differentiated functions. In this study we report on the synthesis of novel semipermeable membranes able to support the long-term maintenance and differentiation of human liver cells and on the strategies to optimise cell-biomaterial interactions in biohybrid systems. We developed membrane biohybrid system constituted by membranes made from a polymeric blend of modified polyetheretherketone and polyurethane (PEEK-WC-PU) and human hepatocytes. This membrane combines the advantageous properties of the polymers (i.e., biocompatibility, biostability and biofunctionalities) with those of membranes such as permeability, selectivity and well-defined geometry. Molecular modifications of the membrane elicit specific interactions with cell receptors and thereby enhance liver functions. Human hepatocytes organize in a 3D structure in the membrane biohybrid system maintaining a polygonal shape, which would lead to better functional maintenance, so many of the features of the liver in vivo are reconstituted. Liver specific functions investigated in terms of urea synthesis, albumin production and total protein secretion are maintained at high levels. Hepatocytes are able to biotransform diazepam, which is an anti anxiety agent (benzodiazepines), through the formation of its typical metabolites including temazepam, N-desmethyl-diazepam and oxazepam. This engineered liver construct is able to promote adhesion and to provide a microenvironment able to elicit specific cellular responses.

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Acknowledgments The Authors acknowledge European Commission through the Livebiomat project, Contract No. NMP3-CT-2005-013653.

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Biomedical and Biotechnology I – 4

Monday July 14, 11:15 AM-11:45 AM, Honolulu/Kahuku

Separation and Purification of Hematopoietic Stem Cells from Human Blood through Surface-modified Membranes

A. Higuchi (Speaker), Nat. Central Univ. & Nat. Res. Institute for Child Health & Develop., Tokyo, Japan, [email protected] Y. Chang, Chung Yuan Christian University, Taoyuan, Taiwan R. Ruaan, National Central University, Taoyuan, Taiwan W. Chen, National Central University, Taoyuan, Taiwan

Efficient cell separation is important for the successful isolation and purification of blood cells, stem cells and specific tissue cells. Techniques such as centrifugation, affinity column chromatography, and fluorescence activated cell sorting (FACS), magnetic cell selection, and membrane filtration are typically employed for cell separation. The centrifugal separation of cells is a typical method employed to isolate platelets, leukocytes, mononuclear cells, red blood cells and non-blood cells. Highly purified cellular preparations are obtained using FACS or a magnetic cell selection system in conjunction with a fluorescently-labeled antibody as the cell-surface marker. Cell separation through membrane filtration was recently reported by several researchers. Leukocyte removal filters are commercially available cell separation filters. The stem cells that form blood and immune cells are known as hematopoietic stem cells. Hematopoietic stem and progenitor cells bear the CD34 cell surface marker. These cells are thought to be responsible for the reconstitution of hematopoiesis. Therefore, the transplantation of CD34+ cells is essential in the therapy of patients with acute myeloid leukemia, myelodysplastic syndromes, chronic myeloid leukemia and systemic mastocytosis. In a previous investigation (A. Higuchi et al., J. Biomed. Mater. Res. 68A, 34 (2004)), cell separation from peripheral blood at fixed blood permeation speeds (1 ml/min) was investigated using surface-modified polyurethane (PU) membranes with a fixed pore size of 5 mm, carrying different functional groups. However, optimal conditions for the purification of CD34+ cells from blood using membrane filtration were still undetermined. In this study, we prepared several of the membranes, and conducted further experiments on the separation of CD34+ cells using the membranes.

Cell separation from peripheral blood was investigated using polyurethane (PU) foam membranes having 5.2 mm pore size and coated with Pluronic F127 or hyaluronic acid. The permeation ratio of hematopoietic stem cells (CD34+ cells) and lymphocytes through the membranes was lower than for red blood cells and platelets. Adhered cells were detached from membrane surfaces using human serum albumin solution after permeation of blood through the membranes, allowing isolation of CD34+ cells in the permeate (recovery) solution. High- yield

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isolation of CD34+ cells was achieved using Pluronic-coated membranes. This was because the Pluronic coating dissolved into the recovery solution at 4oC, releasing adhered cells from the surfaces of the membranes during permeation of human serum albumin solution through these membranes. Dextran and/or bovine serum albumin solutions were also evaluated for use as recovery solutions after blood permeation. A high recovery ratio of CD34+ cells was achieved at 4oC in a process using 20% dextran solution through polyurethane (PU) membranes having carboxylic acid groups. CD34+ (hematopoietic stem) cells were efficiently recovered (85% recovery ratio) through PU-COOH membranes in a process using 20 wt% aqueous dextran as the recovery solution. This indicated that dextran solution was preferable to HSA and BSA solutions during the recovery process.

Forraz et al. (Stem Cells 22, 100 (2004)) reported that negative-isolated cells, which depleted umbilical cord blood mononuclear cells from blood cells expressing mature hematopoietic markers (glycophorin A, CD2, CD3, CD7, CD16, CD33, CD38, CD45 and CD56), lineage- negative cells, enriched long-term culture- initiating cells. The lineage-negative cells maintained and expanded more primitive hematopoietic stem and progenitor cells than CD34+ and CD133+ cells, and expressed higher levels of the cell-adhesion molecule CD162 [expression ratio (ER) = 16.0%] and CD164 (ER = 96.7%) involved in hematopoietic progenitors forming bone marrow than CD34 (ER = 14.4%) and CD133 (ER = 7.0%). Therefore, primitive hematopoietic stem and progenitor cells tend to adhere to polyurethane (PU) membrane surfaces, due to their expression of these cell-adhesion molecules on their surfaces.

The exact surface marker for primitive hematopoietic stem and progenitor cells remains unclear at the current time. Isolating such cells by membrane filtration of umbilical cord or bone marrow is thought to be more effective than magnetic bead or flow cytometry sorting methods, because cell separation in membrane filtration is based not only on cell size, but also on the intensity of cell adhesion to the membrane surface. Of all methods, membrane separation is likely to provide the most sanitary and simple isolation of primitive hematopoietic stem and progenitor cells.

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Biomedical and Biotechnology I – 5

Monday July 14, 11:45 AM-12:15 PM, Honolulu/Kahuku

Membrane Chromatography: Protein Purification using Newly Developed, High-Capacity Adsorptive Membranes

B. Bhut (Speaker), Clemson University, Clemson, SC, USA, [email protected] S. Wickramasinghe, Colorado State University, Fort Collins, CO, USA S. Husson, Clemson University, Clemson, SC, USA

Considering that the total cost of protein therapeutics is shifting from cell culture to downstream purification, high productivity and high resolution separation techniques are in demand by the biopharmaceutical industry. Membrane chromatography offers several advantages over resin-based media, such as low pressure drop and facile scale up and set up. High dynamic capacities are needed to meet productivity demands. The objective of this research was to investigate dynamic adsorption capacities and protein fractionation behavior of newly developed adsorptive membranes. High dynamic capacity (>50 mg/ml BSA) ion-exchange membranes were produced by grafting functional polymer nanolayers from commercially available regenerated cellulose membranes using atom transfer radical polymerization. Separation parameters and dynamic adsorption capacities were measured using polymerization time as independent variable. Flow effects on dynamic binding capacity and separation efficiency were studied using an Akta purifier.

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Biomedical and Biotechnology I – 6

Monday July 14, 12:15 PM-12:45 PM, Honolulu/Kahuku

Using Micro-Dialysis to Monitor Tissue Production

J. Wu (Speaker), University of Durham, Durham, UK, [email protected] R. Field, University of Oxford, Oxford, UK

Diseased or damaged tissues as well as tissue degeneration are common to all living organisms. Tissue engineering has the potential to address tissue failure by providing functional biological substitutes grown in vitro that are able to integrate with host tissues and remodel in vivo after implantation. There is a growing interest in using large pore size probes for microdialysis of macromolecular markers to monitor cell and tissue functions, and to determine the optimal conditions for the design and manufacture of scalable bioprocessing system for the regeneration of three-dimensional tissue that behaves similarly to their biological counterparts.

Fluid balance could be an important issue when using such probes and Li et al (JMS 2008) studied three modes of operation. The pumping systems generated either push or pull or push-and-pull modes of flow. It was found that the relative recovery of small solutes is not affected much by the applied pumping method but that the relative recovery of macromolecules is significantly influenced.

Through use of the Krogh cylinder assumption analytical expressions are obtained which contribute towards an explanation of this finding. Also a comparison is made between the concentration distribution of tracers that are added to the nutrient feed and the concentration distribution of produced material. There can be a significant difference between the two depending upon the selectivity of the microdialysis probe.

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Membrane Fouling - General Topics – 1 – Keynote

Monday July 14, 9:30 AM-10:15 AM, O’ahu

Protein Fouling of Polymeric Membranes: Modeling and Experimental Studies Using Ultrasonic Frequency-Domain Reflectometry

E. Kujundzic, University of Colorado at Boulder Department of Mechanical Engineering, Boulder, CO, USA K. Cobry, University of Colorado at Boulder Department of Mechanical Engineering, Boulder, CO, USA C. Ho, University of Cincinnati, Department of Chemical and Materials Engineering, Cincinnati, OH, USA W. Li, University of Cincinnati, Department of Chemical and Materials Engineering, Cincinnati, OH, USA A. Greenberg, University of Colorado at Boulder Department of Mechanical Engineering, Boulder, CO, USA M. Hernandez (Speaker), University of Colorado at Boulder Department of Civil, Architectural and Engineering, Boulder, CO, USA, [email protected]

Biofouling is a major problem associated with membrane separation processes that causes decreased performance and altered selectivity. Biofouling typically occurs either on the membrane/feed solution (external) surface or within the pores that are internal to the membrane structure. Accurate characterization of protein fouling as it occurs is crucial for an improved understanding of fouling mechanisms with respect to biofouling control and membrane cleaning optimization. A promising approach for achieving these objectives involves the application of fouling models, which can be validated using data from non-invasive, real-time monitoring of relevant membrane separations. Clearly, there are significant benefits in employing real-time, non- destructive methods that can resolve changes in accumulating mass on membrane surfaces and/or to the materials that fill membrane pores, where these markedly different fouling mechanisms can be isolated from each other. The only practical methodology that currently satisfies these criteria is ultrasonic reflectometry (UR). Recent reports have described the ability of UR to monitor the development of biofilms on the surfaces of flat- sheet and hollow-fiber membranes used for drinking water treatment. We describe the use of novel signal-processing protocols to extend the sensitivity of UR for real-time in-situ monitoring of MF membrane fouling during protein separations and purification.

Different commercial MF membranes with a nominal pore size of 0.2µm were challenged using bovine serum albumin (BSA) and well-characterized bacterial amylase as model proteins. Biofouling induced by these proteins was observed in flat- sheet cells operating in a laminar, cross-flow regime. Membranes were fouled by challenging these units with solutions containing BSA or amylase at levels high as 1g/L. Baseline conditions were established by running ultrapure water thorough the system for at least 24h. In a series of independent trials, the

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membranes were then challenged with different protein formulations (pH, ionic strength, protein mass) for 5 to 25h depending on the fouling response. During all tests, the in-situ detection of proteins associating with the membranes used ultrasonic frequency- domain reflectometry (UFDR) integrated with a fast Fourier transform protocol to process the signals. Time-domain signals of acoustic scans from ultrasonic transducers mounted on cross-flow cells were transformed into amplitude versus frequency distributions. From these distributions, reflected power was obtained, and standard statistical indices were used to report and characterize the distributions. Following cross-flow cell tests, membrane samples were analyzed using ESEM, and the proteins associated with the membranes were determined using a bicinchoninic protein assay.

Depending on the fouling challenge conditions, permeate flow-rate decreased in a range between 40-90%. Permeate flow-rate responses, and patterns of corresponding acoustic reflection power changes, indicated that both internal membrane and surface deposition occurred, and could be identified as separate fouling mechanisms during some challenge conditions. The permeate-flow rate decline data can be described using the combined pore blockage, pore constriction, and cake filtration model. The best fit model parameters can be independently obtained based on the property of the feed and membrane characteristics. In some instances however, transducers were unable to detect reflected power changes even after significant permeate-flow rate decline occurred. This phenomenon could be explained by the fact that permeate flow-rate observations are derived from overall membrane behavior, whereas UFDR is applied in a sentinel format, which reports acoustic responses of small area (point) observations on a very short timescales. In addition, membrane- associated protein deposits are visco-elastic, and can (and likely do) reposition on or through a membrane during the course of a fouling challenge; this can manifest in a wide variability of reflected power changes as protein density changes on a local scale during a test. Biochemical assays of protein concentrations associated with membranes and ESEM micrographs confirmed that a significant heterogeneity of protein deposition was in part responsible for the fouling behavior and local density changes observed by UFDR. Where protein concentration on the membrane varied between 5 to 100µg/cm2, ESEM observations showed non- uniformity of protein deposition in a capricious patchy array, with a significant amount of clean membrane area exposed; beyond this range however (100µg/cm2), continuous protein layers were observed on challenged membrane surfaces.

The use of fouling models in combination with non-invasive, real-time monitoring provides a unique capability to improve the fundamental understanding and control of MF membrane fouling by commercially significant proteinaceous biopolymers.

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Membrane Fouling - General Topics – 2

Monday July 14, 10:15 AM-10:45 AM, O’ahu

Assessment of Ultrasound as Fouling Control Technique in Crossflow Microfiltration for the Treatment of Produced Water

S. Silalahi (Speaker), Norwegian University of Science and Technology, Norwegian, [email protected] T. Leiknes, Norwegian University of Science and Technology, Norwegian

Produced water is contaminated water containing residual concentrations of chemical additives, dispersed oil in water (o/w) emulsions, dissolved organic compounds, traces of heavy metals and inorganic compounds, which is extracted during oil and gas drilling operations. In 2005, the total amount of produced water discharged to the North Sea was about 177 million m3, resulting in approximately 2800 m3 of oil being discharged to the sea. Regulations that govern the allowable discharge of oil into sea from offshore installation on the Norwegian Continental Shelf (NCS) were 40 mg/l of oil in water (up to end of 2006) and is currently 30 mg/l. More stringent regulations are expected in the future.

Membrane separation has the potential for very effective separation of oil from water. It has been applied for the treatment of produced water and oily wastewaters. The major drawback of membrane technology is the fouling phenomena, which in the long term will cause a progressive decrease of flux and induce a loss of separation efficiency. Fouling mitigation has been approached by; feed pre-treatment, modified membrane surface material, flow manipulations (i.e. backpulsing, flow reversal, turbulence promoters etc.), applying additional force fields (i.e. electrical fields and ultrasound fields). Fouling can also be limited by operating the membrane under certain hydrodynamic conditions.

Ultrasound is a potential technique that can be used for membrane fouling control and cleaning. The advantages of US to control membrane fouling are no chemical use and no interruption during filtration. US dislodges fouling layers formed on the membrane due to effects such as acoustic streaming, microstreaming, microstreamers, microjets, and shock waves. The objective of this study is to asses US for fouling control for treatment of produced water. The effectiveness of ultrasound-assisted membrane filtration was determined by various parameters i.e. ultrasound frequency and power, feed properties, membrane properties and operation condition.

An analogue produced water was prepared by dispersing oil in surfactant and water. Solid particles, scaling and corrosion inhibitor were also added to make-up the analogue for Ceramic Al2O3 membrane with pore sizes of 0.1, 0.2 and 0.5µm

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in crossflow mode operation were investigated. US with frequencies 25, 45, and 100 kHz respectively and power intensity of 600W were tested.

The effect of power intensity, frequency, mode of US operation (continuous vs. intermittent) for different membrane pore sizes will be presented. Tests are done with different feed properties. An optimum power intensity and frequency to control the fouling was observed. Presence of particles plays a significant role to reduce the performance by attenuating the ultrasound power.

Keywords: Produced water, microfiltration, fouling, ultrasound

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Membrane Fouling - General Topics – 3

Monday July 14, 10:45 AM-11:15 AM, O’ahu

Impact of Diluate Solution Composition in Protein and Magnesium on Membrane Fouling During Conventional ED

G. Pourcelly (Speaker), Institut Europeen des Membranes, France, [email protected] C. Casademont, University Laval, Québec, Canada E. Ayala Bribiesca, Institut Nutraceutiques et Aliments Fonctionnels, Québec, Canada M. Araya Farias, Institut Nutraceutiques et Aliments Fonctionnels, Québec, Canada L. Bazinet, Institut Nutraceutiques et Aliments Fonctionnels, Québec, Canada

Fouling formation is among the most important limitations in electrodialysis (ED) processes. Build- up of fouling film causes an increase in resistance, which deteriorates the performance of process and can eventually lead to membrane integrity alteration [1]. Numerous studies have been done on the identification of species causing fouling [2-3], but most of these works are directly related to anion- exchange membrane (AEM), since their fouling susceptibility is higher than that of cation- exchange membrane (CEM). But recently, the formation of a mineral fouling on CEM and AEM has been reported during conventional ED of different solutions of CaCl2 and Na2CO3 [2]. Furthermore, during the production of high purity bovine milk casein isolates from skim milk by bipolar membrane electroacidification (BMEA), a further step in the ED process evolution, where bipolar membranes allow the dissociation of water molecules in protons and hydroxyl ions under an electric field, two types of fouling were observed. A mineral fouling identified as a mixture of CaCO3 and Ca(OH)2 was observed on both sides and inside the CEM as well as a slight protein fouling on the CEM. For the CaCO3 mineral fouling, it was suggested that nucleation would be the controlling step, since crystallization occurred when the nuclei were formed and the solution was supersaturated [4] and that Mg, present in milk at an average concentration of 105 mg/kg would initiate and structure the formation of CaCO3 [5-

6]. However the impact of Mg on the formation of a CaCO3 fouling at the interface of a CEM has never been studied. In addition, not much work characterizing protein-caused fouling of ED membranes has been found.

The aim was to study the effect of the concentrate solution pH, the composition in calcium, carbonate, magnesium (at different ratios of Mg/Ca) and protein of the diluate solution to be treated by conventional ED on the fouling of ion- exchange membranes. Conductivity, system resistance, pH of the diluate and cation migration were monitored to follow the evolution of the demineralization. Acidic and neutral conditions led to protein film formation over the diluate side of the AEM, but basic conditions prevented its formation. Protein fouling on CEM was not visually apparent. CEM presented mineral fouling only in basic concentrate conditions when calcium was present, which would precipitate as calcium

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hydroxide. For Mg/Ca = 0, the fouling observed on the surface in contact with the basified concentrate was only formed by Ca(OH)2. As soon as Mg was introduced into the solution treated, CaCO3 was observed. Furthermore, the X-ray diffraction results also identified the CaCO3 observed as calcite. From Mg/Ca = 1/20 to 1/5, the amount of calcite increased with the Mg concentration. For Mg/Ca > 1/5, an undesired fouling appeared on each side of the CEM and on the concentrate side of the AEM whereas, under this ratio, no fouling was detected on AEM and only on the CEM concentrate side. The membrane fouling mainly affected the ED efficiency in basic conditions. Starting from Mg/Ca = 1/5, the CEM permselectivity was significantly affected and a drastic decrease in the current efficiency occurred. The direct consequence of this alteration was the migration of hydroxyl ions through the CEM toward the anode. The hydroxyl leaching also explains the mineral deposit observed on the diluate side of the CEM. Mineral fouling on the concentrate side of AEM was due to recirculation and mixture of both anion and cation-receiving streams. The stack configuration used allowed calcium to migrate through CEM and, by recirculation, to be in contact with the AEM and thus to precipitate on its surface, as CaCO3 and Ca(OH)2.

According to these results, the separation of the concentrate stream in two different loops would prevent formation of both, mineral and protein foulings. An acidic or neutral pH condition should be maintained for the cation-receiving stream in order to prevent mineral fouling on the concentrate side of CEM. This loop must remain independent to the anion receiving one. A basic pH should be maintained for the latter to prevent formation of a protein film over the AEM surface. Mineral fouling on AEM will no longer form, as calcium will not enter in contact with the concentrate side of such membrane.

[1]: M.Bleha, G.Tishchenko, V.Sumberova, V.Kudeala, Desalination 86(1991)73

[2]: L.Bazinet, M.Araya-Farias, J.Colloïd Interface Sci., 286(2005)639

[3]: E. Ayala-Bribiesca, G.Pourcelly, L.Bazinet, J.Colloid Interf Sci, 308(2007)182

[4]: T.H.Chong, R.Sheikholeslami, Chemical Engineering Sci., 56(2001)5391

[5]: F.C.Meldrum, S.T.Hyde, J. Crystal Growth, 231(2001)544

[6]: E.Loste, R.M.Wilson, R.Seshadri, F.C.Meldrum, J. Crystal Growth, 254(2003)206

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Membrane Fouling - General Topics – 4

Monday July 14, 11:15 AM-11:45 AM, O’ahu

MBR Activated Sludge Filterability Alteration in Stress Circumstances

S. Geilvoet (Speaker), Delft University of Technology, The Netherlands, [email protected] J. Van der Graaf, Delft University of Technology, The Netherlands A. Van NIeuwenhuijzen, Delft University of Technology, The Netherlands

Fouling in membrane bioreactor (MBR) systems is an extensively investigated research topic. Significant progress has been made in understanding fouling, but nevertheless it still is a major point of attention in full-scale MBR operation and many questions still remain unanswered. Simply stated the fouling potential in a membrane bioreactor (MBR) system is depending on three factors: membrane properties, membrane operation and activated sludge properties. Because in practice every MBR plant has its own unique combination of these three factors, it is difficult to determine which factor(s) is/are responsible in case of fouling problems. Delft University of Technology has developed a filtration characterization method that aims at determining the role of sludge characteristics in the filtration process. Sludge samples collected from different full-scale MBR plants or under different circumstances are filtrated with the same membrane under exact identical operational circumstances with the Delft Filtration Characterization method (DFCm). In this way differences in filterability can be related exclusively to the quality of the sludge sample.

Several researchers demonstrated that when activated sludge is experiencing stress conditions severe fouling problems can occur. In this research two different stress conditions were simulated. Activated sludge samples collected from full-scale MBR Heenvliet in the Netherlands were exposed to a long period without aeration and to a short period of high shear stress conditions induced by a centrifugal pump. Goal of the research was to examine the effect of these stress conditions on the sludge filterability and characteristics and the ability of the sludge to recover from it. The filtration characterization experiments were accompanied by several sludge quality analyses: the concentration Soluble Microbial Products (SMP), Particle Size Distribution (PSD) in the submicron range of the free water and sludge viscosity were measured.

The results show that exposing the sludge to stress conditions lead to deflocculation of the sludge which was expressed in the release of SMP and of colloidal particles in the free water and a deterioration of the filterability. When the sludge was subsequently preserved in continuous aerated conditions, it showed a strong ability to recover from the stress circumstances. The sludge quality deterioration which was obtained in approximately three days of anoxic circumstances was undone in a period of only several hours. Together with the

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improvement of filterability also the SMP concentrations and the number of colloidal particles in the free water decreased. From this research it was concluded that flocculation is a very important parameter for sludge filtration. Looking after favorable flocculation conditions in MBR as soon as the sludge reaches the membrane tank is an important aspect for good MBR operation.

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Membrane Fouling - General Topics – 5

Monday July 14, 11:45 AM-12:15 PM, O’ahu

Scale-up of Lab Investigations on Fouling in MBR Potentials and Limitations

M. Kraume (Speaker), Technische Universität Berlin, Chair of Chemical Engineering, Germany, [email protected] D. Wedi, Engineering Office ATM T. de la Torre, Berlin Centre of Competence for Water J. Schaller, Technische Universität Berlin, Chair of Chemical Engineering, Germany V. Iversen, Technische Universität Berlin, Chair of Chemical Engineering, Germany A. Drews, Technische Universität Berlin, Chair of Chemical Engineering, Germany

Objective Despite the large number of publications, membrane fouling still is not well understood due to the complexity of the interacting phenomena and the multitude of module and reactor configurations as well as wastewaters and operating conditions. To reduce the number of influencing factors, often lab trials are carried out where only the parameter of interest is to be varied. These are either filtration experiments (e.g., filtration mechanisms, fouling rate) carried out with real or model feeds, biological investigations (e.g., soluble microbial products (SMP) occurrence), a combination of both (e.g., fouling propensity of SMP formed under different conditions) or concern suited cleaning protocols. However, the outcomes of such studies are frequently inconsistent or even contradictory. The representativeness of conclusions drawn from such trials is thus highly questionable - both quantitatively and qualitatively. In the light of such contradictions, this paper aims at answering the question how representative of full scale operation lab trials are or indeed can be, i.e., what can be expected from them at all considering their inherent differences from technical operating conditions. Summarizing the different experiences, guidelines for a ‘good laboratory practice’ will be derived concerning appropriate experimental set-ups and corresponding test protocols.

Results

Initially, types of experiments and distinct differences are analyzed. In the second part, results from own experiences in lab (1-140 L), pilot (1.5 m³) and full scale (250-9,200 p.e.) together with data from literature are exemplarily discussed to highlight potentials and limitations of different experimental approaches. In general, lab scale experiments are an indispensable tool for fundamental fouling research. With regards to their value and applicability to full scale it will be stated that: · Properly done short-term experiments based on suited protocols can be used to characterize the filterability and the relative fouling propensity of different sludges. The absolute values of measured fouling rates, however, are never appropriate to describe long-term operation in full

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scale where fouling rates are commonly at least one order of magnitude lower. The discrimination whether the reason for a sudden permeability decrease in full scale is a low filterability of the activated sludge or, e.g., module sludging can be realised on this basis. Hence a regular monitoring of sludge behaviors in full scale plants is hereby possible. To some extent, data can be used for model identification to analyse the mechanisms that are responsible for the observed fouling rates. Due to the interactions of ambient conditions in full scale, defined lab studies are the only way to independently study influences on biological kinetics. Cleaning success can be transferred qualitatively to full scale but also not quantitatively. Thus, it will be demonstrated that lab scale experiments can be meaningful for full scale operation only if the following preconditions are fulfilled: Hydrodynamics must be comparable to achieve qualitatively comparable fouling. Aeration rate, crossflow velocity and geometry (channel width etc.) must be the same in both scales. Due to the fluid-structure interactions this can hardly be achieved for hollow fibres. Operating conditions (constant TMP/constant flux) must be identical to achieve comparable quality of the fouling layer. Even such alleged banalities like test cell orientation must be carefully considered. Fresh sludge from the full scale plant must be used or in-situ experiments must be carried out in order to avoid effects due to starvation/disintegration etc. of the sludge during sludge storage and shipment. If any of these stipulations is not met, researchers and operators should be aware that the inherently limited representativeness of results gained in lab scale is restricted even further.

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Membrane Fouling - General Topics – 6

Monday July 14, 12:15 PM-12:45 PM, O’ahu

Visual Characterization of Fouling Behaviour By Activated Sludge Model Solutions

Y. Marselina, University of New South Wales, Sydney, Australia P. Le-Clech, (Speaker) University of New South Wales, Sydney, Australia R. Stuetz, University of New South Wales, Sydney, Australia V. Chen, University of New South Wales, Sydney, Australia, [email protected]

Fouling can be easily characterized with the hydraulic performances of the membrane, such as transmembrane pressure (TMP), flux and resistances. Better insight of fouling can also be obtained by using visualization methods, which include invasive and non-invasive techniques. The non-invasive techniques provide some advantages over the invasive techniques, by analyzing the membrane without removing it from its membrane module. Direct observation (DO), which consists of modified crossflow module, microscope and video camera, is one of the non-invasive techniques that can be used to visualize the fouling deposition and removal on the hollow fibre membrane.

In this paper, the DO technique will be used to further characterize the fouling behaviour for extracellular polymeric substances (EPS) in activated sludge for membrane bioreactor (MBR) application. Recent research based on the effect of the feed on MBR fouling has been conducted by using model solutions to mimic the major foulants found in the mixed liquor. The bentonite particulate can be used to approximate the behaviour of biomass particles and flocs. The alginate and xanthan gum can be used to model the carbohydrate fraction and bovine serum albumin (BSA) used to model the protein fraction of the EPS material in the biomass. The glycerol was used to change the viscosity property of the fluid and model the Newtonian fluid. Moreover, the xanthan gum was used to model the non-Newtonian fluid.

During the filtration of the bentonite - alginate mixture, the fouling deposition mechanisms were showed by the formation of the stagnant and fluidised layer on the membrane surface. When the concentration of alginate in the bentonite - alginate mixture was increased, the TMP and specific cake resistance increased but the stagnant fouling thickness (Hc) decreased, indicating dense fouling layer. Although the Hc decreased with the alginate concentration in the mixture, the cleaning time required to remove most of the reversible fouling increased. This showed that the addition of alginate contributed to the changes in the fouling layer morphology by increasing the cohesion bonding between deposited foulants and the adhesion bonding between foulants and membrane. It was observed that the fouling removal mechanisms in the presence of alginate were

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observed in two subsequence phenomena: (1) cake expansion and gradual erosion, followed by (2) gradual erosion and removal in agglomerates.

The effects of different biopolymer natures and feed viscosities on particulate fouling were also studied by observing the fouling deposition and removal of the mixtures in the presence of bentonite, alginate, BSA, glycerol and xanthan gum. The cake properties were better characterized with the TMP, resistances, visualization during fouling deposition and removal. The observation during fouling removal showed how the cohesivity of the fouling structures formed during the filtration.

The presentation of this work will include videos of the fouling deposition and removal obtained during our experiments.

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Membrane Modeling I - Fundamental Approaches – 1 – Keynote

Monday July 14, 9:30 AM-10:15 AM, Waialua

Membrane Analysis and Simulation System (MASS)

R. Faibish (Speaker), Argonne National Laboratory, Argonne, IL, USA, [email protected] D. Pointer, Argonne National Laboratory, Argonne, IL, USA B. Roux, Argonne National Laboratory/University of Chicago, Argonne, IL, USA A. Tentner, Argonne National Laboratory, Argonne, IL, USA

The MASS project is aimed to develop a novel and innovative simulation tool to predict membrane properties and performance. The simulation tool will be sufficiently robust to a-priori describe the fundamental membrane properties and their relationship to membrane processes. The tool will integrate interactions from the molecular level through their macroscopic impacts. It will guide the prediction of membrane properties and performance and ultimately be a valuable resource for predictive economics of a wide range of separations. The tool will utilize computational fluid dynamics, lattice Boltzmann method modeling, molecular dynamic modeling, user guidance feedback (UGF) based on artificial intelligence (‘thinking model’), and system analysis. Upon appropriate input, the model will then yield information on the feasibility of the desired separation, materials selection, recommended operating parameters, and overall process economics, among other possible outputs. The proposed ‘full picture’ modeling tool will provide integrated macro- and micro-scale predictions to guide selection of the proper membrane process, materials, and overall system for the desired separation. There are three scales at which to attempt solutions: 1) Process optimization using existing, characterized membranes; 2) Design of new membranes based upon macroscopic, empirical characterization of membrane materials; 3) Predict the behavior of a membrane from atomistic scale principles. The paper will present the results and progress to date.

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Membrane Modeling I - Fundamental Approaches – 2

Monday July 14, 10:15 AM-10:45 AM, Waialua

Development of Novel Molecular Modeling Technique for Membrane Fouling in Water Treatments

H. Takaba (Speaker), Tohoku University, Sendai, Japan, [email protected] A. Suzuki, Tohoku University, Sendai, Japan R. Sahnoun, Tohoku University, Sendai, Japan M. Koyama, Tohoku University, Sendai, Japan H. Tsuboi, Tohoku University, Sendai, Japan N. Hatakeyama, Tohoku University, Sendai, Japan A. Endou, Tohoku University, Sendai, Japan C. Del Carpio, Tohoku University, Sendai, Japan M. Kubo, Tohoku University, Sendai, Japan T. Kawakatsu, Kurita Water Industries Ltd., Tochigi, Japan I. Nishida, Kurita Water Industries Ltd., Tochigi, Japan Y. Watanabe, Kurita Water Industries Ltd., Tochigi, Japan S. Nakao, The University of Tokyo, Tokyo, Japan A. Miyamoto, Tohoku University, Sendai, Japan

Novel molecular modeling technique for investigation of fouling mechanism in water treatments using membranes based on quantum molecular dynamics was developed. The developed technique enables to calculate interactions between soluble organic compounds and a membrane surface in aqueous condition so that it is applicable to predict molecular behaviors of organic compounds in UF/NF/RO membrane processes. In this technique, the interaction in aqueous condition was represented by potential of mean force (PMF). Novel scheme of molecular dynamics using the PMF has an advantage of computational cost in evaluating interaction from water bulk, which makes possible a large scale calculation. We applied this technique to the simulation of various surfactants coagulation and adsorption on aromatic poly-amide RO membrane and revealed the membrane fouling mechanism by the surfactant in treated water from atomistic level.

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Membrane Modeling I - Fundamental Approaches – 3

Monday July 14, 10:45 AM-11:15 AM, Waialua

Electroosmotic Flow in a Lysozyme Crystal: Molecular Dynamics Simulation

Z. Hu, National University of Singapore, Singapore J. Jiang (Speaker), National University of Singapore, Singapore, [email protected]

The electroosmotic flow of electrolyte solution (mixed NaCl and CaCl2) in a lysozyme crystalline membrane is investigated using nonequilibrium molecular dynamics simulation. The stability of lysozyme is observed to slightly decrease upon exposure to the electric field. Water molecules align preferentially parallel to the electric field, and ions exhibit layered structures near the protein surface. The hydration numbers of ions and the coordination Cl- numbers of cations are found to be electric-field independent. The drift velocities of ions vary with the ion charge and the electric-field strength, and are affected by the stream of oppositely charged ions. Nonequilibrium and equilibrium simulations give a close electrical conductivity for the system.

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Membrane Modeling I - Fundamental Approaches – 4 Monday July 14, 11:15 AM-11:45 AM, Waialua

Theoretical Analysis of the Effects of Asymmetric Membrane Structure on Fouling during Microfiltration

W. Li, University of Cincinnati, Cincinnati, OH, USA C. Duclos-Orsello, Millipore Corp., Billerica, MA, USA C. Ho (Speaker), University of Cincinnati, Cincinnati, OH, USA, [email protected]

There is growing interest in the use of both asymmetric and composite membranes for microfiltration and ultrafiltration processes. This includes particle removal applications in the semiconductor industry and virus clearance in biopharmaceutical applications. Filter fouling plays an important role in these processes. Though flux decline models have been developed for homogeneous membranes, the effects of asymmetric membrane structure on flux decline behavior remains poorly understood on a fundamental level. Here, we develop a theoretical model to describe the effects of asymmetric membrane structure on flux decline. The asymmetric structure was described by the spatial variation in Darcy permeability in the directions normal to and parallel to the membrane surface. The velocity profile and flux decline due to pore blockage were described using Darcy�s law and a pore blockage and cake filtration model. Flux decline data were obtained using pseudo-composite membranes with highly interconnected polyvinylidene fluoride membranes (PVDF) and straight through pore polycarbonate track etched membranes (PCTE). Model composite membranes were formed by layering PCTE or PVDF membranes with different pore sizes on top of each other. Flux decline data for the composite membrane were in good agreement with model calculations. The results provide important insights into the effects of asymmetric membrane pore structures on flux decline.

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Membrane Modeling I - Fundamental Approaches – 5

Monday July 14, 11:45 AM-12:15 PM, Waialua

Modeling Virus Filtration: A Population Balance Approach

A. Pavanasam, University of New South Wales, Australia A. Abbas (Speaker), University of Sydney, Australia, [email protected] S. Ansumali, Nanyang Technological University, Singapore V. Chen, University of New South Wales, Australia

Background: Ultrafiltration (UF) is proving to be a promising operation in the biopharmaceutical industry for both virus purification and clearance operations. In this paper, we present a detailed model for virus UF that is based on population balance theory. The proposed model is validated experimentally.

Modeling: Numerous process models have been presented in the literature that describes the performance of UF operations [1-6]. Typically UF models predict permeate flux decline, the percent rejection and solute concentration in the retentate under varying feed concentrations, membrane fouling and changes in pressure drop. The model of this work addresses these variables� interactions and further takes into account particle suspension properties, more specifically particle polydispersity parameters. Population balance theory lays the foundation for this model where a discrete set of equations can be written to describe the population density of each particle size class of the permeate (or retentate).

The developed population balance equation (PBE) is accompanied by a specific initial condition, mass balance and other constitutive relations together forming the population balance model (PBM). In developing the PBM, several assumptions are considered including: tangential flow, laminar flow in pores, monodisperse pore sizes, constant feed flow and concentration. The model is solved using gPROMS package (Process Systems Enterprise, UK).

Model Validation: Experiments were conducted for the purpose of model validation. In all the experiments, the temperature was set to 25C and specially prepared 0.1% Latex particles at various pump speeds were used. The latex particles were used to simulate the real virus ones. Samples (from permeate and retentate) were collected at regular time intervals. These samples were analyzed for the particle size distribution using dynamic laser particle size measurement.

Results: Preliminary modeling results are promising indicating that the mechanics of the PBM, which are to a large extent statistical in nature, are close to the region of the experimental data. The existing mismatch between the model and the experimental data is attributable to the simplifications of the assumptions involved. The PBM is simple yet serves as a powerful predictive tool for the study

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of the impact of the operating parameters on the permeate particle phase viz. quality of permeate. Particle mean size as well as other particle characteristics like particle size distribution etc can be derived from the PBM leading to better understanding of the underlying UF interactions and mechanisms.

References:

[1] Y Lee, M M Clark, Modeling of flux decline during crossflow ultrafiltration of colloidal suspensions, J. Membrane Sci., 149 (1998), 181.

[2] M M Sharma and Y C Yortsos, Transport of particulate suspensions in porous media: Model formulation, AIChe J, 33 (1987), 1636.

[3] G A Denisov, Theory of concentration polarization in cross-flow Ultrafiltration: Gel layer model and osmotic pressure model, J. Membrane Sci., 91 (1994), 173.

[4] G L Baruah, A Venkiteshwaran, and G Belfort, Global Model for Optimizing Crossflow Microfiltration and Ultrafiltration Processes: A New Predictive and Design Tool, Biotechnology Prog., 21 (2005), 1013.

[5] J.G.Wijmans, S.Nakao and C.A.Smolders, Flux Limitation in Ultrafiltration: Osmotic Pressure Model and Gel Layer Model, J. Membrane Sci., 20 (1984), 115.

[6] M.N.Tekic, J Kurjacki and Gy Vatai, Modeling of batch Ultrafiltration, Chemical Engg. Journal, 61 (1996), 157.

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Membrane Modeling I - Fundamental Approaches – 6

Monday July 14, 12:15 PM-12:45 PM, Waialua

Direct Simulation of Particle Migration in Cross-Flow Microfiltration

M. Fujita (Speaker), The University of Tokyo, Tokyo, Japan, [email protected] K. Oda, The University of Tokyo, Tokyo, Japan K. Akamatsu, The University of Tokyo, Tokyo, Japan S. Nakao, The University of Tokyo, Tokyo, Japan

A direct simulation of particle migration due to a shear-induced lift force in a cross-flow microfiltration is carried out without any analytical or empirical models of the lift force. Both the motion of particles and the flow of liquid are simultaneously computed based on a Newtonian dynamics and the fluctuating Navier-Stokes equation that contain a variety of particle-to-particle interactions and particle-to-liquid hydrodynamic interaction. The hydrodynamic interaction is accurately calculated because pressure and viscous stress on the particle surface are evaluated on the computational lattice whose spacing is quite smaller than the particle size. The present simulation can resolve not only lift force exerted on a single particle but also lift forces exerted on concentrated many particles in the vicinity of a membrane surface. The simulation result shows the relationship between the particle size and the velocity of particle migration in a range of particle concentration.

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Oral Presentation Abstracts

Afternoon Session

Monday, July 14, 2008

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Hybrid and Novel Processes I – 1 – Keynote

Monday July 14, 2:15 PM-3:00 PM, Kaua’i

Scaleable Membrane Separations for the Lignocellulosic-to-Ethanol Biorefinery?

J. Pellegrino (Speaker), University of Colorado, Boulder, CO, USA, [email protected] K. Colyar, University of Colorado, Boulder, CO, USA M. Gutierrez-Padilla, University of Colorado, Boulder, CO, USA J. Hettenhaus, cea Inc., Charlotte, NC, USA D. Schell, National Renewable Energy Laboratory, Golden, CO, USA

There are many challenges to realizing a significant biomass-to-fuels industry based on lignocellulosic feedstocks in the US. One of the significant issues is how to economically address highly distributed, low density feedstock supplies that arise from agricultural (such as, corn stover) and forestry waste material. In addition, ways to recover and recycle fertilizer micronutrients (inculcated wthin the biomass) back to the fields, and bring the farming community further along the value chain, are all important criteria for successful growth of this important industry. To these ends, we will present a brief overview of the opportunities for membrane processes within the lignocellulosic biorefinery and ways that these processes may potentially mitigate the economic penalties associated with small scale plants. We will report bench-scale studies on leaching of micronutrients from stored wet stover, co-harvested with the corn in a cooperative, and the recovery and recycle of fertilizer anions and cations, as well as the water. We will also present the broad results from several other membrane processes that recover and recycle water, and/or fractionate by-products from this stover as it undergoes pre-hydrolysis using a novel reactor designed for small scale processing. And from the ethanol fuel product side, we have performed separation studies on the removal of small organic molecules, which provide inhibition of the fermentative organisms, in order to recycle water back to the ethanol fermentor from the beer column. A variety of commercial membranes have been considered for all these operations, and initial figures-of-merit have been obtained and will be discussed within the context of desirable improvements in materials and/or process configurations.

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Hybrid and Novel Processes I – 2

Monday July 14, 3:00 PM-3:30 PM, Kaua’i

Reducing the Energy Demand of Bio-Ethanol through Salt-Extractive Distillation and Electrodialysis

P. Pfromm (Speaker), Kansas State University, Manhattan, KS, USA, [email protected] M. Hussain, Kansas State University, Manhattan, KS, USA

Bio-ethanol from corn currently consumes about 34,000 BTU in form of natural gas to produce one gallon of ethanol representing 76,000 BTU as lower heating value (U.S. industrial practice data, 2007). Separating ethanol from water consumes about 40% of the natural gas demand cited above. Saline extractive distillation of alcohol-water mixtures and fermentation broth has been considered elsewhere and fairly comprehensive experimental data, thermodynamic data, and simulations are available. Potentially very significant energy savings and process simplifications have been found. However, the recovery and recycling of the salt used to facilitate distillation has not been addressed. Electrodialysis is uniquely suited for salt recovery from the saline extractive distillation column bottoms since salt is selectively removed from the solution (no water is evaporated) and the electrodialysis membranes and overall fluid handling are tolerant to fermentation broth and even to entrained particulate matter. Concepts, modeling, and experimental data for electrodialysis-enabled salt extractive ethanol distillation will be shown. Aqueous/aqueous and aqueous/ethanol electrodialysis will be discussed.

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Hybrid and Novel Processes I – 3

Monday July 14, 3:30 PM-4:00 PM, Kaua’i

Membrane Separation Techniques in the Continuous Fermentation and Separation of Butanol

J. Du (Speaker), University of Arkansas, Fayetteville, AR, USA R. Beitle, University of Arkansas, Fayetteville, AR, USA E. Clausen, University of Arkansas, Fayetteville, AR, USA J. Carrier, University of Arkansas, Fayetteville, AR, USA J. Hestekin, University of Arkansas, Fayetteville, AR, USA, [email protected]

Butanol is an excellent substitution of gasoline, which can use in the interior combustion engine without any modification of engine. About 50 years ago, the acetone-butanol-ethanol fermentation process, employing bacterium Clostridium acetobutylicum to convert biomass to butanol, was the most popular way to produce butanol. But this process has some drawbacks in that many bi-products are produced. Besides butanol, the fermentation also produces acetic, butyric and lactic acids when fermentation passes through acidogenesis phase..

In this project, we propose a continuous two stage fermentation/membrane separation system that is based on the work of Ramey (1998) where two organisms, Clostridium acetobutylicum and Clostridium tyrobutyricum, are used in tandem to produce butyric acid (with lactic and acetic) in the first fermentation and butanol (with acetone and ethanol) in the second fermentation. Ramey (1998) proposed liquid-liquid extraction for product removal, but this process has problems with solvent entrainment and selectivity. We are working to demonstrate that selective removal of butyric acid from the first stage by a novel membrane technique that will produce higher yields and productivity than current technology.

The technology that we are exploring for this separation is electrodeionization (EDI) which is connected to a continuous fermentation with cell recycle of the Clostridium tyrobutyricum. EDI is a technology that has been used for pure water purification, but is relatively unexplored in product separation, especially selective removal of ions. Early results show that EDI is more selective than electrodialysis (>2X increased selectivity of butyrate over lactate as compared to ED) and can operate to a lower concentration (Arora et al., 2007), thus making the whole process more attractive. We will demonstrate the first continuous production of butyric acid by Clostridium tyrobutyricum with EDI product separation and show the effects of reduced inhibition, substrate recycling, and media recycling. We will also demonstrate a comprehensive model on the EDI fermentation process.

References

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Arora, M.B., J.A. Hestekin, S.W. Snyder, E.J. St. Martin, M.I. Donnelly, C. Sanville-Millard and Y.J. Lin, ‘The Separative Bioreactor: A Continuous Separation Process for the Simultaneous Production and Direct Capture of Organic Acids’, Separation Science Technology, 42, 2519-2538, 2007.

Ramey, D.E., ‘Continuous, Two Stage, Dual Path Anaerobic Fermentation of Butanol and Other Organic Solvents Using Two Different Strains of Bacteria’, U.S. Patent 5,753,474, May 19, 1998.

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Hybrid and Novel Processes I – 4

Monday July 14, 4:00 PM-4:30 PM, Kaua’i

Power Generation by Reverse Electrodialysis

P. Dlugolecki (Speaker), University of Twente, Wetsus, The Netherlands, [email protected] K. Nymeijer, University of Twente, The Netherlands S. Metz, University of Twente, Wetsus, The Netherlands M. Wessling, University of Twente, The Netherlands

Introduction Membrane technology provides an opportunity to gain sustainable energy from salinity gradients via reverse electrodialysis [1-4]. RED can be applied where two solutions of different salinity gradient mix, e.g. where river water flows into the sea. Ion-exchange membrane properties (resistance, selectivity, ion exchange capacity, structure and thickness) affect the performance of the RED process. Up to now it is not known which membranes properties are important for the RED process. Therefore, we determined the membrane properties of several commercial membranes and compared them for their RED performance with a theoretical model [4].

Theory In RED, a concentrated salt solution and a fresh water are brought into contact through an alternating series of anion exchange membranes (AEM) and cation exchange membranes (CEM). Anions migrate through the AEM towards the anode and cations move through the CEM towards the cathode. The difference in chemical potential between both solutions is the driving force for this process. Electrons migrate from anode to cathode through an external electrical circuit in order to maintain electro-neutrality in the cathode and anode compartment. This electron migration can be used to generate electrical power. The theoretical value of the chemical potential for an aqueous monovalent electrolyte can be calculated using the Nerst equation. Results and discussion The theoretical membrane model for reverse electrodialysis was used to predict the theoretical power density obtainable using experimental membrane characterization data. Results show that large increases in power density can be obtained by decreasing the membrane resistance and the thickness of the river water compartment. Improvement of membrane properties has only a significant effect if such small membrane spacing is applied. When the membrane spacing is 150µm the membrane resistance becomes a dominant factor to generate energy. When 600µm spacer was applied the membrane selectivity seems to play an equal role with the membrane resistance. However, with this stack configuration membrane performance has less influence on obtained power density. According to membrane model is feasible to reach the power density up to 5 W/m2 with commercial available membranes. Tailor-made membranes can improve this performance even further more.

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Conclusions Reverse electrodialysis is a non-polluting, sustainable technology to generate direct electricity from the mixing of fresh and salt water. The ion exchange membranes are the key elements in RED. Based on the results, the best benchmarked commercially available anion exchange membranes reach a power density of more than 5 W/m2 whereas the best cation exchange membranes show a theoretical power density of more than 4 W/m2. According to the membrane model calculations power densities higher than 6 W/m2 could be obtained by using thin spacers and tailor made membranes with low membrane resistance and high permselectivity especially designed for reverse electrodialysis. This makes RED a potentially attractive and alternative for sustainable energy production.

Reference

1. R.E. Pattle, Production of Electric Power by mixing Fresh and Salt Water in the Hydroelectric Pile, Nature, 174 (1954) 660.

2. J.W. Post, J. Veerman, H.V.M. Hamelers, G.J.W. Euverink, S.J. Metz, K. Nymeijer, C.J.N. Buisman, Salinity-gradient power: Evaluation of pressure- retarded osmosis and reverse electrodialysis, Journal of Membrane Science, 288 (2007) 218.

3. J. Veerman, J.W. Post, M. Saakes, S.J. Metz, G.J. Harmsen, Reducing power losses caused by ionic shortcut currents in reverse electrodialysis stacks by a validated model, Journal of Membrane Science, 310 (2008) 418-430.

4. P. Dlugolecki, K. Nymeijer, S. Metz, M. Wessling, Current status of ion exchange membranes for power generation from salinity gradients, Journal of Membrane Science, (2008) Submitted.

5. J.N. Weinstein, F.B.J.W. Leitz, Electric power from differences in salinity: the dialytic battery, Science, 191 (1976) 557.

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Hybrid and Novel Processes I – 5

Monday July 14, 4:30 PM-5:00 PM, Kaua’i

Reverse Electrodialysis: Energy Recovery from Controlled Mixing Salt and Fresh Water

J. Post (Speaker), Wageningen University, Wetsus, The Netherlands H. Hamelers, Wageningen University, Wetsus, The Netherlands, [email protected] C. Buisman, Wageningen University, Wetsus, The Netherlands

The global potential to obtain clean energy from mixing river water with sea water is considerable. The gross power potential of this unconventional energy source was estimated to be 2.4-2.6 TW [1, 2] when the average discharges of all rivers were used. It was assumed [1, 3] that from each cubic meter of river water that flows into the sea, 2.3 MJ of work could be made available. A main question is how much of this salinity-gradient energy can be converted into sustainable electricity. Recently, we reviewed literature on two membrane-based techniques that can be used for this conversion [4], namely pressure-retarded osmosis and reverse electrodialysis, and found that actually hardly attention was paid to the energetic efficiency. In the papers concerning reverse electrodialysis, for instance, we descried more-or-less founded estimates for the obtainable energy recovery ranging from 0.35 MJ per m3 of river water [5] to 0.6 MJ per m3 of river water [6]. These are not quite attractive numbers, especially not when the costs of pre-treatment are taken into account. From this point of view, the absence of experimental investigations regarding the obtainable energy recovery is a peculiar gap in the field of reverse electrodialysis. The aim of our study [7], therefore, was to investigate the energy recovery that can be obtained.

In our experimental setup, two batches of salt solutions with same volumes (550 mL each) were recycled over a reverse electrodialysis stack, namely 0.5 M NaCl (‘sea water’) and 0.005 M NaCl (‘river water’). The available work from mixing is then 0.80 kJ (i.e. 1.36 MJ per m3 of river water, which is considerably lower but more realistic then the mentioned 2.3 MJ). The mixing process was carried out at different current densities (5, 10&25 A/m2). During the mixing process, the stack voltage was measured. From this measurement, the energy yield can be calculated. For a reverse electrodialysis stack with 0.5 mm inter-membrane distance which was operated with a current density of 5 A/m2, the energy yield after complete mixing was 0.65 kJ (an energy recovery of 83%). Obviously, the energy recovery was lower at higher current densities.

Theoretically, the internal losses could be minimized by reducing the inter-membrane distance, especially from the compartments filled with the low-conducting river water. It was found, however, that a reduction of the compartment thickness from 0.5 mm to 0.2 mm resulted in an almost equal

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energy recovery. This is a remarkable result, and for this reason the losses were analyzed into more detail: firstly the losses due to non-ideality of the membranes and secondly the losses associated with charge transfer. It was supposed that besides the compartment thickness, also the geometry of the spacer affects the internal resistance.

In conclusion, this study shows that reverse electrodialysis is able to obtain a high energy recovery from mixing sea water and river water. The obtainable energy recovery is more than 80% which means an energy yield of >1.2 MJ per m3 of river water. From this study can also be concluded that in the development of reverse electrodialysis, special attention should be given to the development of the compartments between the membranes.

[1] J. N. Weinstein, F. B. Leitz, Electric-Power From Difference In Salinity - Dialytic Battery, Science 191 (4227) (1976) p557-559.

[2] G. L. Wick, W. R. Schmitt, Prospects For Renewable Energy From Sea, Marine Technology Society Journal 11 (5-6) (1977) p16-21.

[3] R. S. Norman, Water Salination: a Source of Energy, Science 186 (1974) p350-352.

[4] J. W. Post, J. Veerman, H. V. M. Hamelers, G. J. W. Euverink, S. J. Metz, D. C. Nymeijer, C. J. N. Buisman, Salinity-gradient power: Evaluation of pressure-retarded osmosis and reverse electrodialysis, Journal of Membrane Science 288 (2007) p218-230.

[5] C. Forgacs, Recent Developments In The Utilization Of Salinity Power, Desalination 40 (1-2) (1982) p191-195.

[6] J. Jagur-Grodzinski, R. Kramer, Novel Process For Direct Conversion Of Free-Energy Of Mixing Into Electric-Power, Industrial & Engineering Chemistry Process Design And Development 25 (2) (1986) p443-449.

[7] J. W. Post, H. V. M. Hamelers, C. J. N. Buisman, Energy recovery from controlled mixing salt and fresh water with a reverse electrodialysis system, Environ Science Technology (Submitted 2008-02-12)

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Hybrid and Novel Processes I – 6

Monday July 14, 5:00 PM-5:30 PM, Kaua’i

Electrocatalytic Membranes for Glucose/O2 Biofuel Cell.

M. Géraldine (Speaker), European Membrane Institute, France, T. Sophie, European Membrane Institute, France, [email protected] R. Marc, European Membrane Institute, France C. Marc, European Membrane Institute, France I. Christophe, European Membrane Institute, France

The constant increase in energy consumption in our modern society and the significant environmental impact involved in the use of non- renewable energy sources will shortly force us to find an alternative method of energy production. A fuel cell usually relies on hydrogen as carburant and oxygen as oxidant to generate power through the electrochemical conversion of fuels directly into electricity. Because electrical energy is generated without combustion, fuel cells are an extremely attractive option from an environmental standpoint. The incurred redox reactions generate electrons at the electrodes and consequently a voltage, accompanied by the production of water and heat. Biofuel cells use biocatalysts, to convert chemical energy into electrical energy at room temperature and under physiological conditions. The development of these systems focuses on the different methods of enzyme immobilisation and the establishment of their electrical connection to the electrodes. Efficient connection is achieved by the use of appropriate redox mediators which can shuttle electrons between the active site of the enzymes and the electrode surfaces. Surface-immobilized mediators and enzymes are the key factors to improving electron transfer at the electrode interface. Some approaches have been devised to construct a glucose/O2 biofuel cell by exploiting the oxidation of glucose coupled to the reduction of dissolved oxygen. Glucose is electrooxidized at the anode to gluconolactone by glucose oxidase and dioxygen is reduced to water at the cathode by specific enzymes such as laccase [1] The recent investigations in biofuel cells [2] are devoted to miniature and implantable cells that appear to be alternative methods of producing low power energy. This research field is currently under extensive development at an international level. The objective is the construction of a glucose/O2 biofuel cell, both efficient and stable. The application of this device is to generate electrical current to supply micro- machines, biosensors, or even implantable sources.

The originality of our work, compared to literature, concerns the structure and the porous nature of the electrodes. Carbon porous tubes were used as original conducting membrane support for enzyme incorporation and for transport of dissolved dioxygen solution via convective flow, through the porosity. This membrane allows the enzymatic reaction with dioxygen and the electrochemical

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reaction with mediator due to the conductivity of the support. Various enzyme immobilisation techniques on porous supports have been developed [3]. On the other hand, the elaboration of a matrix polymer based on polypyrrole obtained by electrochemistry is a manufacturing technique, well mastered in the IEM [4] to allow for producing stable conductive interfaces. At the cathode, oxygen is directly reduced to water by laccase or BOD and at the anode glucose is oxidised in gluconolactone by glucose oxidase, in the presence of their respective redox mediators 2,2-azinobis(3- ethylbenzothiazoline-6-sulfonate) and 8- hydroxyquinoline-5-sulfonic acid. The enzyme/mediator couples were immobilized by covalent linkage via an N-substituted polypyrrole matrix beforehand electrodeposited on carbon porous electrodes.

Experiments were conducted to determine the activity and the stability of the enzymes immobilized on the electrocatalytic membrane. Operational conditions and performances of the electrocatalytic membrane have been studied by electrochemistry. These electrochemical studies will be carried out in model conditions [5,6] in a physiological environment. The feasibility of each enzyme contactors was demonstrated by chronoamperometry and current voltage measurements using electrochemical halfs cells. Performances of the glucose/O2 biofuel cell were demonstrated by current voltage curves operating at variable external loads.

The electrocatalytic membrane presented good and stable current densities that established the feasibility of the co- immobilization of both enzyme and its mediator on the electropolymerized films and of an operative glucose/O2 biofuel cell.

1. G. Tayhas, R. Palmore, H.H. Kim, J. Electroanal. Chem. 1999, 464, 110

2. Kendall K., Nature Materials, 2002, 1, 211

3. G. Merle, L. Brunel, S. Tingry, M. Cretin, M. Rolland, K. Servat, C. Jolivalt, C. Innocent, P. Seta, Mat. Sci. Eng C. (in press)

4. A.Naji, C. Marzin, G. Tarrago, M. Cretin, C. Innocent, M. Persin, J. Sarrazin, J. Applied Electrochem. 31, 2001, 547-557

5. K. Servat, S. Tingry, L. Brunel, S. Querelle, M. Cretin, C. Innocent, C. Jolivalt and M. Rolland, J. Appl. Electrochem. 37, 23007, 121

6. L. Brunel, J. Denele, K. Servat, K.B. Kokoh, C. Jolivalt, C.Innocent, M Cretin, M. Rolland and S. Tingry, Electrochem. Comm. 9, 2007, 331

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Nanofiltration and Reverse Osmosis I - Membranes – 1 – Keynote

Monday July 14, 2:15 PM-3:00 PM, Maui

Development of Reverse Osmosis FT-30 Membranes with Polyethylene Oxide Brush Modified Antifouling Surface

J. Niu (Speaker), The Dow Chemical Company, Edina, MN, USA B. Mickols, The Dow Chemical Company, Edina, MN, USA, [email protected] J. Thorpe, The Dow Chemical Company, Edina, MN, USA A. Abaye, The Dow Chemical Company, Edina, MN, USA

Many applications that use membranes processes could benefit from a wide range of polymer chemistries that would resulting in better performance and be more chemically robust, low fouling, and less expense than current polymers. Breakthroughs in membrane robustness, in particular improved durability and cleanability would significantly reduce the cost of operation of reverse osmosis (RO)/nanofiltration (NF) water systems. This would extend the economic viability and growth of reverse osmosis technology. As a consequence, surface modification of our already widely used polymers become more and more important for the improvement of thin film composite membranes. We’ll show how we have designed specific polymers to surface modify FilmTec’s FT-30 membranes to improve operation in fouling waters (biofilm, oil and soap). The polymerization of poly(ethylene oxide) (PEO) brush from PEO methacrylate and a functional co-monomer (epoxy, maleic anlydride, etc.) using radicals or atom transfer in this synthesis is very well suited for making the crosslinkable macromolecules. Reacting these polymers with the surface of FT-30 membranes improved our ability to clean these membranes. These PEO brushes, which have a comb-like architecture, have proven to be very efficient in preventing both formation of biofilms and fouling from oil and soap. Such novel PEO based antifouling polymer may provide long-term control of surface fouling in the physiologic, marine and industrial environments. The synthetic diversity of these water-soluble polymers was explored to better understand the fundamental relationship between fouling resistance and polymer chemical composition.

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Nanofiltration and Reverse Osmosis I - Membranes – 2

Monday July 14, 3:00 PM-3:30 PM, Maui

Desalination Membranes Based on Directly Sulfonated Poly(arylene ether sulfone) Copolymers

H. Park (Speaker), University of Ulsan, Ulsan, Korea, [email protected] W. Xie, University of Texas at Austin, Austin, TX, USA B. Freeman, University of Texas at Austin, Austin, TX, USA M. Paul, Macromolecules and Interfaces Institute and Department of Chemistry, Blacksburg, VA, USA H. Lee, Macromolecules and Interfaces Institute and Department of Chemistry, Blacksburg, VA, USA J. Riffle, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA J. McGrath, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA

We have synthesized and characterized a systematic series of new sulfonated copolymer membranes, for use as desalination membranes, based on chemistry that is entirely different from the conventional post-polymerization sulfonation technique. Using direct copolymerization of sulfonated and other monomers, reproducible sulfonated copolymer membranes can be prepared as various polymer structures and compositions at different levels of sulfonation. This synthesis method overcomes the problems of conventional sulfonation technology such as molecular weight reduction during sulfonation. This study will discuss the preparation and evaluation of several families of sulfonated polymers such as random or segmented multiblock copolymers in terms of desalination characteristics (e.g., water permeability (or permeance), salt permeability and salt rejection). These sulfonated polymers or their thin-film composite membranes exhibit high tolerance to chlorine attack, which is in contrast to conventional desalination membranes such as those based on aromatic polyamides or cellulose acetate. They also exhibit high water flux and good salt rejection. To delineate structure-property relations for these materials, solubility and diffusivity of water and various salts were also evaluated for a series of sulfonated polymers. These intrinsic properties were compared with those of commonly used cellulose acetate and polyamide membranes. This fundamental and systematic study of structure-property relations regarding newly synthesized sulfonated copolymer membranes provides guidelines regarding material selection for new reverse osmosis membranes.

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Nanofiltration and Reverse Osmosis I - Membranes – 3

Monday July 14, 3:30 PM-4:00 PM, Maui

Structure-Property Relationships in PEG-Based Hydrogel Membrane Coatings

A. Sagle (Speaker), University of Texas at Austin H. Ju, University of Texas at Austin B. Freeman, University of Texas at Austin, [email protected] M. Sharma, University of Texas at Austin

The search for new water resources continues as demand for fresh water increases worldwide. One potential resource is produced water, a byproduct of oil and natural gas production, which is a complex emulsion composed of oil and other organics, salts, and particulate matter. Currently, 92% of produced water is reinjected, but cost-effective treatment could provide new water resources for beneficial uses in applications such as irrigation, power generation, and even human consumption.

Reverse osmosis (RO) membranes are a potential option to purify produced water because they are capable of removing up to 99.9% of monovalent salts as well as particulates and emulsified oil. However, RO membranes foul strongly in the presence of oily feed waters. One proposed solution to reduce membrane oil fouling is to apply a hydrophilic coating to the membrane surface. An ideal coating would be hydrophilic, resist oil droplet adhesion, and minimally impact the water flux and salt rejection of the underlying desalination membrane.

As a first step towards preparing fouling-resistant coatings for RO membranes, three series of copolymer hydrogel networks were synthesized using poly(ethylene glycol) diacrylate (PEGDA) as the crosslinker and acrylic acid (AA), 2-hydroxyethyl acrylate (HEA), or poly(ethylene glycol) acrylate (PEGA) as comonomers. Materials were prepared using varying amounts of PEGDA and comonomer. Glass transition temperatures in these materials obeyed the Fox equation. Both water and NaCl transport properties were studied, and ethylene oxide content and crosslink density influenced these transport properties. For example, the volume fraction of water sorbed by a 100 mole% PEGDA hydrogel was 0.61. However, introducing comonomers into the network reduced hydrogel crosslink density, and in hydrogels having the same ethylene oxide content, water sorption increased as crosslink density decreased. Water permeability increased systematically with increasing water sorption, and water permeability coefficients ranged from 10 - 26 L micron/(m2 hr bar). NaCl partition coefficients ranged from 0.36 to 0.53 (g NaCl/cm3 hydrogel)/(g NaCl/cm3 solution) and correlated strongly with water sorption. NaCl diffusion coefficients varied little with polymer composition; in this regard, diffusion coefficient values ranged from

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4.3x10-6 to 7.4x10-6 cm2/s. Based on contact angle measurements using n decane in water, oil exhibited a low affinity for the surfaces of these polymers.

Composite membranes using these materials and a commercial RO membrane as a substrate were prepared using spin coating. Initial studies show composite membrane behavior to follow trends predicted by a flux resistance model. The influence of the coating on salt rejection is also examined using a resistance model.

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Nanofiltration and Reverse Osmosis I - Membranes – 4

Monday July 14, 4:00 PM-4:30 PM, Maui

Engineering Molecular Weight Cut-Off of Organic Solvent Nanofiltration (OSN) Membranes for Natural Product Fractionation

I. Sereewatthanawut (Speaker), Membrane Extraction Technology Ltd, [email protected] Y. See Toh, Imperial College London F. Lim, Membrane Extraction Technology Ltd A. Boam, Membrane Extraction Technology Ltd A. Livingston, Imperial College London

In recent decades there has been an increase in consumers’ concerns over the quality and safety of many products including food, medicines and cosmetics. Consumer’s preference has strongly moved to products produced from natural sources as opposed to synthetic sources. As a result of this market demand, the production of natural products has rapidly expanded and become a global industry.

The production of natural products mainly involves separation processes. In general, the most challenging aspect of natural compounds production are the purification and fractionation steps. Current state-of-the-art technologies for separation and purification involve the use of either distillation technology (short-path or conventional distillation), or conventional preparative liquid chromatography. In recent years, membrane technology, particularly organic solvent nanofiltration (OSN), has attracted a great deal of attention as an alternative molecular separation technology. The main advantage of employing OSN for purification of natural extracts is that by selecting suitable molecular weight cut-off (MWCO) membranes, this technology can be used to fractionate molecules of similar molecular weight (e.g. in the 200 to 1000 Da range) at a much lower operating temperature compared to conventional processing operations. In addition to the large saving in energy costs, natural products are often susceptible to thermal damage and thus the milder operating conditions of a membrane process can minimize the nutritive value loss from thermal degradation.

The key aspect of employing this technology in natural product purification is therefore to tailor and control the MWCO of OSN membranes. This study reports the successful development of a robust technique for producing OSN membranes with tuneable molecular weight [1]. We have found that through careful control of the membrane formation conditions, it is possible to generate a family of membranes with MWCO in the nanofiltration range, i.e. 200 to 1000 Da. We have also shown that these membranes can be produced at pilot scale and used to form spiral wound elements.

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The development of these membranes and their application to natural products processing, including the Solvent Extraction Membrane Separation (SEMS) process [2] (in which different MWCO OSN membranes are used to fractionate free fatty acids from glycerides in natural oils), will be presented and discussed in this presentation.

[1] See Toh, Y H, et al., Engineering molecular weight cut off curves for highly solvent stable nanofiltration membranes, Journal of Membrane Science, manuscript submitted.

[2] International Patent No.WO/2008/002154.

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Nanofiltration and Reverse Osmosis I - Membranes – 5

Monday July 14, 4:30 PM-5:00 PM, Maui

High-Temperature Nanofiltration Using Porous Titania Membranes

T. Tsuru (Speaker), Hiroshima University, [email protected] K. Ogawa, Hiroshima University T. Yoshioka, Hiroshima University

Nanofiltration is conventionally operated at ambient temperatures for water treatment such as desalination and purification of land water. Rapid increase in membrane applications will expand the operation of nanofiltration at high temperatures such as water treatment in sugar industries and textile industries [1,

2]. However, polymeric nanofiltration membranes, which are mostly prepared from polyamide, can be used in a limited range of temperatures lower than 60 °C due to the glass transition [1]. On the other hand, ceramic membranes, especially titania membranes, show excellent thermal stability as well as chemical resistance, and can be used in both acidic and basic pHs [3, 4]. In this paper, nanoporous titania membranes with controlled pore sizes in the range of 1-3nm were successfully prepared by sol-gel processing, and the transport performance was evaluated in the temperature range from 30 to 90C.

Two types of titania sol solutions were prepared for the preparation of nanoporous membranes: colloidal and polymeric sols. In the polymeric sol route, hydrolysis and condensation reactions of titanium tetra-isoproxide (TTIP) were carried out with a small amount of water (molar ratio of H2O/Ti = 3~5) in isopropanol solutions [5]. On the other hand, in peptization method, an excess amount of water was added at the hydrolysis step at 60-70C for complete hydrolysis, resulting in milky aggregated sols. After adding an acid such as nitric acid, the milky sol was peptized to colloidal sol solutions, which were transparent and bluish. Sol sizes in both cases could be controlled by the molar ratio of the composition (acid concentration, water/Ti, etc.), temperature, aging time. Titania sols were coated on a-alumina capillary (pore size: 150 nm, outer diameter 3 mm, thickness 0.36mm) and fired at 350-650C.

Average pore sizes of TiO2 membranes determined by nanopermporometry [6] were successfully controlled from 2- 5 nm using colloidal sols and from 0.7-2 nm using polymeric sols, by controlling the sol preparation conditions (pH, temperature, concentration) and firing temperatures. TiO2 membranes showed molecular weight cut-offs (MWCO) of 500-2,000 and pure water permeability (Lp) of 10-11 to 10-10 m3m- 2s-1Pa-1.

With an increase in permeation temperatures from 30 to 90C, the water permeability increased 2-3 times depending on the pore sizes. Corrected water

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permeability, defined as water permeability multiplied by viscosity in bulk water, was not constant and increased with a decrease in pore sizes, that is, the water permeation mechanism was found to be different from the viscous flow. This is probably because water molecules, which are tightly bound to the hydrophilic surface of TiO2 membranes and were confirmed by measuring non-freezing and bound water in TiO2 powders, shows different temperature dependence from that in bulk.

Rejection of neutral solutes (raffinose, PEG1000) decreased with temperature in the range of 30-90 C, while that of electrolytes(MgCl2, NaCl) were approximately constant. Based on Spiegler-Kedem equation, reflection coefficients for both solutes were successfully fitted to be independent of permeation temperatures. Permeability coefficients (P) of electrolytes were found to show the same temperature dependence as Lp, that is, P increased almost linearly to Lp. On the other hand, P of neutral solutes showed larger temperature dependence than Lp, that is the neutral solutes were found to be transported in activated diffusion. The transport mechanism of neutral and electrolyte solutes, which are molecular sieving and charge effect, respectively, are found to be responsible for the temperature dependence.

[1] N. Amar, H. Saidani, A. Deratani, J. Palmeri, Langmuir, 23(2007) 2937.

[2] T. Tsuru, S. Izumi, T. Yoshioka, M. Asaeda, AIChE Journal, 46 (2000) 565-574.

[3] T. Tsuru, Separation and Purification Methods, 30 (2001) 191-220.

[4] T. Tsuru, J. Sol-Gel Sci., Tech., in press.

[5] T. Tsuru, D. Hironaka, T. Yoshioka, M. Asaeda, Sep. Purif. Tech., 25 (2001) 307-314.

[6] T. Tsuru, T. Hino, T. Yoshioka, M. Asaeda, J. Membr. Sci., 186 (2001) 257-265.

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Nanofiltration and Reverse Osmosis I - Membranes – 6

Monday July 14, 5:00 PM-5:30 PM, Maui

Polypyrrole Modified Solvent Resistant Nanofiltration Membranes

X. Li (Speaker), Centre for Surface Chemistry and Catalysis, Faculty of Bioscience Engineering, Leuven, Belgium P. Vandezande, Centre for Surface Chemistry and Catalysis, Faculty of Bioscience Engineering, Leuven, Belgium I. Vankelecom, Centre for Surface Chemistry and Catalysis, Faculty of Bioscience Engineering, Leuven, Belgium, [email protected]

Nanofiltration (NF) is a process in which feeds are separated over a membrane by means of pressures between 5 and 20 bars. Permeation takes place through the very small pores present in the membranes, or sometimes even through the available polymer free volume only.1 Large scale applications currently exist in waste water treatment and drinking water production. A major challenge these days is to broaden the range of NF- applications to organic feeds (SRNF).2-3 A more widespread use requires solvent-resistant membranes that preserve their separation characteristics under more aggressive conditions of strongly swelling solvents and elevated temperatures. Solvent stable polymers mostly contain aromatic structures and hardly possess functional groups. Since some affinity between membrane polymer and permeating solvent is needed, the few commercial SRNF-membranes currently available are limited to applications in apolar solvents. Moreover, being uncrosslinked, the existing polymeric membranes dissolve in aprotic solvents. Polypyrrole (PPy) is a chemically extremely resistant polymer, being insoluble in any organic solvent. Shaped as nanoparticles, it has received considerable attention in catalysis, chromatography, controlled drug release and pigment applications.4-5 Compared with conventional polymers, PPy has a high surface energy, as well as good electro-conductive and acid-base properties. In the membrane field, PPy based membranes have been already mentioned for in the gas separation and pervaporation but not for nanofiltration (NF) and solvent resistant nanofiltration (SRNF) applications. Most of PPy based membranes were prepared by interfacial polymerization. Pyrrole monomer vapour then first goes through the membranes and reaches the other side of membranes, which was contacted with oxidant and then polymerizes on the surface of the membranes. In the presented work, the special properties of PPy will be used to enhance the SRNF performance of membranes. Due to the poor solubility of PPy, an in-situ polymerization method was adopted to modify the existing membranes. In this method, the pyrrole monomer was first introduced on the surface of the membrane support, which was immersed in an oxidant solution to initiate the polymerization. The density of PPy can be controlled by the concentration of the pyrrole solution. To confirm the versatility of this method different membranes

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supports including charged (PSF/SPEEK, hydrolyzed PAN), none charged (PSF, PI) were modified by PPy.

The research showed that this method is versatile and simple method to prepare SRNF membranes. PPy modified membranes show a very high retention for negatively charged Rose Bengal in different solvents system, comparable to those of the MPF-50 and STARMEM 122 commercial membranes, but at a flux that is much higher. The extended filtration experiment with PPy modified membranes in DMF showed a stable permeability and retention over 30 hours.

References:

1. M. Mulder, Basic Principles of Membrane Technology, Kluwer Academic, Dordrecht, The Netherlands 1991, 89-140.

2. I. F. J. Vankelecom and L. E. M. Gevers Pressure- driven membrane processes Chapter in Green separation processes C.A.M. Afonso, J.G. Crespo (Eds), Wiley-VCH, Weinheim, Germany, 2005.

3. P. Vandezande, L. E. M. Gevers and I. F. J. Vankelecom, Chem. Soc. Rev. 2008, DOI: 10.1039/b610848m.

4. M. Yuasa, A. Yamaguchi, H. Itsuki, K. Tanaka, M. Yamamoto, and K. Oyaizu, Chem. Mater. 2005, 17, 4278.

5. X. T. Zhang, J. Zhang, Z. F. Liu and C. Robinson, Chem. Commun. 2004, 1852.

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Nanostructured Membranes I – 1 – Keynote

Monday July 14, 2:15 PM-3:00 PM, Moloka’i

Novel Polymers of Intrinsic Microporosity (PIMs): Towards An Understanding of Structure-Property Relationships.

N. McKeown (Speaker), Cardiff University, Cardiff, UK, [email protected] B. Ghanem, Cardiff University, Cardiff, UK K. Msayib, Cardiff University, Cardiff, UK P. Budd, Univesity of Manchester, Manchester, UK D. Fritsch, GKSS, Germany

Polymers of Intrinsic Microporosity (PIMs) are materials that combine the processability of polymers with a high degree of microporosity arising from their rigid and non-planar structures that cannot fill space efficiently [1]. The rigidity is enforced by the polymer backbone being composed solely of fused-rings and the necessary sites of contortion are typically provided by spiro-centres or triptycenes. PIMs can be prepared either as highly insoluble network polymers or as soluble polymers (e.g. PIM-1, Fig. 1a and b) that are suitable for the fabrication of self-standing films, submicron coatings or fibres a unique advantage over conventional microporous materials. Their unique combination of properties (microporosity, thermal stability, solubility and structural diversity) makes them attractive for several applications [2] but they are particularly promising as membrane materials. In particular, a number of published examples of PIMs[3] display gas permeability data that lie above the Robeson plot[4] for the separation of important gas pairs (e.g. O2/N2, CH4,CO2), showing that they have good selectivity as well as high permeability. This presentation will describe recent work at Cardiff that has the objective of preparing new PIMs to afford a better understanding of polymer structure-property relationships. These PIMs are derived from the chemical synthesis of novel monomers based on triptycenes, spiro-bisindane and hexaazatrinaphthylene subunits, which are designed to possess greater microporosity and/or binding sites for the inclusion of metals as catalysts or for facilitated transport across the membrane. Attempts will be made to correlate the structure of the PIM with the degree of microporosity achieved, as assessed by low temperature gas adsorption, and their gas permeabilities.

[1] P. M. Budd, B. S. Ghanem, S. Makhseed, N. B. McKeown, K. J. Msayib, C. E. Tattershall, Chemical Communications 2004, 230.

[2] A recent review on PIMs: N. B. McKeown, P. M. Budd, Chemical Society Reviews 2006, 35, 675.

[3] P. M. Budd, K. J. Msayib, C. E. Tattershall, B. S. Ghanem, K. J. Reynolds, N. B. McKeown, D. Fritsch, Journal of Membrane Science 2005, 251, 263.

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[4] L. M. Robeson, Journal of Membrane Science 1991, 62, 165.

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Nanostructured Membranes I – 2

Monday July 14, 3:00 PM-3:30 PM, Moloka’i

Physical Aging and Mixed-Gas Transport Properties of Microporous Polymers for Gas Separation Applications

S. Thomas (Speaker), Membrane Technology and Research, Inc., Menlo Park, CA, USA I. Pinnau, Membrane Technology and Research, Inc., Menlo Park, CA, USA, [email protected] M. Guiver, Institute for Chemical Process and Environmental Technology, National Research Council, Ottawa, Ontario, Canada N. Du, Institute for Chemical Process and Environmental Technology, National Research Council, Ottawa, Ontario, Canada J. Song, Institute for Chemical Process and Environmental Technology, National Research Council, Ottawa, Ontario, Canada

Membrane-based gas separation has been practiced as an economically viable separation technology during the past 30 years. Progress in this field resulted from significant improvements in materials science, development of high- performance membranes, and optimization in process design. Important applications include: a) nitrogen production from air, b) hydrogen recovery in petrochemical operations, c) removal of acid gases from natural gas, and d) recovery of condensable, high-value organic vapors from a variety of waste-gas streams. This presentation will focus on novel, intrinsically microporous glassy polymers, which may find applications in a wide variety of commercially important applications. The first generation of microporous glassy polymers was based on ultra-high free-volume glassy polyacetylene-based polymers, which exhibit the highest organic vapor/permanent gas selectivties coupled with the highest organic vapor permeabilities of all known polymers. However, a significant disadvantage of this class of materials is their inherent poor physical and chemical instability when operated under industrial conditions. Recently, Budd et al. reported that a new class of rigid, glassy ladder polymers, so called ‘polymers with intrinsic microporosity’ (PIM) may offer advantages over microporous polyacetylene-based polymers for membrane separations. This presentation will compare the transport properties of these two classes of microporous polymers for membrane separations. This study includes, for the first time, long-term gas permeability data of PIM-based materials. We studied the pure-gas permeation properties of PIM for over one year and the polymer’s properties are exceptional. The initial oxygen permeability dropped from 1,535 Barrer to 700 Barrer after one year of operation. On the other hand, the initial oxygen/nitrogen selectivity increased from 3.7 to 5.2. These are unmatched permeation properties for air separation, which lie far beyond the typical Robeson permeability/selectivity trade-off. In addition, PIM is stable in hydrocarbon environment with very high mixed-gas selectivity and permeability. For example, PIM-1 has a mixed- gas n-butane/hydrogen selectivity of 30-50 depending on the feed composition. In summary, microporous glassy polymers exhibit properties, which are unmatched

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by conventional polymers and provide a window to broaden possible applications for membranes used for gas separations.

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Nanostructured Membranes I – 3

Monday July 14, 3:30 PM-4:00 PM, Moloka’i

Polymers of Intrinsic Microporosity: New Copolymers, Syntheses, Properties and Applications.

D. Fritsch (Speaker), GKSS Research Centre Geesthacht GmbH, Germany, [email protected] K. Heinrich, GKSS Research Centre Geesthacht GmbH, Germany G. Bengtson, GKSS Research Centre Geesthacht GmbH, Germany J. Pohlmann, GKSS Research Centre Geesthacht GmbH, Germany

Since the discovery of polymers of intrinsic microporosity (PIM polymers) in 2004 [1] their superior properties and applicability in membrane separation processes were detected [2, 3]. Besides very recently reported polyimides based on the PIM concept [4] in this paper new copolymers of the PIM family with excellent film forming properties will be reported. As detected by modeling of PIM-1 [5] the site of contortion of the spirobisindane unit and the ether bonds attached to the dicyanobenzene are somewhat deformed in the packed model, thus showing more flexibility than expected. We concentrated our work on increasing the stiffness of the site of contortion by synthesizing new tetrahydroxymonomers and applying 2,3,5,6- tetrafluoro-4-cyanopyridine to introduce basic tertiary nitrogen to eventually shift the properties. The syntheses and basic gas data, such as permeability, diffusivity and solubility, will be reported for the first time. From these properties the microporosity of the new polymers may be presumed. To verify this hypothesis, a simple test applying PIM membranes for separation of methanol/Ar mixtures fitted to a mass spectrometer as detector was performed. Starting from gas/vapor-free thick membranes of about 100 µm, the pore filling process could be monitored by (1) fast increase of the argon signal according to the time-lag and (2) with increase of the methanol signal, accompanied by the methanol condensation in the micropores, a marked decrease of the argon signal was observed. This effect attributed to microporosity was validated further by measuring well known high free volume, microporous polymers of the polyacetylene family. In addition, thin-film composite membranes on different polymeric supports were prepared and the properties measured, including durability measurements for gases and in nanofiltration.

[1] P.M. Budd, B.S. Ghanem, S. Makhseed, N.B. McKeown, K.J. Msayib, C.E. Tattershall, Polymers of intrinsic microporosity (PIMs): robust, solution- processable, organic nanoporous materials, Chem. Commun., 2004, 230-231.

[2] P.M. Budd, E.S. Elabas, B.S. Ghanem, S. Makhseed, N.B. McKeown, K.J. Msayib, C.E. Tattershall and D. Wang, Solution- processed, organophilic membrane derived from a polymer of intrinsic microporosity , Adv. Mater., 2004, 16, 456-459.

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[3] P.M. Budd, K.J. Msayib, C.E. Tattershall, B.S. Ghanem, K.J. Reynolds, N.B. McKeown and D. Fritsch, Gas separation membranes from polymers of intrinsic microporosity, J. Membr. Sci., 2005, 251, 263-269.

[4] B.S. Ghanem, N.B. McKeown, P.M. Budd and D. Fritsch, Polymers of intrinsic microporosity (PIMs) derived from bis(phenazyl) monomers, Macromolecules, in print.

[5] M. Heuchel, D. Fritsch, P.M. Budd, N.B. McKeown, D. Hofmann, Atomistic packing model and free volume distribution of a polymer with intrinsic microporosity (PIM-1), J. Membr. Sci., in print.

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Nanostructured Membranes I – 4

Monday July 14, 4:00 PM-4:30 PM, Moloka’i

Characterizing the Pore Size distribution in Nanostructured Membranes

A. Hill (Speaker), CSIRO, Australia, [email protected]

Selective transport of small molecules through membranes is significantly influenced by the distribution of pore sizes not only at the surface but also throughout the bulk of the material. In the past few years with our collaborators, we have focussed on the development of methods of pore size manipulation, methods to measure pore size distribution (PSD), and methods to model and predict PSD. Underpinning our work are advanced characterisation tools for measuring internal and external porosity from 0.1 to 10 nm (positron spectroscopy), ~1 nm and above (small angle X-ray scattering) and from 10 to 100 nm (phase contrast X-ray imaging). This talk will cover examples of our work on tailoring and measuring pore size distribution in nanostructured membranes such as nanocomposites, polymers with intrinsic microporosity, molecular sieve silicas, and thermally rearranged polymers.

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Nanostructured Membranes I – 5

Monday July 14, 4:30 PM-5:00 PM, Moloka’i

Polymers of Intrinsic Microporosity in the Application of Organic Solvent Nanofiltration

K. Heinrich (Speaker), GKSS Research Centre Geesthacht GmbH, Germany D. Fritsch, GKSS Research Centre Geesthacht GmbH, Germany, [email protected] P. Merten, GKSS Research Centre Geesthacht GmbH, Germany G. Bengtson, GKSS Research Centre Geesthacht GmbH, Germany S. Dargel, GKSS Research Centre Geesthacht GmbH, Germany

Nanofiltration of aqueous solutions is a well developed method in industrial applications because it saves energy and costs. For non- aqueous, i.e., organic solvent nanofiltration (OSN) only a very few membranes are on the market available. Widely in use nanofiltration membranes for reverse osmosis are not stable against organic solvents. New kinds of polymers are the polymers of intrinsic microporosity (PIM polymers) [1] which shows superior properties concerning OSN. These are ladder-type poly(ether)s with a stiff backbone and a contorted structure that cannot pack closely and lead to a high free volume accompanied by a high surface area. They are only soluble in tetrahydrofurane and some halogenated solvents and are stable against many organic solvents without cross-linking. In this work composite membranes of PIM-1 and newly synthesized co-polymers were tested. The PIMs were prepared by polycondensation reaction from dicyanotetrafluorobenzene and tetrahydroxytetramethylspirobisindane [2]. Co- polymers were synthesized by analogous polycondensation with of a variety of new co- monomers. The synthesized polymers were characterized by size exclusion chromatography (SEC), NMR, IR, elemental analysis, density and permeability measurements. The fractional free volume was calculated from the density data. For preparation of composite membranes different membrane supports were applied, such as, poly(acrylonitrile) (PAN), cross-linked poly(acrylonitrile-co-glycidyl methacrylate) (PANGMA) and poly(vinyliden-fluoride) PVDF. Fillers were added to improve the nanostructered materials. Hexaphenylbenzene (HPB, MW = 534,71g/mol) was used as a model compound to test the retention in different solvents. The results show high fluxes in the range of 5 to 10 l/m²hbar and retentions up > 90%.

[1] Peter M. Budd et al., Adv. Mater. 2004, 16, 456.

[2] Kricheldorf et al., J. Polym. Sci. Part A.: Polym. Chem. 2006, 44, 5344 -5352.

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Nanostructured Membranes I – 6

Monday July 14, 5:00 PM-5:30 PM, Moloka’i

An Efficient Method for Preparing High Molecular Weight Polymers of Intrinsic Microporosity (PIM)s with Cyclic-Free Structure via Fast Polycondensation

N. Du (Speaker), Institute for Chemical Process and Environmental Technology, National Research Council, Ottawa, Ontario, Canada G. Robertson, Institute for Chemical Process and Environmental Technology, National Research Council, Ottawa, Ontario, Canada J. Song, Institute for Chemical Process and Environmental Technology, National Research Council, Ottawa, Ontario, Canada S. Thomas, Membrane Technology and Research, Menlo Park, CA, USA I. Pinnau, Membrane Technology and Research, Menlo Park, CA, USA M. Guiver, Institute for Chemical Process and Environmental Technology, National Research Council, Ottawa, Ontario, Canada, [email protected]

Recently, a British research group, reported on the syntheses of a number of wholly aromatic glassy ladder polymers, referred to as Polymers of Intrinsic Microporosity (PIM)s, via irreversible polycondensations at 65°C for 72 h. These polymers have attracted great interest as an outstanding class of advanced polymeric materials for membrane-based gas separation due to their rigid and contorted zig-zag chain structure and loose chain packing that is capable of generating very high free volume. In our work, a successful synthetic approach to high molecular weight linear ladder polymers with few low molecular weight cyclic species was carried out at elevated temperature and high monomer concentration. In contrast with previously reported conditions for preparing these PIM materials, the reaction could be completed within a few minutes. The polymer properties were characterized by GPC, 1HNMR, 13CNMR, FNMR, FT-IR, and MALDI-TOF MS. This procedure can also be used for the general synthesis of other ladder polymers by irreversible polycondensation of tetraphenols with activated tetrafluoro aromatics. Gas permeability coefficients (P) were measured for helium, hydrogen, carbon dioxide, oxygen, methane and nitrogen. PIM-1 exhibits high gas permeability coupled with moderate selectivity. For example, the oxygen permeability of PIM-1, made by the new synthetic method, is 1,650 Barrer coupled with an oxygen/nitrogen selectivity of 3.3.

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Fuel Cells I – 1

Monday July 14, 2:15 PM-3:00 PM, Honolulu/Kahuku

Polyoxadiazole Nanocomposite Fuel Cell membranes operating above 100°C

D. Gomes, GKSS Research Centre Geesthacht GmbH, Germany S. Nunes (Speaker), GKSS Research Centre Geesthacht GmbH, Germany, [email protected]

Among the high temperature polymer electrolyte membranes that have been developed so far, phosphoric acid doped polybenzimidazole [1], which contains amphoteric nitrogen groups, is certainly the most investigated system with high proton conductivity. Here, for the first time the use of a fluorinated polyoxadiazole doped with phosphoric acid as a proton-conducting membrane is reported for fuel cell operation at temperatures above 100 °C and low humidities. An advantage of polyoxadiazoles in comparison to the polybenzimidazoles is the lower reaction temperature (and time) required for synthesis [2]. The fluorinated polymer is very stable even in mixtures of sulfuric acid and oleum (20-65 % SO3) [3].

Protonated polyoxadiazole membranes with a doping level much lower than that usually applied for polybenzimidazole (0.34 mol of phosphoric acid per polyoxadiazole unit, 11.6 wt.% H3PO4) had proton conductivity at 120°C and RH=100% in the order of magnitude of 10-2 S cm-1. When experiments are conducted at low external humidity (relative humidity of 1%), still a high value of proton conductivity (6 x 10-3 S cm-1) was obtained at 150°C. Higher phosphoric acid doping levels were possible with the incorporation of sulfonated silica containing oligomeric fluorinated oxadiazole segments [4]. The functionalized silica has thermal stability up to 160 °C. With the addition of functionalized silica not only doping level but also water uptake increased. For the nanocomposite membranes prepared with the functionalized silica, higher proton conductivity in all range of temperatures up to 120°C and RH=100% (in the order of magnitude of 10-3 S cm-1) was observed when compared to the plain membrane (in the order of magnitude of 10-5 S cm-1).

[1] Q. Li, R. He, J.O. Jensen, d N.J. Bjerrum, Chem. Mater., 15 (2003) 4896-4915.

[2] D. Gomes, C. Borges, J.C. Pinto, Polymer, 45 (2004) 4997-5004.

[3]D. Gomes, S.P. Nunes, Journal of Membrane Science, in press (http://dx.doi.org/10.1016/j.memsci.2007.11.041).

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[4] D. Gomes, I. Buder, S.P. Nunes, Journal of Polymer Science Part B: Polymer Physics 44 (2006) 2278-2298.

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Fuel Cells I – 2

Monday July 14, 3:00 PM-3:30 PM, Honolulu/Kahuku

Nanocomposite Membranes with Low Methanol Permeability for the Direct Methanol Fuel Cell

B. Ladewig (Speaker), The University of Queensland, Australia, [email protected] D. Martin, The University of Queensland, Australia J. Diniz da Costa, The University of Queensland, Australia M. Lu, The University of Queensland, Australia

Current perfluorinated polymer membranes for the direct methanol fuel cell allow an unacceptably high level of methanol crossover from the anode to the cathode during operation, leading to decreased cell potential, fuel utilization efficiency and power output. It is therefore desirable to develop a new class of membrane materials with low methanol permeability, while maintaining high proton conductivity, and chemical, thermal and mechanical stability.

A range of silicon alkoxide precursors have been used with in-situ sol gel synthesis to prepare nanocomposite Nafion 117/inorganic membranes. The resulting nanocomposite membrane transport properties show a very strong dependence on the surface chemistry of the incorporated nanoparticles. In particular, using 3-mercaptopropyl trimethoxysilane as a precursor leads to a six-fold reduction in the methanol permeability, albeit with a slight decrease in proton conductivity.

Future directions for the development of robust DMFC membranes in our centre will be discussed with respect to current developments in the field.

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Fuel Cells I – 3

Monday July 14, 3:30 PM-4:00 PM, Honolulu/Kahuku

Proton Conducting Graft Copolymer Electrolyte Membranes for Fuel Cells

J. Koh, Yonsei University, Seoul, Korea J. Park, Yonsei University, Seoul, Korea D. Roh, Yonsei University, Seoul, Korea J. Kim (Speaker), Yonsei University, Seoul, Korea, [email protected]

A series of proton conducting comb copolymer membranes consisting of poly(vinylidene fluoride- co-chlorotrifluoroethylene) backbone and poly (styrene sulfonic acid) side chains, i.e. P(VDF- co-CTFE)-g-PSSA were synthesized using atom transfer radical polymerization (ATRP). 1H NMR, FT-IR spectroscopy, wide angle X-ray scattering (WAXS) and transmission electron microscopy (TEM) results present the successful ‘grafting from’ method using ATRP and the well-defined microphase-separated structure of the polymer electrolyte membranes. All the properties of ion exchange capacity (IEC), water uptake and proton conductivity for the membranes continuously increased with increasing PSSA contents. The results of thermal gravimetric analysis (TGA) also showed that all the membranes were stable up to 300 oC. After terminated chlorine atoms were converted to end-functional azide groups (P (VDF-co-CTFE)-g-PSSA-N3), the polymer electrolyte membranes were crosslinked under UV irradiation. The crosslinked P(VDF-co-CTFE)-g- PSSA membrane with 73 wt% of PSSA content exhibited the reduced water uptake from 300 to 83 %, the increased tensile strength from 21.1 to 26.2 MPa and the slightly reduced proton conductivity from 0.074 to 0.068 S/cm at room temperature compared to the uncrosslinked membrane.

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Fuel Cells I – 4

Monday July 14, 4:00 PM-4:30 PM, Honolulu/Kahuku

Nanocomposite Proton Exchange Membranes for Hydrogen Fuel Cells: Self-humidification, Molecular Nucleation and Dynamic Simulation

W. Zhang (Speaker), Hong Kong University of Science and Technology, Hong Kong, China P. Gao, Hong Kong University of Science and Technology, Hong Kong, China

Nafion membranes, consisting of a polytetrafluoroethylene (PTFE) backbone with sulfonic acid groups substituted at intervals along the chain, are the most widely used proton exchange membrane (PEM) materials for hydrogen fuel cell batteries. Their major drawback, however, is their inability to conduct protons at low water content levels. Both the external humidifier and physical seal of the fixture in commercial products increase the cost and complexity of the whole system. Therefore, we have developed a novel Pt-clay/Nafion nanocomposite membrane with significantly enhanced proton conductivity than the pristine Nafion membranes. Monolayers of Pt nanoparticles of diameters of 2-3 nm with a high crystallinity were successfully anchored onto exfoliated nanoclay surfaces using a novel chemical vapor deposition process. Chemical bonding of Pt to the oxygen on the clay surface ensured the stability of the Pt nanoparticles, and hence, no leaching of Pt particles was observed after a prolonged ultrasonication and a rigorous mechanical agitation of Pt-clay in the Nafion solution during the membrane casting process. Systematic analysis using WAXD and TEM showed that the recasting process produced a new self- humidifying exfoliated Pt-clay/Nafion nanocomposite membrane with a high crystallinity and proton conductivity. In situ water production for humidification of the dry membranes without any external humidification was characterized by a combined water uptake and FTIR analysis of the as-prepared membrane after a single cell testing without using electrodes. The power density at 0.5 V of a single cell made of a Pt-clay/Nafion nanocomposite membrane was 723 mW/cm2, which is 170 % higher than that made of a commercial Nafion 112 membrane of similar thickness.

Durability is another major obstacle for the PEM fuel cell commercialization as the membrane is the most fragile component. Hydrophobic PTFE backbones of Nafion membranes were believed to aggregate and form the crystallites inside the matrix. These crystallites, acting as physical crosslinks, are crucial for the mechanical and thermal robustness. However their size has been estimated to range between 3 to 5 nm, which is much smaller than the traditional nucleation agents. (eg. SiO2, CaCO3, TiO2 et al.) Thus, an aromatic molecule (3, 4-dimethylbenzaldehyde) was selected as the nucleation agent for these special nano-crystallites in Nafion. In this study, molecular dynamic simulation was firstly carried out using the Discover and Amorphous Cell modules of Materials Studio,

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which was developed by Accelrys Software Inc. The motivation for conducting an atomistic model for Nafion membranes was to investigate the effects of the nucleation agent on the dynamic behaviors of the backbones of Nafion in the casting process at the atomistic level. Simulation results shown that the backbones of Nafion with the presence of the nucleation agent were clearly found to be energetic at the temperature above Tg whereas be confined tightly at room temperature. Given that the activation and frozen phenomena were greatly alleviated in the model for the pristine Nafion, these tiny aromatic molecules were supposed to be self- assemble among the PTFE backbones of Nafion, promote their aggregation and consequently facilitate the crystallization. Accordingly, this nucleation agent was introduced into Nafion solution to cast membrane in the experimental investigation. The crystallinity of recast Nafion membrane with 3 wt% 3, 4- dimethylbenzaldehyde impregnated was estimated to be 26 % using WAXD, which ranges between 5 to 20 % for the commercial Nafion membranes at equivalent weight of 1100.

The project was sponsored by the Research Grant Council of Hong Kong with an earmarked grant for research, grant no. 612805.

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Fuel Cells I – 5

Monday July 14, 4:30 PM-5:00 PM, Honolulu/Kahuku

Sulfonated Polyimide Membranes for Polymer Electrolyte Fuel Cells

K. Okamoto (Speaker), Yamaguchi University, Ube, Yamaguchi, Japan, [email protected] K. Matsuda, Yamaguchi University, Ube, Yamaguchi, Japan Z. Hu, Yamaguchi University, Ube, Yamaguchi, Japan K. Chen, Yamaguchi University, Ube, Yamaguchi, Japan N. Endo, Yamaguchi University, Ube, Yamaguchi, Japan M. Higa, Yamaguchi University, Ube, Yamaguchi, Japan

Polymer electrolyte membrane (PEM) is the key component of polymer electrolyte fuel cell (PEFC). Many sulfonated hydrocarbon polymer membranes have been developed as alternatives for sulfonated perfluoropolymer membranes. Sulfonated polyimides (SPIs) are one of the promising candidates for PEMs because of their low fuel permeation, good film-forming ability and excellent mechanical, thermal and chemical properties. However, they have a disadvantage of rather easy hydrolysis of imide ring. We investigated the relationship between the chemical structure of SPIs and the water stability of their membranes, and developed SPI membranes with reasonably high water stability and high PEFC performance. In this presentation, we report on preparation of novel sulfonated polyimide membranes with excellent water stability and their applications for PEFCs.

SPIs bearing sulfophenoxy side groups were successfully prepared from 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTDA), 2,2-bis(4-sulfophenoxy)benzidine (2,2-BSPOB) and a non-sulfonated diamine such as 4,4-bis(4-aminophenoxy)biphenyl. The dry SPI membranes in proton form were immersed into the medium of phosphorous pentoxide/methanesulfonic acid to form cross-linking. Their uncross-linked and cross-linked membranes were evaluated as polymer electrolyte membranes for polymer PEFCs.

They maintained high mechanical strength and high proton conductivity after aging in water at 130 °C for 500 h, indicating their high water stability. PEFCs with the SPI membranes showed high performances at 90 °C and 0.3 MPa with air supply; for example, a cell voltage of 0.67 V at 0.5 A/cm2 under 85 %RH. They also showed fairly high performances even at a low humidity of 30%RH due to the back diffusion of water formed at the cathode, for example, a cell voltage of 0.63 V at 0.5 A/cm2. PEFCs with the cross-linked SPI membranes were operated under a constant current density of 0.5 A/cm2 at 90 °C and 85 %RH for 1600 h without any reduction in cell performance, indicating their high fuel cell durability. The SPI membranes have high potential for PEFCs at higher temperatures above 80 °C.

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Fuel Cells I – 6

Monday July 14, 5:00 PM-5:30 PM, Honolulu/Kahuku

Syntheses and Physical Properties of Novel Polymer Electrolyte Membranes Comprising Poly(diphenylacetylene)s

H. Ito (Speaker), EBARA Research Co. Ltd., Kanagawa, Japan, [email protected] R. Yamamoto, EBARA Research Co. Ltd., Kanagawa, Japan E. Akiyama, EBARA Research Co. Ltd., Kanagawa, Japan K. Takeda, EBARA Research Co. Ltd., Kanagawa, Japan H. Yokota, EBARA Research Co. Ltd., Kanagawa, Japan Y. Nagase, School of Engineering, Tokai University, Kanagawa, Japan

The fuel cell, particularly, proton exchange membrane fuel cell (PEMFC) is a promising technology to reduce dependence on petroleum oil and decrease emission of carbon dioxide and to actualize a hydrogen-based energy economy. The large part of the developing systems uses a perfluorinated ionomer, such as Nafion, as a proton exchange membrane. In present, Nafion and perfluorinated polymers have an advantage in durability compared with non-fluorinated polymers. However, these perfluorinated polymers exhibited low glass transition temperatures at around 393 K. Therefore, the operating temperature of a PEMFC system is restricted at 333-353 K. If a new polymer electrolyte which can be used at high temperature is available, the operating temperature of the system can be raised. As a result, a tank of hot water can be downsized and an oxidation process of carbon monoxide can be simplified. These simplifications will contribute to the cost reduction of the PEMFC system. Therefore, the development of a low-cost polymer electrolyte operational at high temperature is expected. On the other hand, numerous hydrocarbon ionomers have been studied for a proton exchange membrane. Generally speaking, the hydrocarbon ionomers synthesized in the past contained aromatic groups in their polymer main-chain in order to reinforce durability for oxidation. Especially, the wholly aromatic polymers, such as poly(phenylene), poly(arylene ether) and poly (aryl ether ether ketone) are studied energetically. However, the processability, particularly, film formation property of these polymers is not enough for practical use. We have much attention on poly (diphenylacetylene)s (PDAs) for a novel polymer electrolyte because of their good film formation property. In addition, this polymer has no hydrogen in its polymer main-chain; therefore, a hydrogen abstraction reaction which caused the degradation of the proton exchange membranes must not occur. On the other hand, these polymers have been known as one of the highest gas permeability synthetic polymers. This high gas permeability is undesirable for a proton exchange membrane because the gas cross over of hydrogen or oxygen will occur in a fuel cell. In addition, if the double bonds in the polymer main-chain show high reactivity, this polymer might be decomposed by hydrogen, oxygen and other gases during the operation. Therefore, the chemical stability for oxidation or reduction of the PDAs were

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investigated at first. As a result, it was suggested that these polymers are stable at both of oxidative and reductive conditions. Then, we synthesized sulfonated PDAs by soaking a membrane of PDA with trimethylsilyl groups in sulfuric acid/ethyl acetate solution. The physical properties such as gas permeability coefficients, ion-exchange capacity and tensile strength were investigated with these membranes. As a result, membranes of the sulfonated PDAs exhibited lower gas permeability compared with those of non-sulfonated PDAs, and oxygen gas permeability coefficient of the sulfonated PDA membranes were around 1.0 x 10-8 barrer. This gas permeability coefficient was as same as that of Nafion 115. This result indicated that the introduction of the sulfonic acid groups reduced the gas permeability. The sulfonated membranes showed good proton conductivity, 1.0 x 10-2 S/cm at 363 K, 90 % RH. Then, single cell performance was measured at 353 K, 90 %RH, and almost same performance was obtained compared with that of Nafion 115. The degradation ratio of the cell voltage was also estimated by holding at OCV condition for several hundred hours as the accelerating durability test. The average degradation ratio was about -150 uV/h. From these results, this novel proton exchange membrane comprising the PDAs will be candidate for the membrane to actualize high temperature operating of PEMFCs.

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Desalination I – 1 – Keynote

Monday July 14, 2:15 PM-3:00 PM, O’ahu

Energy Cost Optimization in RO Desalting and the Thermodynamic Restriction

R. Zhu (Speaker), University of California, Los Angeles, Los Angeles, CA, USA P. Christofides, University of California, Los Angeles, Los Angeles, CA, USA Y. Cohen, University of California, Los Angeles, Los Angeles, CA, USA, [email protected]

Modern RO and NF membranes can be operated at remarkably low pressures. However, these pressures are still significantly above the thermodynamic osmotic pressure. Although various studies have advanced a variety of approaches to evaluate the energy cost of reverse osmosis membrane desalination, such studies have not offered a simple mathematical formalism that considered the effect of the lower bound on the feed pressure on energy cost optimization. In the present study, a rigorous theoretical formalism was developed that clarifies the thermodynamic restriction on RO energy cost and provides a basis for RO process optimization. The present approach enables direct analytical solution for the minimum specific energy cost with respect to water recovery, feed and permeate flow rate. The additional impact of pressure drop within the membrane module, energy recovery devices, membrane hydraulic permeability and brine disposal cost were incorporated into the theoretical model. Specific results will be presented for simple RO configurations to demonstrate the impact of multi-stage RO operation on energy efficiency in relation to membrane cost. In addition, an analytical approach was developed to enable optimization, with respect to energy efficiency, for multi-pass RO and NF membrane desalting. The implications of the present work to lowering RO desalination cost by optimization of process configuration will be presented with reference to specific recently developed large-scale process configurations.

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Desalination I – 2 Monday July 14, 3:00 PM-3:30 PM, O’ahu

Characterizing RO Membrane Performance when Desalinating High pH Produced Water from the Oil Extraction Process

R. Franks (Speaker), Hydranautics, Oceanside, CA, USA, [email protected] C. Bartels, Hydranautics, Oceanside, CA, USA

Produced water is water brought to the surface as part of a high temperature oil and gas extraction process. Produced water can range in salinity and composition depending on its original source, but due to the nature of the produced water, the subsequent treatment steps, particularly the desalination of the produced water by reverse osmosis, faces unique challenges not encountered in the treatment of typical surface or well waters. For this reason, an improved understanding of the effect produced water has on RO membrane performance is required. The purpose of this study is to characterize the water transport, salt transport, and longevity of an RO membrane for the treatment of produced water.

The typical method for dealing with produced water is deep well injection. But oil production is limited by the well’s capacity to receive the produced water. For this reason, a combination of technologies is used to treat produced water for environmental, industrial, and agricultural reuse. Among these technologies is desalination by reverse osmosis. Specifically, reverse osmosis membranes are used in the final treatment step after oil, grease, solids and hardness removal and pH elevation. The RO step is designed to remove the remaining dissolved salts and organics, including sodium, silica and boron.

Due to the nature of the oil extraction process, produced water contains a unique mixture of dissolved salts and organics. The passage of salt through the RO membrane treating produced water at an elevated pH is distinctive from the common RO performance of many municipal and industrial applications operating at a neutral pH. A better understanding of salt passage is achieved by comparing the performance of membranes treating produced water with their performance on more typical feed waters and synthetic waters.

To do this, a review of the theories governing salt passage is first considered, including the variation in salt passage with increasing pH. The salt transport theories, along with years of accumulated data from RO systems treating more common feeds, are used to predict ion passage in a produced water system.

To compare theoretical and actual performance, samples from an RO membrane treating produced water in the field were analyzed. The analysis considered

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specific ions such as chloride, sodium, silica, and boron as well as the passage of organics by analyzing TOC. An analysis of the water transport coefficient was also conducted. In general, the membrane performed as expected. The water transport coefficient was found to be accurate and the salt passage of most ions supported the theoretical results. However, the passage of sodium was found to be significantly higher than the projected passage. The permeate pH also failed to conform to theoretical predictions. Instead of seeing a decrease in permeate pH relative to feed pH as is typical in RO systems operating at neutral pH, the permeate pH was found to increase relative to the high feed pH.

Additional controlled studies were conducted in the lab in an effort to better understand the differences between theoretical and actual performance. The studies were conducted on synthetic waters, typical surface waters, and produced water collected from the field. The passage of ions associated with the different mixtures, including sodium passage, was analyzed at different pH levels.

In addition of understanding salt passage when treating produced water, a better understanding of membrane longevity is necessary considering the high pH and high temperature operation associated with some produced water treatment processes. Operation at high pH can mitigate organic fouling of the RO and act as a kind of continuous cleaning. But exposure to high pH can also adversely affect the integrity of the membrane. Both the polyamide layer and the membrane’s polyester backing can be degraded by a combination of high temperatures and high pH. For this reason, the polyester backing, RO membrane, and RO elements were exposed to high pH solutions for extended periods. Strength testing was performed on the backing material and wet testing was done at one month intervals to quantify the increase in salt passage and the change in water permeability.

The theoretical data, field analysis, and laboratory tests compiled in this study will be used to better predict specific ion passage at high pH on both typical waters and on produced waters. The results of this study will also be used to better understand the long term behavior of an RO membrane when treating produced water.

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Desalination I – 3

Monday July 14, 3:30 PM-4:00 PM, O’ahu

Submerged Hollow Fibre Pre-treatment to RO in Seawater Applications

Y. Ye (Speaker), UNESCO Center for Membrane Science and Technology, School of Chemical Science, Sydney, Australia L. Sim, UNESCO Center for Membrane Science and Technology, School of Chemical Science, Sydney, Australia V. Chen, UNESCO Center for Membrane Science and Technology, School of Chemical Science, Sydney, Australia, [email protected] A. Fane, UNESCO Center for Membrane Science and Technology, School of Chemical Science, Sydney, Australia

Since reverse osmosis membranes are very sensitive to foulants such as colloids, inorganic scale and biofouling, proper pre-treatment process therefore becomes a critical factor for a successful long-run seawater reverse osmosis (SWRO) plants. Recently, low pressure membrane has been successfully used in the pre-treatment for wastewater reclamation by reverse osmosis (RO). This is because membrane pre-treatment offers several advantages such as smaller plant footprint, better quality of feed water for RO unit and less chemical consumption. As a result, the use of low pressure membrane is now being considered as a viable solution for pre-treatment to SWRO plants but further improvements in membrane configurations and operations need to be investigated to reduce fouling and energy consumption.

The aim of this study is to investigate the efficiency of pre-treatment using MF and UF submerged hollow fibre system by varying the operation parameters. Three different type of hollow fibre (0.22um polypropylene (PP) membrane and two 0.04um polyvinylidene fluoride (PVDF) membranes with different fibre outer diameters) were used for the pre-treatment of the synthetic seawater. Three different modes of filtration: continuous, relaxation and backwash mode of filtration were investigated. For all three membranes used, it was found that, during the relaxation mode of filtration, TMP only decreased slightly after 40s of relaxation in each filtration circle (1hr). The decrease of TMP was also observed after each backwash (3560s filtration, 40s backwash where the backwash flux is twice of the permeate flux). However, the rate of TMP increase during each filtration circle for the backwash mode is much higher than that in the relaxation mode of filtration. Consequently, it leads to higher final TMP value in the end of 20 hr’s backwash mode filtration when compared to the relaxation mode. Meanwhile, comparing different membranes fibres, it appears that bigger pore size PP hollow fibre has higher dTMP/dt in each cycle of filtration after backwash than those observed for smaller pore size PVDF membranes. All these indicate that inappropriate backwash might even accelerate the membrane fouling. The further characterization of the membranes using different mode of filtration is

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being carried out. In addition, the parameters of backwash/ relaxation such as filtration time, backwash/relaxation time and backwash strength are investigated to optimize the filtration performance.

Acknowledgements

The authors acknowledge the financial support of Department of Education, Science and Training, Australia via the International Linkage program. The project is collaboration with the European Union 6th Framework project, Membrane-Based Desalination: An Integrated Approach (MEDINA). The authors also acknowledge Memcor Australia Pty. Ltd. for membrane supply.

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Desalination I – 4

Monday July 14, 4:00 PM-4:30 PM, O’ahu

RO Membrane Desalting in a Feed Flow Reversal Mode

M. Uchymiak (Speaker), University of California, Los Angels B. Alex, University of California, Los Angeles P. Christofides, University of California, Los Angeles N. Daltrophe, Ben-Gurion University, Beer Sheva, Israel M. Weissman, Ben-Gurion University, Beer Sheva, Israel J. Gilron, Ben-Gurion University, Beer Sheva, Israel R. Rallo, Universitat Rovira i Virgili, Tarragona, Catalunya, Spain Y. Cohen, University of Calironia, Los Angeles, [email protected]

The growing demand for potable water, coupled with increasing salinity levels of traditional water sources, has led to a fast growth of membrane RO desalination as a potential solution to upgrading the quality of water supplies, as well as a solution for exploiting underutilized non-traditional water sources, especially brackish groundwater. However, product water recovery is often limited for inland water desalination due to membrane scaling by sparingly soluble mineral salts (e.g., calcium sulfate, calcium carbonate, barium sulfate) as well as silica.

Several methods are currently used to prevent scale formation; addition of antiscalant chemicals to the feed or flushing the membrane units with low-TDS (total dissolved solids) permeate water are two common procedures to accomplish this task. These current methods of scale mitigation have several disadvantages, antiscalants add to the cost of desalination, and the addition of excess amounts can encourage membrane biofouling and even promote scaling in some cases. In the case of permeate flush, the reverse osmosis operation must be halted to allow for the flushing cycle, thereby reducing permeate production, and using valuable permeate water. In the preset work, an automated novel technique of feed flow reversal has been developed, which can prevent mineral scaling without the addition of expensive chemicals or periods of system downtime. In the present process configuration, a system of electronically actuated valves is configured specifically to enable periodic reversal of the feed flow direction through the RO modules. This reversal of the feed flow also reverses the axial salt concentration profile at the surface of the membrane, effectively "resetting the crystallization induction clock. The feed flow reversal, when activated just after the first crystals have formed, also allows a substantial portion of scale deposited on the membrane surface to re-dissolve into solution.

In order to automate the flow-reversal mode of operation, a novel ex-situ scale observation detector (EXSOD) system was developed with the hardware and software to allow for direct monitoring of the onset of scaling in RO processes. The EXSOD system was coupled with model-predictive control algorithms that

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were developed to enable feed-flow reversal operation. Open-loop and closed-loop simulations demonstrated non-linear model-predictive control strategies that transition from the high-flow to low-flow steady-states in an optimal way while subjected to plant-model mismatch on the feed concentration, actuator constraints, and sampled measurements. The EXSOD detection of scale is based on direct surface imaging, whereby the appearance of surface crystals is analyzed in real-time using novel image analysis algorithms. Upon the detection to the onset of surface scaling, a control signal is sent to the RO plant PLC to initiate flow reversal. The flow reversal approached was successfully demonstrated in both laboratory bench-scale studies and in RO pilot plant studies demonstrating the ability to maintain constant permeate flux, without the use of antiscalants, even under conditions of supersaturation. The study has the demonstrated that the cost of water desalination can be reduced, whenever there is propensity for mineral scaling, by using the feed flow reversal approach, both due to eliminating the need for antiscalants and expected reduction in the frequency of membrane cleaning.

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Desalination I – 5

Monday July 14, 4:30 PM-5:00 PM, O’ahu

Evaluating the Performance of Single-Pass RO and Multi-Pass NF/RO Systems for Seawater Desalination

D. Tanuwidjaja (Speaker), University of California, Los Angeles, Los Angeles, CA, USA, , [email protected] E. Hoek, UCLA CEE Dept/CNSI/WaTeR Center, Los Angeles, CA, USA

In recent years, reverse osmosis (RO) seawater (SW) desalination technology has undergone a remarkable transformation. The number and capacity of large SWRO plants and pilot facilities have increased significantly. An emerging approach to seawater desalination is the use of complex, integrated multi-stage and multi-pass systems [1]. Energy required to drive conventional single-pass SWRO process comprises ~40 percent of the total cost of water produced. The RO product water recovery cannot be driven beyond about 50-60 percent because increasing retentate osmotic pressure at high recovery produces a diminishing economic benefit. In addition, the higher retentate concentration increases salt passage, as well as fouling and scaling concerns. Two novel approaches to reduce energy consumption in seawater desalination include: (1) the use of seawater RO membranes with different permeability to balance flux and pressure through the system (e.g., the ‘Dow-FimTec’ method [2]) and (2) the use of a two-pass seawater nanofiltration (NF) membrane system (e.g., the ‘Long Beach’ method [3]).

We hypothesize that nanofiltration of seawater (using conventional NF membranes) could dramatically reduce the fouling and scaling potential of the feed, and the foulant-free seawater desalted by RO membranes operating at much higher flux and recovery without significantly increasing specific energy consumption; thus, reducing the overall cost of water produced. Additional benefits of NF pretreatment include the fact that NF membranes are relatively stable against chlorine attack allowing for better bio-growth control, plus NF membranes almost completely reject dissolved organic matter, which may be a critical foulant during algal blooms. Further, the RO process can be operated at high pH due to reduced scaling concerns, which should enhance boron rejection. Finally, NF pre-treatment creates options for NF concentrate demineralization and recycling back to the plant feed, further increasing recovery and reducing brine discharge.

Objectives of this study are: (1) create a model to assess product water quality and specific energy consumption in single-pass and multi-pass NF/RO systems, (2) determine the optimal theoretical NF/RO membrane properties needed to optimize product water quality and specific energy consumption, (3) and evaluate

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model results with bench-scale studies of seawater desalination using commercially available NF/RO membranes. We have created a simple analytical model that estimates full-scale NF/RO system product water quality and specific energy consumption considering a membrane’s water permeability and TDS rejection, feed water concentration, total system flux, and concentration polarization. In addition, we have developed a bench scale NF/RO seawater desalination simulator for testing real NF/RO membrane performances in the modeled scenarios.

Model results for single-pass SWRO systems suggest the theoretical minimum specific energy consumption is not yet realized, the effects of concentration polarization are non-negligible, and increasing SWRO membrane permeability beyond that of modern BWRO membranes may yield little benefit. These results may have important implications and could be used to guide future efforts to engineer better performing SWRO membranes and modules. These results and their implications will be discussed in the presentation. Model simulations are also performed to elucidate the optimal combination of first and second pass NF/RO membrane rejections for a two-pass system. Simulations consider three scenarios in which (a) membrane resistance and CP are neglected, (b) membrane resistance is neglected, CP is considered, and (c) membrane resistance and CP are considered. These results highlight the important role of membrane resistance and CP in multi-pass system performance. Finally, three scenarios have been tested in the laboratory: (a) two-pass NF membrane followed by a high-rejection BWRO membrane, (b) two-pass seawater NF (SWNF) membrane followed by another SWNF membrane, and (c) a one-pass SWRO membrane. All three scenarios give desalination performance that may have practical value. In this presentation we will present details of our modeling and experimental results, and discuss the implications for single-pass and multi-pass NF/RO seawater systems.

Reference:

1.Sauvet-Goichon, B., Ashkelon desalination plant -- A successful challenge. Desalination, 2007. 203(1-3): p. 75.

2.Lomax, I., Experiences of Dow in the field of seawater reverse osmosis. Desalination, 2008. 224(1-3): p. 111.

3.Harrison, C.J., et al., Bench-scale testing of nanofiltration for seawater desalination. Journal of Environmental Engineering-Asce, 2007. 133(11): p. 1004-1014.

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Desalination I – 6

Monday July 14, 5:00 PM-5:30 PM, O’ahu

Performance Testing of a Large Seawater RO Desalination Plant

A. Khawaji (Speaker), Royal Commission for Jubail & Yanbu, Yanbu Al-Sinaiyah, Saudi Arabia J. Wie, Saudi Arabian Parsons Limited, Yanbu Al-Sinaiyah, Saudi Arabia, [email protected]

Yanbu Industrial City in Saudi Arabia depends upon seawater desalination for its entire fresh water supply. The fresh water is supplied by a desalination complex that consists of a multi- stage flash distillation plant with a capacity of 95,760 m3/day and a reverse osmosis (RO) plant with a capacity of 50,400 m3/day. The RO plant was constructed recently by the Royal Commission for Jubail & Yanbu. This seawater RO plant is made up of six 8,400 m3/day permeate trains. The plant consists of five basic components: seawater supply, feedwater pretreatment, high pressure pumping, RO membranes, and permeate post-treatment. The RO plant is designed to desalt the seawater with total dissolved solids (TDS) of 46,400 ppm at 22 °C seawater temperature. RO feedwater is treated with various chemicals such as sulfuric acid, ferric chloride, sodium bisulfite, and sodium hypochlorite. Filtration is carried out in two stages with dual media filters and cartridge filters. The multistage high pressure centrifugal pumps are operated at 64 to 76 kg/cm2g. The high pressure pumps are coupled to energy recovery turbines for energy recovery from the concentrated brine stream to reduce electrical pumping costs. The RO membranes are made of cellulose triacetate using the hollow fine fiber configuration. The plant is installed with 1,824 RO membrane elements. Salt rejection by the membranes is approximately 99.4%. The plant produces permeate with a maximum TDS of 500 ppm at a minimum recovery ratio of 35% for the single pass permeators. The plant is equipped with a distributed control system using state-of-the-art computerized technology. This paper presents the major plant design features and the results of the testing conducted to determine whether the plant performance guarantee described in the contract technical specifications can be met. The performance testing includes normalized permeate flow rates, permeate water quality, recovery rates, chemicals consumption, power consumption, silt density index values and residual chlorine concentrations of seawater and filtered water, permeate pHs, and bacteriological tests of product water.

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Composite Polymeric Membrane Formation – 1 – Keynote

Monday July 14, 2:15 PM-3:00 PM, Waialua

A New Method to Fabricate Membranes using Glassy Self Assembly Templating

G. Feng, University of Cincinnati, Cincinnati, OH, USA C. Ho (Speaker), University of Cincinnati, Cincinnati, OH, USA C. Co, University of Cincinnati, Cincinnati, OH, USA, [email protected]

Ultrafiltration and microfiltration membranes play an integral part in downstream processing operations in biotechnology and pharmaceutical industries. Ultrafiltration membranes are traditionally manufactured by air casting, immersion, or melt casting of polymer solutions. In almost all cases however, the pores as defined by the percolated nodules of polymer, are very polydisperse and geometrically ill-defined. As a result, most ultrafiltration membranes have relatively broad molecular-weight cut-offs and sub-optimal hydraulic permeability. A promising approach for manufacturing ultrafiltration membranes with uniform pores relies on the polymerization of self-assembled surfactant nanostructures. Many research groups have investigated polymerizing bicontinuous surfactant structures. However, instead of forming ultrafiltration membranes with nanometer size pores, membranes with micron-size pores much larger than that of the surfactant template are consistently reported following polymerization. This is due to breakthrough of the surfactant templates, which typically rearrange on a time scale faster than the polymerization. To overcome this challenge in an economical and practical way, the approach proposed here replaces water in traditional self-assembled surfactant templates with glassy sugars. Successful polymerization of these templates would potentially lead to membranes with highly uniform and finely tunable nanometer-size pores whose dimensions are dictated by the quasi-equilibrium thermodynamics of the glassy sugar/surfactant template. After polymerization, the sugar and surfactant can be readily rinsed off with water and recycled, thereby foregoing the use of toxic solvents prevalent in traditional membrane manufacturing processes.

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Composite Polymeric Membrane Formation – 2

Monday July 14, 3:00 PM-3:30 PM, Waialua

Ultra-Thin Polymeric Interpenetration Network with Enhanced Separation Performance Approaching Ceramic Membranes for Biofuel

L. Jiang (Speaker), National University of Singapore, Singapore Y. Jean, University of Missouri- Kansas City, Kansas City, MO, USA, [email protected] H. Chen, University of Missouri- Kansas City, Kansas City, MO, USA T. Chung, National University of Singapore, Singapore

In this study, we report the discovery of novel molecular engineering and membrane fabrication that can synergistically produce polymeric membranes exhibiting separation performance approaching ceramic membranes in biofuel dehydration. Biofuel has emerged as one of the most strategically important sustainable fuel sources. The success of biofuel development is not only dependent on the advances in genetic transformation of biomass into biofuel, but also on the breakthroughs in separation of biofuel from biomass. The ‘separation’ alone currently accounts for 60 to 80% of the biofuel production cost. There mainly exist two kinds of materials applied for biofuel separation by pervaporation, namely, ceramic membranes and polymer membranes. Ceramic membranes made of sophisticated processes have shown separation performance far superior to polymeric membranes. Nevertheless, ceramic membranes seriously suffers fragility and high fabrication cost, and polymeric membrane with excellent flexibility is still attractive. For the polymeric membrane, extensive studies exist on how to fine tune the membrane’s pore structure including it’s cross-section morphology by the selection of polymer solvents and non-solvents, additives, residence times and other parameters during non-solvent induced phase separation. The key for the performance is the very thin ‘skin’ layer which enables a high permeability. The newly discovered membranes in current work are fabricated by dual-layer co-extrusion technology in just one step through phase inversion. The best performance obtained was a total flux of ~3.9 kg/m2-hr with a separation factor of ~800 in tert-butanol dehydration. The combined molecular engineering and membrane fabrication approach may revolutionize future membrane research and development for purification and separation in energy, environment, and pharmaceuticals.

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Composite Polymeric Membrane Formation – 3

Monday July 14, 3:30 PM-4:00 PM, Waialua

PTFE-Polyamide Thin-Film Composite Membranes from Interfacial Polymerization for Pervaporation Dehydration of Alcohol-Water Mixtures

C. Yu, Chung Yuan University, Chung-Li, Taoyuan, Taiwan R. Jeng (Speaker), National Chung Hsing University, Taichung, Taiwan Y. Liu, Chung Yuan University, Chung-Li, Taoyuan, Taiwan, [email protected] J. Lai, Chung Yuan University, Chung-Li, Taoyuan, Taiwan

Thin-film composite (TFC) membranes are attractive in membrane separations. The thin selective layers of TFC membranes warrant their high fluxes and high selectivitity in separation. Consideration of the superior chemical resistance, good thermal stability, and high mechanical strength of poly (tetrafluoroethylene) (PTFE), in this work we report attempts on preparation of PTFE-polyamide (PA) TFC membranes by interfacial polymerization. The pervaporation dehydration performance of the prepared membranes on alcohol- water mixtures is also examined. The compatibility between the PTFE substrates and the monomer solutions in interfacial polymerization is the key issue in the preparation of PTFE-PA TFC membranes. We demonstrated several modification approaches on PTFE surfaces and the modified PTFE films are applied to preparation of TFC membranes. It has been found that incorporation of an amine- terminated layer on the PTFE surface provides good compatibility and adhesion to PTFE/PA interfaces by increases in hydrophilicity and formation of covalent linkages between PTFE and PA. The amine-terminated layer is introduced to PTFE surfaces via both of surface-initiated polymerization and surface plasma deposition polymerization. Chemical structure characterizations are performed. The morphology of the TFC membranes are also observed with electron microscopy. The composite membranes are applied to pervaporation dehydration processes on a 70 wt% isopropanol aqueous solution. The membranes are stable under the pervaporation dehydration operations and show a high permeation flux of 1720 g/h.m2 and a separation factor of 177. These PTFE-based thin-film composite membranes are potentially useful in pervaporation separation for other organic mixtures.

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Composite Polymeric Membrane Formation – 4

Monday July 14, 4:00 PM-4:30 PM, Waialua

Preparation of Poly(vinyl alcohol) Composite Reverse Osmosis and Nanofiltration Membranes

G. Ramos (Speaker), Federal University of Rio de Janeiro, PEQ, Chemical Engineering, Brazil, [email protected] B. Cristiano, Federal University of Rio de Janeiro, PEQ, Chemical Engineering, Brazil

Nowadays, in reverse osmosis (RO) and nanofiltration (NF) processes, the thin-layer composite polyamide (PA) membrane is accepted as a reference system. These PA membranes are widely commercialized for these processes due to their excellent saline rejection and hydraulic permeability. However, one of the major factors reducing the overall performance of the RO and NF processes is fouling. Membrane fouling can cause irreversible loss of system productivity. Among the types of fouling, biofouling is the one of the most serious fouling problems and polyamide membranes are particularly susceptible to it.

In addiction, the major concern with PA membranes is their lost of performance when exposed to oxidizing agents, such as aqueous chlorine, commonly used in water disinfection. It is known that after an exposition to chorine of 500 to 2,000 ppm.h membranes salt rejection decreases and the water flux increase. In order to protect the membrane, the chlorine should be completely removed in the pre-treatment stage, increasing costs and allowing the growth of microorganisms throughout the system and, especially, the formation of biofilm on the surface of the membrane. Also, sodium bi-sulfite, added to remove chlorine, attacks the PA membrane under presence of heavy metals, such as Cu, Co, etc.

New polymer material with enhanced resistance to fouling and oxidation is subject of many research works. By far, the simplest technique to prepare a composite membrane is the dip-coating using a diluted polymer solution, which allows the use of several polymers to prepare the top layer. Poly(vinyl alcohol) (PVA) is an attractive material because it is an hydrophilic polymer with low fouling potential, has chemical stability, low cost and it can be easily deposit on top of many existing porous supports. Furthermore, the hollow fibers have advantages in relation to the flat membranes: they are self supported and appropriated for compact modules with large area of membrane.

The aim of this work is to investigate the synthesis of reverse osmosis and nanofiltration composite membranes by using PVA as top layer, prepared by dip coating technique. The molecular packing density of PVA dense layer was varied by choosing the parameters that affect the crosslinking reaction of PVA molecules. The PVA 80 and 99% hydrolyzed was crosslinked by using different

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crosslinking agents, citric acid, oxalic acid and maleic acid, and different temperatures: 60, 80, 100 and 150°C. The characterization of the crosslinked PVA was performed by DSC, TGA and FTIR analysis, as well as water swelling degree.

Ultrafiltration poly(ether sulfone) hollow fibers with cut-off of 50 kDa were used as porous support for a selective layer of PVA. The composite fibers were characterized by SEM and by permeation of sodium sulfate solution in a lab set-up. The transport properties in combination with morphological analysis allow establishing criteria for selection of the best conditions to prepare PVA composite membranes for RO and NF processes.

The results with these composite membranes showed salts rejection were around 95%. To evaluate the chlorine resistance, PVA films were analyzed by FTIR after immersion in chlorine solution. Results indicate that it is a promising method to produce chlorine resistant membranes.

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Composite Polymeric Membrane Formation – 5

Monday July 14, 4:30 PM-5:00 PM, Waialua

Experimental Verification of Effect of Support on Membrane Performance

R. Takagi (Speaker), Shukugawa Gakuin College, Nishinomiya, Japan, [email protected] A. Pihlajamäki, Lappeenranta University of Technology, Lappeenranta, Finland T. Shintani, Nitto Denko Corporation, Osaka, Japan M. Nyström, Lappeenranta University of Technology, Lappeenranta, Finland

Generally, a membrane is a composite, made by forming a skin layer on a support. The ion permeability coefficient of the support is generally different from that of the skin layer. Thus, the characteristic properties of the support also affect membrane performance. The effect of the support on the membrane performance has been theoretically studied. It is already reported that the variation of membrane charge, pore radius, porosity and thickness of the support affect the ion flux and, then, affect the rejection of the membrane. It is very important to know the effect of the support on the membrane performance to design a new membrane. Unfortunately, it is very difficult to verify the effect of the support experimentally. It will be possible to verify the effect of the support experimentally, if the characteristic properties of the skin layer and the support are known separately. It is possible to characterize the support as a separate membrane experimentally. However, it is very difficult to experimentally characterize the skin layer as a separate membrane, since the skin layer is very thin and it is almost impossible to obtain the skin layer as a separate membrane.

In this paper, a potential way to experimentally verify the effect of the support is discussed. The composite membrane will be asymmetric with respect to membrane charge, since the porosity and the pore radius of the support are different from those of the skin layer. It is theoretically reported that the membrane potential of the asymmetric membrane with respect to membrane charge varies by changing the membrane setting from (bulk solution 1|skin layer | support | bulk solution 2) to (bulk solution 1| support | skin layer | bulk solution 2). The membrane potential is an electric potential difference generated between the bulk solutions when the membrane separates two bulk solutions with different concentration of electrolyte or different kind of electrolyte. Then, if the skin layer and the support are homogeneously charged and the membrane potential of the composite membrane varies by changing the membrane setting, it shows that the membrane is asymmetric with respect to membrane charge. It means that the effect of the support is not negligibly small and that the support affects the membrane performance.

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Commercial polymeric membranes are used as the composite membranes. The skin layer of commercial polymeric membranes is about 0.1~0.2μm in thickness. It is reasonable to assume that the skin layer is homogeneously charged, since it is very thin. The charge density of the skin layer will be higher than that of the support, since the pore radius of the skin layer is smaller than that of the support. On the other hand, the support of commercial polymeric membranes is about 150μm in thickness (PSF 50μm and nonwoven 100 μm) and has a non-homogeneous structure. If the membrane potential of the support as a separate membrane does not vary by changing the membrane setting, it means experimentally that the support is homogeneous with respect to membrane charge. Thus, it will be an experimental evidence that the support affects the membrane performance, if the membrane potential of the support as a separate membrane does not vary by changing the membrane setting and the membrane potential of the commercial membrane varies by changing the membrane setting.

The membrane potential was measured using NaCl as the electrolyte, keeping the bulk concentration ratio as two. The membrane potential of the support as a separate membrane did not vary by changing the membrane setting. It means that the support is homogeneous with respect to membrane charge, regardless of its geometric structure. On the other hand, the membrane potential of the commercial membranes (Nitto Denko Corporation CPA3 and ES10-D4) varied by changing the membrane setting. This fact verifies experimentally that the support affects the membrane performance of composite membranes such as the commercial membranes studied here.

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Composite Polymeric Membrane Formation – 6

Monday July 14, 5:00 PM-5:30 PM, Waialua

Study on Improvement of Composite Reverse Osmosis Membranes

C. Gao (Speaker), The Development Center of Water Treatment Technology, Hanzhou, China, [email protected] Y. Zhou, The Development Center of Water Treatment Technology, Hanzhou, China Q. An, College of Materials Science and Chemistry, Zhejiang University, Hangzhou, China S. Yu, The Development Center of Water Treatment Technology, Hanzhou, China L. Wu, The Development Center of Water Treatment Technology, Hanzhou, China

The current worldwide expansion of the RO application has resulted from the introduction of thin-film-composite (TFC) membranes by interfacial polycondensation. The TFC membranes are composed of thin skin layers and supporting substrates. Some studies have been carried out recent years on the improvements of both the skin layers and supporting substrates. For the improvements of supporting substrates, the relationship between cloud point, zero viscosity and rheological properties of casting solution and structure and performance of membrane was analyzed. The formation mechanism of phase inversion membrane was investigated. The supporting PSF membranes with cross-section structures of sponge-like with density gradient were obtained. For the improvements of thin skin layers, a few of functional monomers such as SMPD, HDA, ICIC and CFIC, for interfacial polymerization were synthesized. The effect of compositions of water phase (diamine) and oil phase (carbonyl chloride) on membrane performance were investigated. The procedure and parameter control of membrane preparation were optimized. The post treatment of obtained TFC membrane was conducted for further improvement. The relation between among performance and chemical structure, morphology of membranes was investigated. The composite membranes with high flux, high rejection and anti-fouling property were produced comparing with original membranes.

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Oral Presentation Abstracts

Morning Session

Tuesday, July 15, 2008

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NAMS Alan S. Michaels Award – 1a

Tuesday July 15, 8:15 AM-8:50 AM, Kaua’i

Some Reflections and Projections Based on Thirty Five Years in Membranes

W. Koros (Speaker), Georgia Institute of Technology, Atlanta, GA, USA, [email protected]

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NAMS Alan S. Michaels Award – 1b

Tuesday July 15, 8:50 AM-9:15 AM, Kaua’i

A Versatile Membrane System for Bulk Storage and Shipping of Produce in a Modified Atmosphere

S. Kirkland, University of Texas at Austin, Austin, TX, USA R. Clarke, Landec Corporation, Menlo Park, CA, USA D. Paul (Speaker), University of Texas at Austin, Austin, TX, USA, [email protected]

After harvesting, fruits and vegetables continue to respire, i.e., consuming oxygen and giving off carbon dioxide. Such produce will retain freshness and market value much longer if the respiration process is slowed down, e.g., by refrigeration. Produce shelf life can be extended further by storage in an appropriate gaseous atmosphere, e.g., oxygen and carbon dioxide composition, within an optimal range specific to each type of produce. Modified atmosphere packing, MAP, employs membranes to achieve the specific atmosphere needed; commercial application of this concept is growing rapidly for small, disposable retail packages. Membrane technology can also be used to create appropriate atmospheres in reusable large-scale bulk containers for storage and shipping of produce. However, this approach would be even more widely used if a versatile system could be designed to accommodate the requirements of different types of produce without altering the hardware, i.e., one membrane system could be used to create different compositions of oxygen and carbon dioxide, depending on what produce is being shipped or stored at a given time. A scheme is proposed here that uses a selective membrane and a non-selective membrane acting in parallel. The relative amount of gas exchange through the non-selective membrane can be adjusted by varying the volumetric air feed rate to its upstream surface; this will, in turn, adjust the steady state composition of the gas around the produce. A quantitative model for this scheme and sample calculations are presented to illustrate the concept and how to design such a system where the atmosphere created can be set to the desired range by adjusting the air feed rate.

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NAMS Alan S. Michaels Award – 2

Tuesday July 15, 9:30 AM-9:55 AM, Kaua’i

Enhancing Natural Gas Purification with Advanced Polymer/Molecular Sieve Composites

S. Miller (Speaker), Chevron Energy Technology Company, Richmond, CA, USA D. Vu, Chevron Energy Technology Company, Richmond, CA, USA, [email protected]

Membranes have been of continuing interest to the petroleum and chemical industries for gas separations. While glassy, polymeric membranes have provided efficient performance to date, significant improvements over current membrane technology will likely require novel materials. This paper will review the development and status of a new technology based on composite membranes, termed mixed matrix membranes, of polymer matrices in which molecular sieves are dispersed to give enhanced separation of natural gas from its impurities compared to membranes of the polymer alone.

The technology is particularly of interest to the separation of natural gas from its impurities, such as CO2 and H2S.

In laboratory testing, the composite membranes, composed of molecular sieves in commercial membrane polymer matrices, showed significant improvement in both selectivity and flux compared to membranes of the polymers alone for the separation of CO2 from natural gas. Enhancements were obtained using both carbon molecular sieves and small pore zeolites.

While membranes have been of interest due to their compactness, light weight, and ease of operation, there has not been widespread application due to low selectivity and flux, and limited robustness. This has led researchers to study molecular sieve membranes, including carbon molecular sieve and zeolitic materials. While these membranes offer very attractive properties, their cost, difficulty of commercial scale manufacture, and brittleness remain major challenges. Mixed membrane technology, which combines benefits of molecular sieves with the ease and low cost of processing polymer membranes, offers a potential solution to these challenges.

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NAMS Alan S. Michaels Award – 3

Tuesday July 15, 9:55 AM-10:20 AM, Kaua’i

High Performance Ultrafiltration: What Can We Learn from the Gas Separations Experts?

A. Zydney (Speaker), The Pennsylvania State University, University Park, PA, USA, [email protected]

Historically, there has been relatively little interaction between researchers and practitioners working on ultrafiltration and gas separation membranes. Not only are these application areas very different, the fields use very different terminology and theoretical frameworks to describe the performance of the membrane processes. For example, ultrafiltration membranes are typically characterized in terms of the nominal molecular weight cut-off, a poorly-defined term that provides relatively limited information on membrane performance. In contrast, gas separation membranes are typically characterized using a Robeson plot, which provides a quantitative framework for comparing the performance of different membrane materials. This presentation will examine a new approach for understanding the behavior of ultrafiltration membranes that draws directly from the gas separations literature, including much of the work done by Bill Koros' group over the past 20 years.

Solute transmission through semipermeable ultrafiltration membranes is proportional to the solute partition coefficient between the bulk solution and the membrane pores and to the rate of hindered solute convection along the pore length, which is in many ways analogous to the solution - diffusion analysis used to describe transport through gas separation membranes. This suggests that it should be possible to describe the performance of ultrafiltration membranes using a "selectivity - permeability" trade-off plot, analogous to the classical Robeson plot used for gas separation membranes. Experimental data for traditional ultrafiltration processes and for high performance ultrafiltration for protein separations have been successfully analyzed in terms of this selectivity - permeability tradeoff, providing a quantitative framework for comparing the performance of different ultrafiltration membranes. The results clearly show the presence of an "upper bound" for the performance of commercial ultrafiltration membranes, analogous to the upper bound seen with gas separation membranes. The theoretical underpinnings for this upper bound are discussed using appropriate models for the protein partition coefficient and the hindrance factor for convection. High performance ultrafiltration membranes have been developed by altering the solute partition coefficient into the membrane pores, analogous to the development of solubility- selective gas separation membranes. These results highlight some of the underlying similarities between ultrafiltration and gas separation membranes, and they demonstrate that there are real

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opportunities for improving membrane performance by drawing from leading developments in both fields.

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NAMS Alan S. Michaels Award – 4a

Tuesday July 15, 10:20 AM-10:45 AM, Kaua’i

Membranes and Reactors and Integration, Oh My!

M. Rezac (Speaker), Kansas State University, Manhattan, KS, USA, [email protected]

Catalytic reactors are employed to convert a substrate to a product. Frequently, the conversion is incomplete and not perfectly selective. This requires the use of more or less complicated down-stream separation processes to recover the desired pure product. Membrane reactors offer the opportunity to control the reaction environment resulting in a more desirable product mixture. In this presentation, we’ll examine several forms of membrane reactors with an evaluation of the status of each and any remaining barriers to commercialization.

The overall results achieved with these systems include: (1) conversions well-beyond the conventional equilibrium limitation, (2) reaction rates and product selectivities significantly altered by control of the reaction media, and (3) selective addition of hydrogen via a membrane reactor can positively influence reaction product composition.

The impact of processing conditions and membrane properties on the reaction product spectrum will be discussed in this presentation.

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NAMS Alan S. Michaels Award – 4b

Tuesday July 15, 10:45 AM-11:10 AM, Kaua’i

Membranes for Energy Efficiency and Sustainability

K. Murphy (Speaker), Air Products, St. Louis, MO, USA, [email protected]

Among of the most significant attributes of a great teacher is the ability to inspire others. This presentation was inspired by the efforts of Professor William J. Koros, the 2008 Alan Michaels Award honoree. Bill has spoken widely to foster recognition of the contributions that membrane science and technology make to the enhanced energy efficiency of large-scale industrial processes. Bill has encouraged others to contribute meaningfully to a more sustainable future worldwide.

Membranes applied to many separation and purification applications have contributed, and can in the future contribute, significantly to more efficient processes in a wide variety of industries. Bill’s efforts have encouraged the membrane community and others to recognize that very large-scale societal problems can be meaningfully addressed by what we collectively do. Membrane processes positively impact society in many ways, from purifying drinking water, to improving efficiency in production of agricultural fertilizers for food crop production, to enhancing food stuffs’ distribution, to improving efficiencies of a variety of processes for the production and utilization of energy resources. Looking to the future, significant opportunities and challenges remain, where improved membrane technologies could make substantial further contributions to energy efficiency and sustainability.

This presentation is an overview, designed to provide perspective within a worldwide context. It will use a diverse range of application examples to demonstrate utility and potential of membrane technology to serve society’s growing needs. The intent of the presentation is to reflect on the past in hopes of inspiring current and next generations of engineers and scientists to help achieve that better future.

Among his many contributions, through his substantial technical work and his training of many top-notch graduates, Bill has done much to further the attainment of a better future. Many people would be proud to leave such a legacy. Bill’s message includes an implicit urging that we look beyond the parochial to the larger view, of how we impact the larger world by our actions. This presenter sincerely hopes to honor the 2008 Alan Michaels Award winner,

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Bill Koros, by furthering his vision that all of us in the membrane community can contribute meaningfully to a better future.

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NAMS Alan S. Michaels Award – 5

Tuesday July 15, 11:10 AM-11:35 AM, Kaua’i

On the Time Scales of Sorption Induced Plasticization

M. Wessling (Speaker), University of Twente, The Netherlands, [email protected]

This contribution focuses on the phenomenon of sorption induced plasticization. The term plasticization is frequently used to describe a variety of experimental observations ranging from for instance (a) time-independent but concentration dependent diffusion coefficients to (b)very slow (relaxational) changes in volume dilation and dynamic weight uptake.

The presentation focuses on the plasticization phenomena in three different polymers: 1. A glassy polyimide (Matrimid) 2. A glassy ionomer (sulphonated PEEK) 3. A segmented block-copolymer PEBAX

Dynamic sorption studies are carried out for a variety of different gases and vapors such as noble gases, hydrocarbons and water.

These data are used to reflect on the time-scales of polymer dynamics as compared to the time-scales of penetrant motion in order to explain plasticization in rubbery as well as glassy polymers.

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NAMS Alan S. Michaels Award - 6

Tuesday July 15, 11:35 AM-12:00 AM, Kaua’i

Recent Developments in Membranes for Gas Separation Applications

I. Pinnau (Speaker), Membrane Technology and Research., Inc., Menlo Park, CA, USA, [email protected]

Gas separation-based membrane processes were introduced about thirty years ago. The first membrane types were i) integrally-skinned asymmetric cellulose acetate membranes, ii) silicone thin-film composite membranes, and multilayer polysulfone/silicone composite membranes. These membrane types were successfully applied in petrochemical and natural gas applications as well as production of nitrogen from air and recovery of organic vapors from a variety of waste gas streams. Ideal membranes for gas separation applications must fulfill the following requirements: a) high gas permeance to minimize membrane area requirements, b) high selectivity to provide high product purity and c) good tolerance to contaminants in the feed gas. In the past decade many polymers with improved permeability and selectivity were developed; however, very few were scaled up as high-performance membranes for commercial applications. This presentation will highlight some of Bill Koros' achievements in the field of gas separation membranes, including: materials science aspects, development of ultrathin-skinned asymmetric membranes, and mixed-matrix polymer/inorganic hybrid membranes.

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NAMS Alan S. Michaels Award - 7

Tuesday July 15, 12:00 AM-12:25 AM, Kaua’i

Various Poly(dimethylsiloxane) Membranes for Removal of Volatile Organic Compounds from Water

T. Uragami (Speaker), Kansai University, Suita, Osaka, Japan, [email protected] T. Ohshima, Kansai University, Suita, Osaka, Japan T. Miyata, Kansai University, Suita, Osaka, Japan

In this study, five kinds of polymer membranes such as poly(methyl methacrylate) (PMMA) and poly (dimethylsiloxane) (PDMS) graft copolymer membranes (Membrane A), PFA-g-PDMS/PMMA-g-PDMS membranes surface-modified with a fluorine- containing graft copolymer (PFA) (Membrane B), CA/PMMA-g-PDMS membranes added calixarene (CA) to PMMA-g-PDMS (Membrane C), PDMS dimethylmethacrylate (PDMSDMMA) membranes cross- linked with various cross-linkers (Membrane D), and CA/cross-linked PDMSDMMMA membranes added CA into cross-linked PDMADMMM (Membrane E) were prepared for the removal of volatile organic compounds (VOCs) from water. Permeation and separation characteristics for an aqueous solution of dilute VOC through the above membranes during pervaporation (PV) are discussed from the viewpoints of chemical and physical characteristics of those membranes.

Membrane A increased benzene/water selectivity and permeation rate with increasing DMS content. The benzene/water selectivity and permeation rate of membrane A increased dramatically at a DMS content of more than about 40 mol%. It was recognized by transmission electron microscopy (TEM) that Membrane A had a microphase-separated structure, and a continuous PDMS phase in the microphase-separated structure of Membrane A played an important role for the benzene/water selectivity of an aqueous solution of dilute benzene through this membrane.

In Membrane B, it was confirmed by the contact angle and X-ray photoelectron spectroscopy measurements that PFA was localized on the air- side surface of membrane. It became apparent from TEM that adding a PFA of less than 1.2 wt% did not affect the morphology of the microphase- separated Membrane A, but adding PFA over 1.2 wt% resulted in a morphology change from a continuous PDMS phase to a discontinuous PDMS phase. The addition of a small amount of PFA into the microphase-separated Membrane A enhanced both the permeability and selectivity for a dilute aqueous solution of benzene.

On the other hand, in Membrane C both the permeability and the benzene/water selectivity were enhanced by increasing the CA content, due to the affinity of the

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CA for benzene. TEM observations and differential scanning calorimetry measurements revealed that Membrabe C had a microphase-separated structure consisting of a PMMA phase and a PDMS phase containing CA.

On the basis of the above results, Membranes D, which has a continuous PDMS phase in the whole of membrane, were prepared. In Membrane D, both the permeability and benzene/water selectivity of the membranes were enhanced with increasing divinyl compound content as the cross-linker, and were significantly influenced by the kind of divinyl compound. PDMSDMMA membranes cross- linked with divinyl perfluoro-n-hexane (DVF) showed very high membrane performance during PV.

Membrane E also increased both the permeation rate and the benzene/water selectivity with increasing CA content.

The membrane performance for the removal of VOCs of these membranes was in the order of Membrane E > Membrane D > Membrane C > Membrane B > Membrane A. The membrane performance of modified PDMS membrane added CA of 0.4 wt% to PDMSDMMA membrane cross-linked with DVF of 90 mol% in the membrane (Membrane D) was very excellent; the normalized permeation rate and the separation factor for an aqueous solution of 0.05 wt% benzene were 1.86 [10-5 kgm/(m2h)] and 5027, respectively.

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Nanofiltration and Reverse Osmosis II - Imaging and Characterization – 1 – Keynote

Tuesday July 15, 8:15 AM-9:00 AM, Maui

On the Correlation Between MWCO Values for Nanofiltration Membranes and Quantitative Porosity Analysis Using Variable Energy Positron Beams.

J. De Baerdemaeker (Speaker), Ghent University, Gent, Leuven, Belgium, [email protected] K. Boussu, KU Leuven, Leuven, Belgium B. Van der Bruggen, KU Leuven, Leuven, Belgium M. Weber, Washington State University, Pullman WA, USA K. Lynn, Washington State University, Pullman WA, USA

Correlations between the MWCO (Molecular Weight Cut Off) and the pore size in the skin layer of nanofiltration membranes is still under debate due to the lack of independent techniques to determine in a quantitative way the porosity of the skin layer. It might even be stated that progress in nanofiltration (NF) is tempered by the lack of knowledge of fundamental properties such as porosity.

Using positron and positronium spectroscopy, valuable information can be gained regarding the true influence of porosity on the transport of molecules through nanofiltration membranes (NFM). The use of variable energy positron beams enables depth profiling of the porosity in NFM. By measuring the lifetime of the positronium in the skin layer of the membrane the size and distribution of the pores can be determined. This techniques has only very recently been introduced into the nanofiltration field[1,2,3].

As will be demonstrated complementary information is gained by comparing the depth profile porosity evolution with high resolution cross section images using a dualbeam FIB/SEM (Focused Ion Beam - Scanning Electron Microscope).

The results presented within the scope of this research focuse on the correlation of MWCO values measured for different commercial nanofiltration membranes with positron results. This comparison not only indicates that the absolute size of the pores does not seem to be the crucial parameter for the understanding of NF but presents strong evidence on how the pore distribution determines the selectivity in these membranes.

This implies that the current models which describe NF should be reexamined. These findings are crucial for the modeling of NF and might open the path to the final goal of NF, the production of tailor made NFM. This new study should also stimulate the membrane community to consider and use positronium

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spectroscopy as a novel research tool for the fundamental understanding of porosity in membranes used in different technologies.

[1]K. Boussu at al. ChemPhysChem 2007, 8, 370. [2]H. Chen et al. Macromolecules 2007, 40, 7542. [3]D. Cagill at al. MRS Bulletin January 2008.

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Nanofiltration and Reverse Osmosis II - Imaging and Characterization - 2

Tuesday July 15, 9:30 AM-10:00 AM, Maui

Positron Annihilation Spectroscopy (PAS): A New Powerful Technique to Study Membrane Structure

A. Cano-Odena (Speaker), Center for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Leuven, Belgium P. Vandezande, Center for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Leuven, Belgium K. Hendrix, Center for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Leuven, Belgium R. Zaman, Center for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Leuven, Belgium K. Mostafa, NUMAT (Nuclear Methods in Materials Science), Dept Subatomic and Radiation, Gent, Belgium J. De Baerdemaeker, NUMAT (Nuclear Methods in Materials Science), Dept Subatomic and Radiation, Gent, Belgium I. Vankelecom, Center for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Leuven, Belgium, [email protected]

Introduction Positron annihilation spectroscopy (PAS) is a nondestructive technique used to study defects and open volumes in materials based on the analysis of the ³-ray radiation emitted due the annihilation of positrons (antimatter counterpart of the electron) with electrons of the material. Positrons injected in a polymer sample can either annihilate freely or capture an electron forming a meta-stable bound state positronium(Ps) with two possible states depending on the relative orientations of the spins of the electron and the positron:ortho- positronium(o-Ps) and para-positronium(p-Ps). The use of a variable low energy positron beam enables the study of the characteristic annihilation of the positronium from the surface down to a couple of micron. Hence with a positron beam a depth profile of the porosity is measured. O-Ps has a longer lifetime in vacuum and gets preferentially localized in the free volume of the polymer. In positron annihilation lifetime spectroscopy (PALS) the decrease in o- Ps lifetime is related to free volume cavities radius. Despite clear benefits over more indirect characterization techniques PAS has only recently been applied in membrane research [1,2]. Its use will be here extended to an in- depth characterization of the morphology of the polymeric structure allowing to correlate physical defects at atomic scale (free volume) with membrane performance (permeability, selectivity).

Thanks to increased environmental concerns and the search for cleaner and energy-efficient technologies, solvent resistant nanofiltration (SRNF)[3] has received enhanced attention as a promising technique, offering a sustainable alternative for conventional energy-intensive and waste-generating separations. SRNF holds a vast potential in food, (fine-)chemical, pharmaceutical and

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petrochemical industries. In view of the expected growth of the SRNF market and the relatively limited number of commercial membranes, a clear need still exists to develop robust membranes to solve separation problems in existing industrial processes and open new application areas. Polar aprotic solvents (NMP, DMF, DMSO) are frequently applied in pharmaceutical and chemical processes. Chemical cross-linking with diamines allows preparing chemically stable asymmetric polyimide (PI)- based SRNF membranes that have been successfully applied in polar aprotic solvents and THF[4].

Objectives -Characterize skin layer thicknesses, densities, differences in porosity and porosity evolution between skin layers and sublayers of of polyimide (PI)-based membranes prepared by phase inversion with PA(L)S. -Correlate the information obtained through PA(L) S with performance data in laboratory-made and commercial PI membranes (Starmem") and other characterization techniques to study the influence of synthesis parameters (polymer concentration, evaporation time) and post- treatment conditions (chemical cross-linking) on the performance of asymmetric PI (P84) based membranes in filtrations of Rose Bengal (RB, 1017 Da) in 2-propanol (IPA), DMF and THF.

Results and discussion As expected, an increase of the initial polymer concentration in the casting solution, containing P84 in a NMP/THF mixture improves RB retention but decreases the permeability. It can be related, to the formation of a denser skin layer, also observed from PAS profiles and confirmed by SEM. Increasing the evaporation time prior immersion in the coagulation bath drops IPA and THF permeabilities but no significant changes in the RB retention were observed. The longest evaporation times have no effect in performance and no differences were observed in PAS profiles. For membranes chemically cross-linked, a 90% flux drop was noticed as compared to uncross-linked ones together with better retentions. Solvent fluxes followed the order THFDMFHIPA. The chemical cross-linking involves the transformation of imide bonds to amide bonds, reducing the interstitial space among chains and thus the free volume, which results in a decrease in the top layer thickness, as confirmed by PAS.

Conclusions laboratory-prepared P84-based SRNF membranes showed higher fluxes compared to the commercial ones. From the analysis of profiles of the energy of annihilation, differences in porosities between top and support layers in membranes and different evolution from the skin layer to the mesoporous regions can be estimated and be related to the performance results from filtration experiments.

References

[1] K. Boussu at al. ChemPhysChem 2007, 8, 370.

[2] H. Chen et al. Macromolecules 2007, 40, 7542.

[3] P. Vandezande et al. Chem. Soc. Rev. 2008, 37, 365.

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[4] K. Vanherck et al. Accepted for publication in J. Membr. Sci.

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Nanofiltration and Reverse Osmosis II - Imaging and Characterization – 3

Tuesday July 15, 10:00 AM-10:30 AM, Maui

Characterization of Biofouling Development of Spiral Wound Membrane Systems: The First NMR Study

D. Graf von der Schulenburg, University of Cambridge, Cambridge, UK J. Vrouwenvelder (Speaker), Wetsus, Delft University of Technology, Deft, The Netherlands, [email protected] J. Kruithof, Wetsus, The Netherlands M. Van Loosdrecht, Delft University of Technology, Deft, The Netherlands M. Johns, University of Cambridge, Cambridge, UK

High quality drinking water can be produced with membrane filtration processes like reverse osmosis and nanofiltration. A disadvantage of membrane filtration processes is membrane fouling, resulting in higher costs. A major fouling type is biofouling caused by biofilm accumulation in membrane elements [1]. Biofouling development in time is difficult to study because of the construction of spiral wound membrane modules. There is a need for in-situ non destructive quantitative measurements on the accumulation of biomass in spiral wound membranes. Nuclear magnetic resonance (NMR) is a potential powerful tool to study membrane fouling, since it is a quantitative potentially, real-time, non-invasive measurement/imaging technique that is readily applied to opaque samples.

The objective of this study was thus to determine if NMR is a suitable technique to study biofouling of spiral wound membranes.

Biofilm development and velocity distribution images were determined using an appropriate NMR spectrometer as a function of time in a spiral wound membrane module and a flow cell containing spacers and membranes. The flow cell had the same construction as the membrane fouling simulator [3], utilizing sheets of membrane and spacers. The development of pressure drop in time was monitored and the accumulated material on the membranes was analyzed for fouling diagnosis. The feed water was supplemented with a biodegradable compound to stimulate biofilm formation.

The presented NMR protocols allow (i) the extraction of the spatial biofilm distribution in the membrane module, (ii) the velocity field and its evolution with biofouling and (iii) propagators, that is distributions of molecular displacement of a passive tracer (e.g. salts, organic molecules) in the membrane module. Despite the opaque nature of the membrane design, NMR provides a non-invasive, non-destructive and spatially resolved in-situ measurement of biofouling and its impact on hydrodynamics and mass transport. In a spiral wound membrane module, biofilm accumulation and velocity fields were observed over time. Biofilm

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accumulation had a strong effect on the velocity distribution profile. The pressure drop measurements and membrane autopsy confirmed that membrane biofouling occurred. In a flow cell containing feed spacer and membranes, biofilm accumulation and a strong change in velocity distribution was observed as well. The observations of the NMR biofilm imaging matched the visual observations using the sight glass of the membrane fouling simulator, which emphasis the potential of NMR in membrane (bio)fouling studies. Limited biofilm accumulation had great impact on the velocity distribution profile. The measured channeling of the water flow in the NMR studies matched visual observations during membrane autopsies. NMR was thus able to measure the biofilm development and the effect of biofilm formation on the velocity profile.

In summary, NMR is an ideal tool to non- invasively study biofouling development in spiral wound membranes. The NMR enables in-situ real- time non-invasive quantitative measurements for (combinations of) 2D/3D imaging, velocity imaging, and propagators [2].

Literature

[1] Ridgway, H.F. (2003). Biological fouling of separation membranes used in water treatment applications, AWWA research foundation.

[2] Graf von der Schulenburg, D.A., Vrouwenvelder, J.S., Creber, S.A., Van Loosdrecht, M.C.M., Gladden L.F., Johns, M.L. (to be submitted). Nuclear Magnetic Resonance microscopy studies of membrane biofouling.

[3] Vrouwenvelder, J.S. van Paassen, J.A.M., Wessels, L.P., van Dam A.F., Bakker, S.M. (2006). The Membrane Fouling Simulator: a practical tool for fouling prediction and control. Journal of Membrane Science. 281, 316-324.

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Nanofiltration and Reverse Osmosis II - Imaging and Characterization – 4

Tuesday July 15, 10:30 AM-11:00 AM, Maui

Probing Polyamide RO membrane Surface Charge, Energy, and Potential With Advanced Contact Angle Titrations

G. Hurwitz (Speaker), University of California, Los Angeles, Los Angeles, CA, USA E. Hoek, University of California, Los Angeles, Los Angeles, CA, USA, [email protected]

Contact angle titrations are performed to evaluate surface charge, surface tension, and surface potential of a polyamide reverse osmosis (RO) membrane. Contact angle titration involves measuring equilibrium contact angles for both buffered and unbuffered aqueous drops over a range of pH values. The buffered titration gives the fractional ionization of surface functional groups and the effective pKa. The unbuffered titration gives the maximum surface charge density of the membrane. These measured parameters are then combined with the Grahame equation to estimate the membrane surface (zeta) potential. Zeta potentials calculated from the contact angle titrations compare well with those calculated from streaming potential measurements across a range of ionic strength and pH values.

In addition to direct surface titrations, contact angles of a non-aqueous polar liquid and an apolar liquid are measured to enable calculation of Lifshitz-van der Waal, electron-donor, and electron-acceptor surface tensions. These contact angle measurements are augmented by measured contact angles of various aqueous electrolytes to provide further insight into how specific ion interactions influence electron-donor/acceptor components of surface tensions for polyamide RO membranes. The polyamide membrane becomes more hydrophilic as NaCl concentration increases from 0 to 1 M. The higher hydrophilicity results from a larger ratio of electron-donor to electron-acceptor functionality being expressed as the contact angle droplet ionic strength increases. Hydrophilicity also increases with increasing solution pH and in the presence of a few millimoles of divalent cations. However, there are no discernable differences among calcium, barium, magnesium, and strontium at a fixed concentration.

In summary, these results suggest that contact angle analyses can be used to probe membrane surface chemistry to a greater degree than is traditionally pursued. Contact angle titrations may be combined with multiple probe liquid contact angle analyses to elucidate membrane surface charge, tension, and potential. In a more practical sense, the polyamide membrane evaluated becomes more hydrophilic as pH, ionic strength, and minerals content increase. Increased membrane hydrophilicity will no doubt have significant impacts on membrane transport and surface fouling phenomena. Additional research is needed to determine if this behavior is reproducible for other RO membranes

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and, if so, to develop correlations between solution chemistry, membrane properties, and membrane performance.

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Nanofiltration and Reverse Osmosis II - Imaging and Characterization – 5

Tuesday July 15, 11:00 AM-11:30 AM, Maui

Removal of Emerging Organic Contaminants by High-Pressure Membranes: Mechanisms, Monitoring, and Modeling

J. Drewes (Presenting), Colorado School of Mines, Golden, CO, USA C. Bellona, Carollo Engineers, Broomfield, CO, USA M. Sonnenberg, Colorado School of Mines, Golden, CO, USA

The rejection of emerging organic micropollutants is an important issue where recycled water is used to augment drinking water supplies. The focus of this research study was to explore alternatives of an integrated membrane system involving nanofiltration (NF) and ultra-low pressure reverse osmosis (ULPRO) in place of conventional reverse osmosis (RO) representing a more cost-effective system because of potentially lower pressure requirements and the greater selectivity for organic micropollutants as compared to removal of total dissolved solids (TDS).

The organic micropollutants studied in this research included disinfection by-products (e.g., trichloroacetic acid, chloroform, bromoform, N-nitrosodimethylamine), pesticides, endocrine disrupting compounds (e.g., 17²-estradiol, testosterone, bisphenol A), pharmaceutical residues (e.g., ibuprofen, naproxen, gemfibrozil, carbamazepine, primidone), and chlorinated flame retardants. These compounds have a broad range of physicochemical properties, and are associated with potential adverse effects for human health and aquatic life. Uncertainty regarding the rejection of certain solutes, justifies the development of modeling approaches to predict the removal of contaminants by RO and NF. A successful predictive model would eliminate the need for pilot-scale evaluation of trace organic contaminant removal, and eliminate uncertainty regarding permeate water quality. After pre-screening over 15 potential NF and ULPRO products during laboratory-scale membrane rejection experiments, three candidate membranes were selected and pilot tested using a 68 L/min membrane pilot skid for at least 1,300 hours on microfiltered feed water at two full-scale facilities. State-of-the-art membrane characterization tools were used to describe the fouling behavior of NF/ULPRO membranes and determine the role of fouling on operation (e.g., flux decline) and rejection.

Past studies on modeling membrane performance have resulted in several methods and sets of equations that can be used to model the rejection of inorganic and organic solutes. However, simple yet robust solution-diffusion models do not directly apply to membranes in which pore phenomena including physical sieving and Donnan exclusion are important for solute rejection. Transport equations developed to describe the transport of electrolytes through

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non-porous and porous membranes are often hindered by the complexity of the calculations as well as the numerous descriptive parameters required. Although significant advances in membrane modeling have been made in order to optimize the separation of mixtures of inorganic ions and ionic organic solutes, little work has been conducted to satisfactorily quantitatively predict the rejection of organic solutes. Rejection studies at laboratory-, pilot- and full-scale were developed into a model framework to reliably predict - a priori - rejection of organic micropollutants by RO, NF and ULPRO membranes taking into account physicochemical properties of solutes and membranes as well as key operational conditions affecting solute rejection.

Findings of this research clearly demonstrated that a single model does not currently exist that is capable of describing the mass transport of organic micropollutants during high-pressure membrane treatment. Since physicochemical properties of the solutes are the key factors determining rejection, they need to be properly considered and put in context with relevant membrane properties so that rejection can be quantitatively predicted. A number of approaches were assessed to quantitatively describe and predict the rejection of non-ionic and ionic compounds of concern: Spiegler-Kedem model, hydrodynamic model, extended Nernst-Planck equation model(s), and hybrid models combining statistical approaches with membrane transport models. The Spiegler-Kedem model and hydrodynamic model were determined to be only marginally accurate for describing the rejection of a wide variety of non-ionic solutes by a conventional RO, an ULPRO and an NF membrane. However, predictive accuracy was improved by using statistical approaches to determine model parameters as a function of solute properties. For ionic solutes, the Spiegler-Kedem model underpredicted rejection as expected since electrostatic and dielectric exclusion are difficult to integrate into the model. A linearized version of the Donnan Steric Pore model was more suitable for modeling transport of ionic solutes and preliminary results suggest that this modeling approach describes rejection for ionic micropollutants more accurately.

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Nanofiltration and Reverse Osmosis II - Imaging and Characterization – 6

Tuesday July 15, 11:30 AM-12:00 PM, Maui

Evidence of Change in the Top Surface Layer Structure of Nanofiltration Membranes Due to Operating Temperature Variation

H. Saidani, Ecole Nationale des Ingénieurs de Tunis, France B. Nihel, Ecole Nationale des Ingénieurs de Tunis, France P. John, Université Paul Sabatier, France D. Andre (Speaker), Université Montpellier 2, France, [email protected]

The applications of nanofiltration (NF) in the treatment of water and wastewater is developing very quickly. Of special concern for this application is the influence of temperature on the performances of NF membranes, because water to be treated can be at temperatures higher than 40°C. The temperature effect is not yet well understood [1] and is usually described through a simple correction factor applied to the water permeability. The present report shows the influence of operating temperature variation on the permeability and the rejection of neutral and charged solutes. Two commercial NF membranes were used in the course of this study, the DESAL DK (GE Water Technologies -USA) and NF90 (Dow / Filmtec - USA).

The results obtained show an important variation of membrane performances with temperature change both in terms of flux and rejection. Interestingly, while the DESAL DK exhibits the expected flux increase (due to a decrease in solution viscosity) and rejection decrease with increasing temperature, the NF90 shows the opposite trend. Moreover, it was observed that this variation becomes irreversible if the operating temperature exceeds a critical temperature (Tc), which depends on the membrane type.

To understand these phenomena, the thermal behavior of the top surface layer for each NF membrane was investigated. It was found that Tc corresponds to the glass transition temperature Tg of the polymer constituting the membrane top active layer. The pore size and effective layer thickness were estimated using the Nanoflux® NF modeling software [2].

The NF data are interpreted in terms of structural changes occurring during temperature cycles that are intimately related to the intrinsic thermal properties of the polymeric materials.

[1] Nihel Ben Amar, Hafedh Saidani, André Deratani, John Palmeri, Effect Of Temperature On The Transport Of Water And Neutral Solutes Across Nanofiltration Membranes, Langmuir 23, 2937 (2007).

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[2] Palmeri, J., Sandeaux, R. Sandeaux, X. Lefebvre, P. David, C. Guizard, P. Amblard, J.F. Diaz, B. Lamaze, Modeling of multi-electrolyte transport in charged ceramic and organic nanofilters using the computer simulation program NANOFLUX, Desalination 147 231 (2002).

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Nanofiltration and Reverse Osmosis II - Imaging and Characterization – 7

Tuesday July 15, 12:00 PM-12:30 PM, Maui

Characterization of the Polyamide Active Layer in NF/RO Membranes Using Gold Nanoparticles

F. Pacheco (Speaker), Stanford University, Stanford, CA, USA, [email protected] M. Reinhard, Stanford University, Stanford, CA, USA J. Leckie, Stanford University, Stanford, CA, USA

The goal of this project was to investigate the deposition of nanoparticles during filtration to better understand how transport and rejection mechanisms occur within the active layer of a RO membrane. The active layer in state of the art RO membranes consists of cross-linked networks of fully aromatic polyamide, with an average thickness of approximately 200 nm and a very heterogeneous structure that confers the membrane a relatively rough surface, also described in the field as the peak-and-valley structure. Because of the thinness of this layer, characterization at the microscale is extremely difficult and as result knowledge of the transport and separation mechanisms is incomplete. Experiments were performed with gold nanoparticles in a dead-end filtration system without stirring at a pressure of 4.8 bar (70 psi). The membrane investigated was a commercial low pressure RO membrane with a fully aromatic polyamide layer featuring the characteristic peak- and-valley rough structure.

The ability to separate the polyamide layer from the underlying polysulfone support was used to develop a novel TEM based technique that allowed us to image the spatial distribution of the gold nanoparticles with respect to the projected surface area of the polyamide layer. The resulting images show that the particles did not accumulate uniformly over the surface of the membrane, but instead formed distinct clusters around the areas where the polyamide layer was the thickest, i.e. the areas near the peaks. TEM images of polyamide cross sections, as well as SEM images of the membrane surface, confirmed that the particles accumulated preferentially on the peaks rather than in the valleys of the polyamide structure. Although the deposited nanoparticles only covered about 30% of the projected surface area of the membrane, water flux was significantly reduced. These results suggest that there are areas within the polyamide layer that have higher permeability to water and that are the most sensitive to fouling. The effects of particle size and concentration, pH and ionic strength were investigated.

The use of nanoparticles in combination with advanced microscopic imaging techniques can be used to examine which sections of the polyamide layer in NF and RO membranes are actively involved in the transport and rejection mechanisms, as well as those that are highly sensitive to the initial stages of

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fouling. Information obtained from these experiments can also be useful to better understand how membranes will perform with feeds containing other kinds of nanoparticles.

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Nanostructured Membranes II – 1 – Keynote

Tuesday July 15, 8:15 AM-9:00 AM, Moloka’i

Nanofiltration of Electrolyte Solutions by Sub-2nm Carbon Nanotube Membranes

F. Fornasiero (Speaker), Lawrence Livermore National Laboratory, Livermore CA, USA, [email protected] H. Park, Lawrence Livermore National Laboratory, Livermore CA, USA J. Holt, Lawrence Livermore National Laboratory, Livermore CA, USA M. Stadermann, Lawrence Livermore National Laboratory, Livermore CA, USA S. Kim, University of California at Davis, Davis, CA, USA J. In, University of California at Berkeley, Berkeley, CA, USA C. Grigoropoulos, University of California at Berkeley, Berkeley, CA, USA A. Noy, Lawrence Livermore National Laboratory, Livermore CA, USA O. Bakajin, Lawrence Livermore National Laboratory, Livermore CA, USA

MD simulations have shown that liquid and gas flow through carbon nanotubes with nanometer size diameter is exceptionally fast compared to the predictions of continuum hydrodynamic theories and, also, compared to conventional membranes with pores of similar size, such as zeolites. This unique property has been attributed to their exceptionally smooth pore walls allowing nearly frictionless transport, and to fluid molecular ordering at nanoscale. Recently, the availability of membranes made of well-aligned carbon-nanotube (CNT) arrays embedded in an impermeable filling matrix has allowed experimental confirmation of MD predictions on a laboratory scale. For applications in separation technology, selectivity is required together with fast flow. In particular, for water desalination, coupling the enhancement of the water flux with selective ion transport could drastically reduce the cost of brackish and seawater desalting.

In this study, we use pressure-driven filtration experiments, coupled with capillary electrophoresis analysis of permeate and feed to quantify ion exclusion in silicon nitride/CNT composite membranes as a function of solution ionic strength, pH, and ion valence. The pores of the membranes used in this study are sub-2-nm diameter CNTs whose entrance is decorated by negatively charged carboxylic groups.

We show that carbon nanotube membranes exhibit significant ion exclusion that can be as high as 98% under certain conditions. Our results support a Donnan-type rejection mechanism, dominated by electrostatic interactions between fixed membrane charges and mobile ions, while steric and hydrodynamic effects appear to be less important. Comparison with commercial nanofiltration membranes for water softening reveals that our carbon nanotube membranes provides far superior water fluxes for similar ion rejection capabilities.

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This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. UCRL-ABS-236106

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Nanostructured Membranes II – 2

Tuesday July 15, 9:30 AM-10:00 AM, Moloka’i

Aligned Carbon Nanotube Membranes: Transport Enhancement and Gatekeeper Activity

M. Majumder, Univ. of KY, Lexington KY, USA K. Kiess, Univ. of KY, Lexington KY, USA J. Wu, Univ. of KY, Lexington KY, USA B. Hinds (Speaker), Univ. of KY, Lexington KY, USA, [email protected]

Carbon nanotubes have three key attributes that make them of great interest for novel membrane applications 1) atomically flat graphite surface allows for ideal fluid slip boundary conditions 2) the cutting process to open CNTs inherently places functional chemistry at CNT core entrance and 3) CNT are electrically conductive allowing for electrochemical reactions and application of electric fields gradients at CNT tips. Towards this goal, a composite membrane structure containing vertically aligned carbon nanotubes passing across a polystyrene matrix film have been fabricated. Fabrication steps, material characterization and ionic diffusion transport properties are described. Plasma oxidation during the fabrication process introduces carboxylic acid groups on the CNT tips that are modified using carbodiimide mediated coupling between carboxylic acid on the CNTs and accessible amine groups of the functional molecule. To explore the hypothesis of “Gatekeeper” selectivity, the entrances to CNT’s cores were functionalized with aliphatic amines of different lengths, charged dye molecule and an aliphatic amine elongated by spacers containing poly-peptides. The simultaneous permeation of two differently sized but equally charged molecules (ruthenium bi-pyridine [Ru-(bipy)3

+2] and methyl viologen [MV+2]) was studied and relative selectivity of was seen to vary from 1.9 to 3.6 as a function of tip-functionalization chemistry. Anionic charged functional groups are seen to sharply increase flux of cationic permeates. This effect is reduced at higher solution ionic strength consistent with shorter Debye screening length screening attractive charge at the CNT core entrance. Using a hindered diffusion to model observed selectivities was consistent only with a geometry of only CNT tip functionalization, not along the length of CNT core. Bio-chemical gating of CNTs is also seen by tethering desthiobiotin to CNT tips with the reversible binding to streptavidin. The complete ATP cycle (phosphylation/dephosphylation) can be performed on CNT tips with corresponding modulation of flux across CNT membrane. Strong electrostatic effects of binding protein are seen with enhanced cationic flux seen for the relativel open anioic protein binding at CNT tip entrance. The functional density of tethered charge molecules can be substantially increased by the use of electrochemical grafting of diazonium salts. Functionality can be forced to occur at the CNT tip entrances by fast fluid flow of an inert solvent through the core during electrochemical functionalization. The selectivity

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between Ru(bi-pyridine)32+ and methyl viologen 2+ flux is found to be as high as

23 with -130mV bias applied to the membrane with tethered anionic dye molecule. Changes in the flux and selectivity support a model where charged tethered molecules at the tips are drawn into the CNT core at positive bias hindering/gating flux across the membrane. Applications towards controlled transdermal drug delivery are discussed. In general, the transport mechanisms through CNT membrane are a) ionic diffusion is near bulk expectation with no enhancement from CNT b) gas flow is enhanced by ~1-2 order of magnitude due to specular reflection off of flat graphitic surface c) and pressure driven flux of a variety of solvents (H2O, hexane, decane ethanol, methanol) are 4-5 ORDERS OF MAGNITUDE FASTER than conventional Newtonian flow due to atomically flat graphite planes inducing nearly ideal slip conditions.

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Nanostructured Membranes II – 3

Tuesday July 15, 10:00 AM-10:30 AM, Moloka’i

Hybrid Biomimetic Membranes: Past, Present and Beyond

M. Barboiu (Speaker), Institut Europeen des Membranes, France, [email protected]

Many fundamental biological processes appear to depend on unique properties of molecular recognition or self-assembled domains of the biomolecules. Such behaviour is illustrated by the functional complexity of self-organized membrane proteins, which may assist in proton and ion translocation through membranes. Gramicidin A and KCsA K+ ionic channels, Aquaporin water channels are well known non-exclusive examples of functional systems in which protons, ions and water molecules are envisioned to diffuse along a directional pathways according to different relaying and migration mechanisms. Numerous artificial transport systems utilizing carriers, channel-forming or self-organized polymeric superstructures able to orient, to select and to pump the ionic transport across membranes have been developed in the last decades. Artificial membrane materials are the subject of various investigations, offering great potentialities as well on the level of their chemical composition or organization as to that of the concerned applications. Of special interest is the structure- directed function of biomimetic and bioinspired membrane materials and control of their build-up from suitable units by self-organisation. The main interest focus on functional biomimetic membranes in which the recognition-driven transport properties could be ensured by a well-defined incorporation of receptors of specific molecular recognition and self-organization functions, incorporated in a hybrid dense or mesopourous materials. We are therefore proposing to review the membrane facilitated transport properties of such supramolecular membrane materials. The first part begins with a survey of different methods and processes which can be used for the generation of molecular recognition-based hybrid materials. Then basic working principles of self-organized membranes are provided in order to better understand the requirements in material design for the generation of functional membrane materials.These results describe the simple synthetic hybrid biomaterials which successfully formed molecular recognition devices, transport patterns so as to enable efficient translocation events. Finally actual and potential applications of such self-organized systems presenting combined features of structural adaptation in a specific nanospace will be presented. From the conceptual point of view these membranes express a synergistic adaptative behaviour: the addition of the fittest solute drives a constitutional evolution of the membrane toward the selection and amplification of a specific transporting superstructure in the presence of the solute that promoted its generation in a first time. This is the interesting example of dynamic evolutive membranes, where a solute induces the upregulation of (prepares itself) its own selective membrane.

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[1] M. Barboiu, C. Luca, C. Guizard, N. Hovnanaian, L. Cot, G. Popescu, J. Membrane Sci., 1997, 129, 197-207.

[2] M. Barboiu , N. Hovnanian, C. Luca, L. Cot, Tetrahedron, 1999, 55, 9221-9232.

[3] M. Barboiu, C. Guizard, J. Palmeri, C. Reibel, C. Luca, L. Cot, J. Membrane Sci. 2000, 172, 91-103.

[4] C. Guizard, A. Bac, M. Barboiu, N. Hovnanian, Sep. Tech. Pur. 2001, 25, 167-180.

[5] M. Barboiu, G. Vaughan, A. van der Lee, Org. Lett. 2003, 5, 3073-3076.

[6] M. Barboiu, J. Incl. Phenom. Mol. Rec. 2004, 49, 133-137.

[7] M. Barboiu, S. Cerneaux, G. Vaughan, A. van der Lee, J. Am. Chem. Soc. 2004, 126 3545-3550.

[8] C. Arnal-Herault, M. Barboiu, E. Petit, M. Michau, and A. van der Lee, New J. Chem., 2005, 29, 1535-1539.

[9] A. Cazacu, A. Pasc-Banu, M. Barboiu, Macromol. Symposia, 2006, 245-246, 435-438.

[10] A. Cazacu, C. Tong, A. van der Lee, T.M. Fyles, M. Barboiu, J. Am. Chem. Soc. 2006, 128(29), 9541-9548.

[11] C. Arnal-Herault, A. Pasc-Banu, M. Michau, M. Barboiu, Angew. Chem. Int. Ed. 2007, 46, 8409- 8413.

[12] C. Arnal-Hérault, M. Barboiu, A. Pasc, M. Michau, P. Perriat, A. van der Lee, Chem. Eur. J. 2007, 13, 6792

[13] M. Michau, M. Barboiu, R. Caraballo, C. Arnal- Hérault, A. van der Lee, Chem. Eur.J. 2007, in press.

[14] C. Arnal-Herault, A. Pasc-Banu, M. Barboiu A. van der Lee, Angew. Chem. Int. Ed. 2007, 46, 4268-4272.

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Nanostructured Membranes II – 4

Tuesday July 15, 10:30 AM-11:00 AM, Moloka’i

Nanostructured Polymers with Uniform d1 nm Pores Based on Cross-linked Lyotropic Liquid Crystals for Molecular Size-Selective Separations

D. Gin (Speaker), University of Colorado at Boulder, Boulder, CO, USA, [email protected] M. Zhou, University of Colorado at Boulder, Boulder, CO, USA X. Lu, University of Colorado at Boulder, Boulder, CO, USA E. Hatakeyama, University of Colorado at Boulder, Boulder, CO, USA R. Noble, University of Colorado at Boulder, Boulder, CO, USA B. Elliott, TDA Research, Inc., Wheat Ridge, CO, USA

The ability to fabricate porous polymer membrane materials that can separate molecular mixtures cleanly based solely on differences in molecular size or shape is one of the long-sought after goals in membrane science. The design of ordered, nanoporous polymers based on cross-linked lyotropic (i.e., surfactant) liquid crystals (LLCs) for molecular size-selective separations of gases and aqueous solutions will be presented. First-generation LLC membranes of this type are based on an inverted hexagonal (HII) phase architecture and contain monodisperse, ionic, cylindrical channels that are ca. 1.2 nm in diameter. Supported HII membranes are able to completely reject water-soluble molecules and ions greater than or equal to the nanopore diameter, allowing them to cleanly separate molecular mixtures straddling this size threshold. The same HII materials copolymerized with butyl rubber afford highly selective, "breathable" vapor barrier materials for chemical warfare agent protection. They exhibit good water vapor permeability but are still able to reject mustard agent simulants to a large degree, whereas pure cross-linked butyl rubber shows slightly lower chemical warfare agent simulant permeability and no water vapor transport. Preliminary studies also showed that these HII polymers have interesting sorption and permeation properties for light gases that are dependent on the nanostructure. The only caveats with these first-generation LLC membranes is that (1) they exhibit low water flux due to lack of control over bulk alignment of the cylindrical nanopores; and (2) they have nanopores that are too large to reject solutes smaller than 1 nm in size. More recently, second-generation cross-linked LLC materials based on a bicontinuous cubic (Q) phase have been developed that contain a 3-D interconnected water layer manifold system with a uniform gap size of less than 1 nm. These LLC membranes are able to cleanly size-exclude hydrated salt ions and small organic solutes < 1 nm in size from water with good permeabilities and excellent performance stability. The potential of these unique, sub-1-nm ultrafiltration materials for biologically relevant separations will be discussed. LLC-butyl rubber composite membranes based on this Q-phase material also show over an order of magnitude improvement in water vapor flux, and water vs. chemical warfare agent simulant selectivity, compared to the first-generation HII-phase materials.

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Nanostructured Membranes II – 5

Tuesday July 15, 11:00 AM-11:30 AM, Moloka’i

Track-Etched Polymer Membranes as Tool to Investigate Grafted Stimuli-Responsive and Other Functional Polymers for ‘Smart’ Nano- and Microsystems

M. Ulbricht (Speaker), Lehrstuhl für Technische Chemie II, Universität Duisburg-Essen, Germany, [email protected] A. Friebe, Lehrstuhl für Technische Chemie II, Universität Duisburg-Essen, Germany F. Tomicki, Lehrstuhl für Technische Chemie II, Universität Duisburg-Essen, Germany

There is an increasing scientific and technical interest in the functionalization of materials surfaces with thin grafted polymer layers. The focus in this field is now on synthesis methods which allow a precise control of grafted layer architecture (grafting density, grafted chain length at low polydispersity, type and distribution of functional groups), and on the detailed evaluation of correlations between structure and properties of such functional polymer layers. In the recent years, our group has systematically explored track-etched membranes (TEM) from poly(ethylene terephthalate) (PET) as versatile base materials to investigate various surface functionalization chemistries and the consequences for composite material’s functions, such as selective barrier, selective adsorber or catalytic reactor [1]. More recently, we have demonstrated that with a comprehensive characterization of the pore structure of an isoporous base membrane (pore diameter and pore density from combination of SEM analysis, gas flow / pore dewetting permporometry and liquid permeability under well-defined conditions) as basis, and the confirmation of even coverage of the entire membrane (pore) surface (from contact angle and trans-membrane zeta potential measurements), the effective grafted layer thickness (in the range of a few to several hundreds nanometers) under different conditions (e.g., pH, temperature) can be deduced from liquid permeability data [2].

Here we will focus on our recent work on surface- initiated atom transfer radical polymerization (ATRP) within the pores of PET TEM (pore diameters between 100 and 1000 nm). In our first paper on that topic [3], we had confirmed that grafted temperature-responsive poly-N- isopropylacrylamide (PNIPAAm) with a “brush” structure (polymer density in swollen state ~0.4 g/cm3, swelling / deswelling ratios of ~3) has been achieved, and that a reduction of grafting density was possible via the conditions during solid-phase synthesis for introduction of the ATRP initiator (this leads to lower polymer densities and higher swelling / deswelling ratios). The reaction conditions for ATRP had been optimized so that ‘living’ polymerization is now established for NIPAAm and various other functional monomers (e.g., tert.- butyl acrylate /tBA/, N,N-dimethylaminoethyl methacrylate, or polyethyleneglycol methacrylate), and this is

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confirmed by highly efficient re- initiation and successful synthesis of block copolymers (at preserved high polymer density in swollen state). Influences of membrane pore diameter, grafting density and chain lengths are currently systematically investigated, and the results will be discussed and compared with data of other groups who use non-porous SAM-coated planar inorganic or metal substrates. The potential of the obtained systems as functional devices will also be illustrated. For example, by combining temperature-responsive PNIPAAm with pH- responsive poly(acrylic acid) (as grafted block copolymers, prepared via grafted poly(tBA)), membrane pores with four distinctly different effective pore sizes as function of the combination of temperature (25°C vs. 40°C) and pH (2 vs. 7) could be prepared, and those membranes were evaluated with respect to their barrier properties in diffusion and filtration experiments.

In conclusion, we will demonstrate that the pore space of membranes can be controlled by grafted functional polymer layers having densities and thicknesses (between a few to several 100s nanometers), which are pre-determined by well- defined ‘grafting-from’ reactions such as surface- initiated ATRP. An important feature is the response of those layers to stimuli, and this can be used to create ‘gates’ or ‘valves’ in the nano- or microscale. The binding to functional groups in those layers (e.g., immobilization or reversible binding of biomolecules) provides additional attractive options. The knowledge gained from our model studies with TEM on the correlations between synthesis, structure and function of such tailored grafted polymer layers can be transferred to other porous membranes, and this will enable the preparation of novel membrane-based materials for advanced separations, controlled release, catalysis and other applications.

[1] M. Ulbricht, Polymer 2006, 47, 2217-2262.

[2] C. Geismann, A. Yaroshchuk, M. Ulbricht, Langmuir 2007, 23, 76-83.

[3] A. Friebe, M. Ulbricht, Langmuir 2007, 23, 10316-10322.

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Nanostructured Membranes II – 6

Tuesday July 15, 11:30 AM-12:00 PM, Moloka’i

Fixed-Charge Group-like Behavior of the Captured Ion By Crown Ether and Its Effect on the Response of a Molecular Recognition Ion Gating Membrane

T. Ito (Speaker), Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama, Japan T. Yamaguchi, Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama, Japan, [email protected]

We have suggested the concept of a molecular recognition ion gating membrane, which can open and close its pores automatically in response to the specific ion signals such as Ba2+ and K+, and have showed various functions of the gating effect to control pressure-driven permeation, osmotic pressure, and diffusion. These response behaviors of the gating membrane mainly depend on the swelling and shrinking of the grafted poly- NIPAM(N-isopropylacrylamide)-co-BCAm (Benzo- [18]-crown-6-acrylamide). The grafted copolymer have crown ether moieties, which can capture specific ion species and trigger the swelling of the grafted polymer. This swelling and shrinking of the grafted copolymer also accompany the change of water hydration onto the copolymer. These phenomena were thought to control the membrane responses. However, we recently found some interesting gating behaviors, which can’t be explained by swelling and shrinking only. For instance, the permeability change of a small molecular weight drug in response to ion stimulations was larger than that of high molecular weight drug. The difference between these drugs was whether the drugs have charges or not. Second, ion concentration gradient through the gating membrane generated osmotic pressure, even though the size of ions was small enough and water content of the grafted copolymer was high enough. Based on these phenomena, the captured ions by crown ether moieties behave like fixed- charge groups, and the molecular recognition ion gating membrane has the aspect of a charged membrane, which can change its fixed charge density in response to the specific ion signals. We conclude that combination of hydration effect and charge effect of the grafted copolymer can make the sophisticated functions of the molecular recognition ion gating membrane.

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Nanostructured Membranes II - 7

Tuesday July 15, 12:00 PM-12:30 PM, Moloka’i

Multifunctional ultrathin TiO2 Nanowire Ultrafiltration Membrane for Water Treatment

X. Zhang (Speaker), Nanyang Technological University, Singapore A. Du, Nanyang Technological University, Singapore J. Pan, Nanyang Technological University, Singapore D. Sun, Nanyang Technological University, Singapore, [email protected] J. Leckie, Stanford University, Stanford, CA, USA

For the last two decades, micro/ultra filtration membranes have been used as an advanced water treatment process for producing high quality drinking water with small footprint1. Recently, inorganic membranes have attracted considerable attention due to their excellent thermal, chemical, mechanical stability 2. Among the materials used for the preparation of inorganic membranes, TiO2 is unique due to its excellent performance under UV irradiation on mineralization of virtually all organic compounds 3, 4. So, TiO2 membrane can provide concurrent filtration and photocatalytic oxidation. Recently various morphologies of 1 dimensional (1D) nanostructured TiO2, including nanowires, nanofibers, nanorods and nanotubes, have been prepared by means of chemical or physical methods 5-11. These nanostructured TiO2 photocatalysts exhibit superior photocatalytic efficiency relative to conventional bulk materials as a result of its larger surface area and presence of quantum size effect.

In this paper, a new kind of multifunctional ultrathin TiO2 nanowire UF membrane was fabricated using a method of hydrothermal syntheses-filtration. The fabricated UF membrane has a supporting layer of glass fiber and a funcational layer of ultrafine TiO2 nanowire. These TiO2 nanowires had typical diameter of several micrometers. Beside of good performance on separation, the TiO2 membrane exited excellent photocatalytic activity on degradation of methylene blue (MB). The nanowire membrane has shown unusual potentials for environmental purification.

Ultrathin TiO2 nanowires were systhesized by hydrothermal reaction. These TiO2 nanowires were assembled on glass filter by filtration with surfactant assistant. The photocatalytic activity of the TiO2 nanowire membrane were evaluated with MB and humic acid (HA) as model pollutants.

FESEM observation revealed that the TiO2 nanowire functional layer of the membrane was formed by overlap and interpenetration of long TiO2 nanowires with typical lengths of several micrometers. The surface of membrane was very flat. TEM observations revealed that the diameters of TiO2 nanowires were less

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than 10 nm. XRD data suggest that the crystal phase of TiO2 nanowire depends on the calcination temperature. The pure anatase phase (JCPDS 21-1272) was gained at 600 °C.

From the FESEM images of the TiO2 nanowire membrane, the size of pore formed in the functional layer is less than 10 nm suggesting that it was an UF membrane. The MWCO of the TiO2 nanowire membrane was determined with different molecular weight of PEG (400, 1K, 4K, 6K, 10K and 35K). According to the results of filtration, the MWCO of the TiO2 nanowire of membrane was about 10K.

The photocatalytic activity of TiO2 nanowire membrane was evaluated by the photocatalytic oxidation of MB under UV irradiation. Finger prints of aqueous MB (1.0 × 10-4 mol/L) were made onto the TiO2 nanowire membrane and a commercial glass fiber membrane. Both membranes were exposed to UV irradiation. After 30 min of irradiation, no remarkable change was found to the mark on the SiO2 fiber membrane. However, the MB mark on TiO2 nanowire membrane completely disappeared, which indicated that the TiO2 nanowire membrane has good photocatalytic activity.

To investigate the concurrent capacity of separation and photocatalytic oxidation of the TiO2 nanowire membrane, HA solution of 20 mg/L was filtered using the TiO2 nanowire membrane in continuous operation mode under UV irradiation. The membrane flux was kept a constant for a long time. The removal rates of HA and TOC by the two processes are almost 100% abd 95.1%, respectively. It clearly indicates excellent performance on concurrent filtration and photocatalytic degradation.

Reference

1. Cho, J.; Amy, G.; Pellegrino, J. Journal of Membrane Science 2000, 164, (1-2), 89-110.

2. Choi, H.; Sofranko, A. C.; Dionysious, D. D. Advanced Functional Materials 2006, 16, 1067-1074.

3. Hoffmann, M. R.; Martin, S. T.; Choi, W.; Bahnemann, D. W. Chem. Rev. 1995, 95, (1), 69-96.

4. Fujishima, A.; Rao, T. N.; Tryk, D. A. Journal of Photochemistry and Photobiology C: Photochemistry Reviews 2000, 1, (1), 1-21.

5. Jung, J. H.; Kobayashi, H.; van Bommel, K. J. C.; Shinkai, S.; Shimizu, T. Chem. Mater. 2002, 14, (4), 1445-1447.

6. Yao, B. D.; Chan, Y. F.; Zhang, X. Y.; Zhang, W. F.; Yang, Z. Y.; Wang, N. Applied Physics Letters 2003, 82, (2), 281-283.

7. Kasuga, T.; Hiramatsu, M.; Hoson, A.; Sekino, T.; Niihara, K. Langmuir 1998, 14, (12), 3160-3163.

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8. Tian, Z. R.; Voigt, J. A.; Liu, J.; McKenzie, B.; Xu, H. J. Am. Chem. Soc. 2003, 125, (41), 12384-12385.

9. Yoshida, R.; Suzuki, Y.; Yoshikawa, S. Journal of Solid State Chemistry 2005, 178, (7), 2179-2185.

10. Yuan, Z.-Y.; Su, B.-L. Colloids and Surfaces A: Physicochemical and Engineering Aspects 2004, 241, (1-3), 173-183.

11. Chen, Y.; Crittenden, J. C.; Hackney, S.; Sutter, L.; Hand, D. W. Environ. Sci. Technol. 2005, 39, (5), 1201-1208.

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Pervaporation and Vapor Permeation I – 1 – Keynote

Tuesday July 15, 8:15 AM-9:00 AM, Honolulu/Kahuku

Bioethanol Production Using Pervaporation and Vapor Permeation Membranes

I. Huang (Speaker), Membrane Technology & Research, Menlo Park, CA, USA, [email protected] R. Baker, Membrane Technology & Research, Menlo Park, CA, USA L. Vane, The U.S. EPA, Cincinnati laboratory, Cincinnati, OH, USA

Bioethanol production for use as a renewable energy resource is booming driven by climate change concerns and soaring oil prices. Conventional distillation/molecular sieve drying of bioethanol uses about 20% of the energy content of the ethanol produced. Alternative technologies which consume less energy to dehydrate ethanol are of considerable interest to the bioethanol industry. The existing membrane technology for ethanol/water separations uses pervaporation. The first industrial-scale pervaporation unit was installed in Brazil by GFT (now Sulzer Chemtech) in 1982 to dehydrate ethanol from a cane sugar fermentation plant. Despite this early success, pervaporation has not been widely used in bioethanol production, primarily because the membrane modules used were too expensive and were susceptible to slow degradation, leading to excessive replacement costs.

In this paper, the application of pervaporation and vapor permeation to bioethanol membrane separations is described. Novel, low energy process designs require membrane modules able to operate at high temperatures with high water concentration ethanol solutions. The requirements for membrane properties are discussed. The processes described showed significant energy savings compared to the conventional distillation/molecular sieve drying process.

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Pervaporation and Vapor Permeation I – 2

Tuesday July 15, 9:30 AM-10:00 AM, Honolulu/Kahuku

Dewatering Ethanol with Chemically and Thermally Resistant Perfluoropolymer Membranes

S. Majumdar (Speaker), Compact Membrane Systems, Inc., Newport, DE, USA, [email protected] D. Stookey, Compact Membrane Systems, Inc., Newport, DE, USA S. Nemser, Compact Membrane Systems, Inc., Newport, DE, USA

Bio-based ethanol is a renewable energy source. Ethanol from agricultural sources has many potential advantages including development of fuel independence and reduction in greenhouse gas generation. However, the energy costs associated with converting fermentation ethanol to dry fuel grade ethanol are substantial. Ethanol as derived through fermentation from biomass contains a significant amount of water. Dehydration is an essential process step that is complicated by the ethanol-water azeotrope.

CMS is currently investigating highly permeable, chemically and thermally resistant perfluoropolymer membranes to selectively remove water from water-ethanol mixtures. These membranes are hydrophobic and organophobic and yet have high water vapor permeation flux. Basic data in combination with preliminary economic and engineering analysis show that a process scheme that includes CMS membranes can improve the overall economics for dewatering and producing fuel-grade ethanol. This presentation discusses the application of this novel perfluoropolymer membrane-based technology for the production of fuel-grade ethanol.

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Pervaporation and Vapor Permeation I – 3

Tuesday July 15, 10:00 AM-10:30 AM, Honolulu/Kahuku

Modeling and Process Integration of Membranes for Ethanol Dehydration

P. Bösch, Vienna University of Technology, Vienna, Austria, [email protected] P. Schausberger, Vienna University of Technology, Vienna, Austria A. Boontawan, Suranare University of Technology, Institute of Agricultural Technology, Sc, Nakhon Ratchasima, Thailand A. Friedl (Speaker), Vienna University of Technology, Vienna, Austria

To capitalize on economy of scale effects ethanol for fueling vehicles is produced in facilities with a yearly output of >100.000 t/a. Although the plants are economical viable, the ecology of the overall process is in doubt. This is mostly due to the distances the feed crop travels, the fertilizer required during crop cultivation and also on the used energy source for the process. Therefore a feasibility study on small scale ethanol production (<10.000 t/a) is conducted. As part of this effort the dehydration of ethanol has to be reevaluated with regard to membrane technology. Pressure swing adsorption, the state of the art technology for large scale ethanol production, is known to be too complex and expensive for the targeted size of the plant. The work on this task comprises two distinct phases. First a test bench was designed to evaluate a commercial membrane for its performance under different operating conditions (vapor permeation mode at varied feed flow, feed concentration, feed temperature as well as permeate pressure). The experimental data collected (flux data and separation efficiency) were then processed to yield a scalable, semi-empirical model for the mass and heat balances of the separation unit. Second the optimum integration of the membrane dehydration step into an overall ethanol production process was determined by process simulation. For this purpose the membrane dehydration model and models of all other process unit operations (feedstock- pretreatment, ethanol fermentation & distillation, anaerobic digestion, combined-heat-and-power production) were incorporated to the process simulation package IPSEpro software for steady state flowsheet simulation. The emphasis at simulation was put on the heat integration of the overall process. Therefore the interplay of distillation, rectification and the vapor permeation was investigated by varying operation pressures and temperature levels. The results to be presented are detailed data from the dehydration experiments, the derivation and testing of the corresponding unit operation model as well as the overall process model. Based on the later, simulations for different flowsheets will be presented and the operating conditions for minimum energy consumption and membrane area equipment will be derived. The overall outcome will be a technological assessment of membrane technology for ethanol dehydration on the small scale.

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The authors gratefully acknowledge the support by “Energy Systems of Tomorrow”, a subprogram of the Federal Ministry of Transport, Innovation and Technology (BMVIT) in cooperation with the "Austrian Industrial Research Promotion Fund" (FFG).

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Pervaporation and Vapor Permeation I – 4

Tuesday July 15, 10:30 AM-11:00 AM, Honolulu/Kahuku

Performance of a New Hybrid Membrane in High Temperature Pervaporation

H. van Veen (Speaker), Energy research Centre of the Netherlands, ECN, The Netherlands, [email protected] R. Kreiter, Energy research Centre of the Netherlands, ECN, The Netherlands C. Engelen, Energy research Centre of the Netherlands, ECN, The Netherlands M. Rietkerk, Energy research Centre of the Netherlands, ECN, The Netherlands H. Castricum, Univ. of Twente, The Netherlands A. ten Elshof, Univ. of Twente, The Netherlands J. Vente, Energy research Centre of the Netherlands, ECN, The Netherlands

Thermal separation processes like distillation consume a large amount of energy in the process industry. Replacing these processes by membrane pervaporation will lead to much lower energy consumption. The expected high chemical and thermal stability of inorganic membranes compared to polymer membranes has resulted in a growing research activity with the first aim of replacing polymer membranes with inorganic ones. The superior separation performance, i.e. selectivity and flux, of silica-based membranes in the dehydration of alcohols and solvents at elevated temperatures has raised the interest even further. The application depends on a reliable and good long-term performance. Unfortunately, information on this topic is still very limited. We have shown that silica and methylated silica membranes are not stable at temperatures above 100°C and the application window of state-of-the-art Me-SiO2 membranes for use in dehydration processes is limited to 95°C [1]. For methanol separation from organic solvents the Me-SiO2 membranes can be used at higher temperatures [2].

Hybrid silica materials are expected to have a much higher hydrothermal stability than (methylated) silica. The superior separation performance, i.e. selectivity and flux, of these hybrid membranes in the dehydration of alcohols and solvents at elevated temperatures has raised the interest [3]. High flux performance is required to decrease the membrane area needed and thereby the price to become competitive against the well know distillation technique. It is proven that the required water flux of at least 3 kg/m2h, for the dehydration of 5wt.% water in butanol as a representative standard application, can be achieved easily. The profitable application of the membranes depends on a reliable, stable long-term behaviour and the broad applicability especially at temperatures above 100°C. We will report on the development of organic/inorganic hybrid silica membranes with selectivities and fluxes, that are comparable with the silica based membranes in dehydration by pervaporation. Details of test results will be given in different dehydration applications up to 150°C including the dehydration of

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aprotic solvents. Further, results will be given on long term stability testing up to 150°C and up to 2 years of continuous operation in the dehydration of organic mixtures. The results show that a completely new class of hybrid materials is available that opens new markets for dehydration processes by pervaporation.

Acknowledgement Part of this work was supported with a grant from the Dutch Ministry of Economic Affairs via the EOS- LT (Long term energy research subsidy) programme, managed by SenterNovem.

References

[1] J. Campaniello, C.W.R. Engelen, W.G. Haije, P.P.A.C. Pex and J.F. Vente, Long-term performance of microporous methylated silica membranes, Chem.Comm. (2004), p.834-835.

[2] J.F. Vente, H.M. van Veen and P.P.A.C. Pex, Microporous sol-gel membranes for molecular separations, Ann.Chim.Sci.Mat. (2007),Vol. 32, No.2, 231-244.

[3] H.L. Castricum, A. Sah, R. Kreiter, D.H.A. Blank, J.F. Vente and J.E. ten Elshof, Chem.Comm. (2008), DOI:10.1039/B718082A.

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Pervaporation and Vapor Permeation I – 5

Tuesday July 15, 11:00 AM-11:30 AM, Honolulu/Kahuku

Investigation of the Fundamental Differences between Polyamide-imide (PAI) and Polyetherimide (PEI) Membranes for Isopropanol Dehydration via Pervaporation

Y. Wang (Speaker), National University of Singapore, Singapore L. Jiang, National University of Singapore, Singapore T. Chung, National University of Singapore, Singapore T. Matsuura, University of Ottawa, Ottawa, Ontario, Canada S. Goh, National University of Singapore, Singapore

Polyimides (PI) are recently emerging as a promising material for pervaporation dehydration of alcohols because of their excellent thermal, chemical and mechanical stabilities. In this study, two kinds of polyimides, Torlon 4000TF polyamide- imide (PAI) and Ultem 1010 polyetherimide (PEI) membranes are investigated as membrane materials for the pervaporation dehydration of isopropanol. Generally, PAI membranes are found to have higher separation performance than PEI membranes. The physicochemical properties of these two materials and the as-fabricated membranes are investigated and correlated to the pervaporation performance through different characterizations (DSC, TGA, Goniometery, X-ray diffraction, gas permeation, and water sorption). PAI membranes exhibited better pervaporation performance which is attributed to the greater hydrophilicity, higher glass transition temperature, narrower d-space, higher density and higher water uptake. Compared with PEI dense membranes, PAI dense membranes show a much higher separation factor (up to 3000 at 60 °C) and comparable flux. PAI membranes also showed higher O2/N2 selectivity than PEI with comparable gas permeability. The results showed that, for the fabrication of the asymmetric membranes, the dope concentration is a very important factor on its pervaporation performance. For both PAI and PEI membranes, dope concentrations equal to or higher than their critical concentrations are essential to produce useful pervaporation membranes. In addition, heat treatment is an effective way to reduce defects and enhance separation performance. This is because the molecular chain packing of the top dense layer becomes denser with increasing dope concentration or thermal treatment temperature of the membrane. Further increase of the dope concentration or thermal treatment temperature may cause an increased substrate resistance, which leads to the decrease of the selectivity. Pervaporation process using different operation modes is also studied. The separation using a membrane with porous structure facing against the feed solution shows a much higher separation factor with only a slight decrease of flux. This important phenomenon can be explained in terms of the balance

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between two major contradictory effects: concentration polarization and dense layer swelling.

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Pervaporation and Vapor Permeation I – 6

Tuesday July 15, 11:30 AM-12:00 PM, Honolulu/Kahuku

Preparation of Asymmetric Polyetherimide Membranes for Molecular Liquid Separations

A. El-Gendi, LSGC-CNRS, Nancy Université, France D. Roizard, LSGC-CNRS, Nancy Université, France, [email protected] E. Favre (Speaker), LSGC-CNRS, Nancy Université, France

The aromatic polyimides are a well-known class of polymer materials, which have been widely studied for over 20 years in the field of membrane separation. As glassy polymers, they possess remarkable mechanical and chemical properties for organic materials, but in general their permeability coefficients are limited because of their rigid carbon skeleton and low available free volume; hence their application to molecular separation is limited to gas separations.

To circumvent this problem, and to broaden the scope of these very stable polymers, we have studied the properties of a block-ether aromatic polyimide series comprising a flexible block and we prepared asymmetrical films with the aim of achieving liquid-liquid separations. Using various experimental conditions of phase inversion, either totally opened microstructures typical of microfiltration membranes or asymmetric microstructures with a thin dense top surface could be obtained and then tested for the fractionation by pervaporation of model liquid mixtures, such as toluene - heptane or water - ethanol. As an interesting outcome, it was found that some copolyether-imide aromatic membranes could indeed present high permeation fluxes and fairly good selectivities. Thus, it is expected that the development of these new asymmetric block copolyimide membranes might give rise to high performance membrane systems for applications in liquid-liquid separations.

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Pervaporation and Vapor Permeation I – 7 Tuesday July 15, 12:00 PM-12:30 PM, Honolulu/Kahuku

Preparation of a Novel Styrene-Butadiene-Styrene Block Copolymer (SBS) Asymmetric Membrane for VOC Removal by Pervaporation

A. Figoli (Speaker), Institute on Membrane Technology (ITM-CNR), Italy, [email protected] S. Sikdar, USEPA, Cincinnati, OH, USA J. Burckle, USEPA, Cincinnati, OH, USA E. Drioli, Institute on Membrane Technology (ITM-CNR), Italy

Pervaporation (PV) is often applied to the separation of volatile organic chemicals (VOCs) from water. This process provides a cost effective means to achieve the removal of VOC's in the 50 to 150's ppm range concentrating by a factor of 10 to 7000 times or more, permitting recovery in a concentrated form for recycle and reuse or disposal. The economic application of pervaporation is highly dependent upon the efficiencies of the membranes developed for pervaporation applications. Most of the commercial systems use standard polydimethylsiloxane (PDMS) membranes. In literature, PDMS membranes employed in trichloroethane (TCA) removal from water by PV showed a selectivity in the range of 2000-3000 and flux of 15 g/m2 h [1-2]. Other elastomeric polymers such as EPDM (ethylene-propylene-diene) terpolymer, NBR (nitrile butadiene rubber), PEBA (polyether-block-polyamide) have also shown promising results. Sikdar, et al. [3] studied the potentiality of a different material, styrene-butadiene-styrene block copolymer (SBS), for VOCs removal from water. The SBS coated on polymeric material lead to a significant improvement in the selectivity (TCA/H2O) in the range of 3000-5000, while retaining a relatively high flux. On the basis of such results, in this work we report the preparation of novel asymmetric SBS membranes prepared by the non-solvent induced phase inversion technique (NIPS) [4]. This technique allows tailoring the morphology of the prepared membrane and obtaining a resistant membrane with a thin active layer in a single step. The success of the preparation of asymmetric elastomeric membranes leads to an easier membrane production at lower cost with respect to the composite membrane production and to the possibility to tailor the membrane morphology. Different membrane structures were obtained by using different non-solvent/solvent pairs. The influence of several parameters on the membrane film formation, such as the composition of the polymer solution (concentration, type of solvent), composition of the coagulation bath, the exposure time before immersion in the coagulation bath, casting knife thickness, was investigated. Using small amount of polymer non- solvent (up to 5wt.%) into the solvent polymer solution asymmetric porous membranes were obtained (instantaneous demixing). Addition of solvent to the coagulation bath partially suppressed the porous formation and yielded membranes with a dense top-layer. In particular, the THF(solvent)/ethanol or

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ethanol/butanol (non solvent) combination allowed the formation of asymmetric membranes with a dense skin layer, suitable for pervaporation applications. A thicker dense layer was made increasing the polymer concentration (10wt.% to 25wt.%) in the casting solution. The surface and the cross-section of the prepared membranes were analysed using a Scanning Electron Microscopy (SEM). Gas and water permeability experiments have been also performed to evaluate the pore size diameter, porosity, and transport property of the active layer of the SBS asymmetric membranes. The asymmetric SBS flat membrane was successfully tested for VOCs removal from water by PV in a pilot setup, TCA was used as model VOCs species. Several process conditions, such as feed flow rate, temperature, vacuum pressure have been deeply investigated. From the experimental tests, the flux and separation factor obtained were higher than those achieved with commercial membranes. In particular, the best performance of the SBS asymmetric flat membrane showed a selectivity of about 4600 and a TCA flux of about 18 g/m2h at a temperature of 34 °C and 40 Torr [4].

References

1) W. Ji, S.K. Sikdar, S.T. Hwang, Modeling of multicomponent pervaporation for removal of volatile organic compounds from water, J. Membr. Sci. 93 (1994) 1.

2) I. Abou-Nemeh, S. Majumdar, A. Saraf, S.K. Sirkar, L.M. Vane, F.R. Alvarez, L. Hitchens, Demonstration of pilot-scale pervaporation systems for volatile organic compound removal from a surfactant enhanced aquifer remediation fluid II. Hollow fiber membrane modules, Environmental Progress,20, issue 1 (2001) 64-73.

3) B.K. Dutta, S.K. Sikdar, Separation of volatile organic compounds from aqueous solutions by pervaporation using S-B-S block copolymer membranes. Environ Sci Technol 33 (1999) 1709.

4) S.K. Sikdar, J.O. Burckle, B.K. Dutta, A. Figoli, E. Drioli, Method for Fabrication of Elastomeric Asymmetric Membranes from Hydrophobic Polymers,U.S. Patent 11/598,840; publish in May, 2008.

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Osmotically Driven Membrane Processes – 1 – Keynote

Tuesday July 15, 8:15 AM-9:00 AM, O’ahu/Waialua

Characterization of Solute Transport in Osmotically Driven Membrane Processes

N. Hancock (Speaker), Colorado School of Mines, Golden, CO, USA T. Cath, Colorado School of Mines, Golden, CO, USA, [email protected]

Osmotically-driven membrane processes are emerging water treatment technologies that have come under renewed interest and subjected to numerous investigations in recent years. These studies have mostly focused on novel applications of the forward osmosis process to augment and improve existing water treatment methods. Recent studies have focused on characterizing concentration polarization phenomena and its affect on the non-linearity of osmotically-driven processes and on the effect of forward osmosis membrane structure on process performance. However, osmotically-driven membrane processes have yet to undergo any exhaustive or focused studies to determine solute transport characteristics through the membrane. In the current study, we focus on characterization of the bi-directional diffusion of solutes in osmotically driven membrane processes.

Recent studies by Cath, et al. and Halloway, et al. have suggested utilizing forward osmosis as a pretreatment for reverse osmosis (RO) in order to enhance the treatment of various types of waste streams. These studies demonstrated that forward osmosis is an effective pretreatment for RO due to its ability to effectively treat severely impaired water with minimal membrane fouling and simple maintenance. Forward osmosis has a reduced fouling potential because of the membrane’s hydrophilicity (resulting in a lower fouling tendency from organic matter) and its operation with very low hydraulic pressure. Recent research, funded by the US Bureau of Reclamation and conducted by Martinetti, Childress, and Cath for Eastern Municipal Water District (EMWD) of Southern California demonstrated that forward osmosis can effectively augment existing brackish water desalination operations by enhancing water recovery.

In this process, forward osmosis is used to pretreat the concentrate from an existing brackish water desalination processes. The highly concentrated stream, rich in sparingly soluble solutes, contacts the active side of the forward osmosis membrane. Water diffuses through the membrane into a highly concentrated draw solution of controlled composition. The high selectivity of the forward osmosis membrane generates a moderately dilute draw solution. Yet, very slow diffusion of solutes also occurs in both directions during the process. Commonly, an RO process is used to produce a stream of purified water and a stream of re-concentrated draw solution to sustain the forward osmosis process. Using

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forward osmosis, the RO process is thus protected from scaling and fouling of any constituents present in the source of impaired water.

An important caveat of the forward osmosis process is that its membrane, like all synthetic semi-permeable membranes, is not perfectly selective. Sparingly soluble solutes, toxic metals, and other emerging contaminants of concern present in the feed solution, as well as the draw solution solutes, will inevitably diffuse across the forward osmosis membrane. The introduction of sparingly soluble solutes into the final RO stage may subsequently scale the RO membrane, while the diffusion of draw solution solutes against flow of water represents inefficiency in the system because lost solutes will have to be replenished. Despite the multi-barrier treatment obtained by such a system, there is still concern that toxic metals and other containments of interest will cross both the forward osmosis and RO membranes and contaminate the product stream.

In the current study, multiple tests were performed to elucidate the diffusion of solutes across two different cellulose triacetate forward osmosis membranes. These studies were performed with the aid of a novel supervisory control and data acquisition (SCADA) system developed by the authors. Using the SCADA system, the authors were able to conduct experiments at very steady conditions including constant temperatures, flux, and draw solution concentrations. These studies utilized feed solutions containing both single salts and synthetic brackish water to characterize specific and competitive solute diffusion through the forward osmosis membranes. Samples from these experiments were analyzed by ion chromatography (IC) and inductively coupled plasma (ICP) to determine solute transport across the membranes. Data collected from this analysis was used to determine the individual solute’s permeation tendency through the membrane.

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Osmotically Driven Membrane Processes – 2

Tuesday July 15, 9:30 AM-10:00 AM, O’ahu/Waialua

Forward-Osmosis Using Ethanol for Concentrate Minimization

J. Pellegrino (Speaker), University of Colorado, Boulder, CO, USA, [email protected] P. McCormick, Denver Water Department, Denver, CO, USA A. Mendoza, University of Colorado, Boulder, CO, USA

Ethanol has several compelling features for use as a "draw" agent for forward osmosis-based separation of water from aqueous electrolytes. Due to the high osmotic gradients available, it can be used in crystallization processes and therefore provide a method for overall concentrate minimization as part of an inland desalination strategy. We have previously presented the transport properties of several membrane materials (IEX and PVA) with respect to EtOH, H2O, and NaCl under diffusive transport conditions. Also, rudimentary process design analysis has been done to identify approaches for recovery of recycle draw solution and product water. In this work, we have performed batch crystallization experiments using model electrolyte mixtures and have measured the integrated transport properties for the several species in a flow system, and the crystallization kinetics and speciation results.

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Osmotically Driven Membrane Processes – 3

Tuesday July 15, 10:00 AM-10:30 AM, O’ahu/Waialua

A Novel Hybrid Forward Osmosis Process for Drinking Water Augmentation using Impaired Water and Saline Water Sources

C. Lundin (Speaker), Colorado School of Mines, Golden, CO, USA T. Cath, Colorado School of Mines, Golden, CO, USA, [email protected] J. Drewes, Colorado School of Mines, Golden, CO, USA

As water resources become more contaminated and over allocated, new sources of water must be developed. While many coastal areas are turning to reverse osmosis (RO) desalination, the energy requirements can be a large drawback. The large amounts of energy required for RO desalination is mainly due to the need to overcome the osmotic pressure of seawater. The high osmotic pressure of seawater limits the maximum recovery possible by RO systems. There are only a few ways of reducing the energy required, one of which is by reducing the osmotic pressure of the feed water, for example through dilution, thereby reducing the needed applied high pressure.

Concurrently in many coastal areas, treated wastewater effluent is being discharged to the ocean without providing any beneficial use; wasting a valuable resource. In some areas the effluent is put into non-potable reuse systems, and recently, some very progressive utilities have started using reclaimed water for indirect potable reuse. Indirect potable reuse can work well in some areas, but it requires a large natural water storage area (lakes or aquifer) and further treatment after extraction from the aquifer and before ultimate potable use. Thus, it might be more efficient to pursue direct potable reuse in certain circumstances. The two problems of energy demand and wasted reclaimed water could be synergistically solved if the impaired water stream could be safely used to dilute seawater before RO desalination.

In a newly patented approach, forward osmosis (FO) uses a saline stream (seawater or brackish water concentrate) to extract purified water from a source of impaired water. FO uses an osmotic pressure differential as the driving force; drawing water through a semi-permeable membrane and rejecting almost all dissolved contaminants in the process. Because FO uses only osmotic pressure as a driving force, its energy demand is very low. The diluted seawater is then processed through an RO desalination system which provides rejection of salts, as well as further rejection of dissolved contaminants that may have crossed the FO membrane from the impaired water source. Most importantly, because the saline water is diluted during FO, the energy required for subsequent RO desalination of the diluted saline water is reduced. Thus, the energy demand of

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the desalination plant is lessened and two significant barriers are in place to reject contaminants present in the impaired/reclaimed stream.

Recent progress in research has demonstrated that FO can be successfully implemented in a wide range of applications including wastewater treatment (e.g., landfill leachate, anaerobic digester sludge, and life support systems), desalination (e.g., seawater and brackish water), and pharmaceutical and food industries. Yet, very limited research has been conducted on the direct combination of desalination and impaired water reclamation; specifically with regards to trace organic rejection. Therefore, the main objectives of the currently AwwaRF-funded study are threefold: (1) investigate the performance (e.g., water flux; solute and solid rejections) and potential limitations of FO membranes for pretreatment of impaired/reclaimed water, (2) investigate the mechanisms behind the mass transport of organic contaminants across the membrane, and (3) develop recommendations and cost estimates for a FO/RO hybrid for the simultaneous treatment of impaired and saline water.

The process is tested on both bench and pilot scale. The bench scale setup is comprised of a custom built flat sheet FO membrane cell (0.07 m2), and a SEPA-CF flat sheet RO membrane cell for desalination of seawater. Following the bench-scale study, pilot-scale testing of the process is conducted in several wastewater reclamation facilities. Several water quality parameters are being measured including TOC (Shimatzu HTCO), anions (IC), and cations (ICP). Because measuring the rejection of specific micropollutants is difficult in highly saline solutions, an existing HPLC method is being modified using solid phase extraction.

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Osmotically Driven Membrane Processes – 4

Tuesday July 15, 10:30 AM-11:00 AM, O’ahu/Waialua

Osmotic Membrane Bioreactor and Pressure Retarded Osmotic Membrane Bioreactor for Wastewater Treatment and Water Desalination

A. Achilli (Speaker), University of Nevada, Reno, Reno, Nevada, USA, [email protected] T. Cath, Colorado School of Mines, Golden, CO, USA E. Marchand, University of Nevada, Reno, Reno, Nevada, USA A. Childress, University of Nevada, Reno, Reno, Nevada, USA

More stringent regulations and the ability to produce high quality effluent make membrane bioreactors (MBRs) an attractive process for domestic and industrial wastewater treatment. In a conventional MBR, microfiltration (MF) or ultrafiltration (UF) membranes are utilized and water is commonly filtered through the membranes using pressure. Suspended solids are completely rejected and substantial removal of organic carbon and nutrients can be achieved [1]. MBRs replace two pivotal stages of conventional activated sludge systems (biotreatment and clarification) with a single, integrated process. MBR effluent may be suitable for use as irrigation water, process water, or a source of potable water. For potable reuse (e.g., indirect reuse through aquifer recharge), advanced treatment such as reverse osmosis (RO), nanofiltration (NF), or chemical oxidation is necessary after the MBR [2]. The advantages of MBRs over conventional treatment have been thoroughly reviewed and include product consistency, reduced footprint, reduced sludge production due to a high biomass concentration in the bioreactor, and complete suspended solids removal from the effluent [3].

A novel MBR system that utilizes a submerged forward osmosis (FO) membrane in the bioreactor is investigated in the current study. In forward osmosis, water diffuses across a selectively permeable membrane from a solution of higher water chemical potential (lower osmotic pressure) to a solution of lower water chemical potential (higher osmotic pressure); in this application, water diffuses from the bioreactor into a controlled draw solution (DS). The FO membrane acts as a barrier to solute transport and provides high rejection of contaminants present in the wastewater stream. The diluted DS is reconcentrated using RO or distillation, and being reused in the FO process; the permeate is a high-quality product water. Thus, in most wastewater treatment applications, FO is not the ultimate process but rather a high-level pretreatment step before an ultimate reconcentration/desalination process.

Compared to the MF or UF process in a conventional MBR, the FO process in the osmotic membrane bioreactor (OMBR) offers the advantages of much higher rejection (semi-permeable membrane versus microporous membrane) without

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the need of applying pressure to withdraw the permeate. FO membranes are also likely to have lower fouling propensity compared to high pressure membranes [4].

Preliminary results from experiments conducted with a flat-sheet cellulose triacetate FO membrane and an NaCl solution as the DS demonstrated high sustainable water flux. Membrane fouling was minimal and controlled with osmotic backwashing. The FO membrane was found to reject 98% of organic carbon and 90% of ammonium; the OsMBR process was found to remove 99.8% of organic carbon and 97.7% of ammonium.

In certain situations, when a stream of concentrated brine from a desalination facility is available, an open-loop OsMBR could be used. In this configuration, the brine from a nearby desalination facility would be used as the DS and the diluted DS would be discharged to the sea. Sea discharge of the diluted DS would be environmentally favorable over direct discharge of the brine because the diluted DS concentration would be closer to that of seawater.

Further application of the OsMBR process is its possible utilization in osmotic power generation through pressure-retarded osmosis (PRO). PRO utilizes the FO principle as a basis for its operation. In PRO the DS is at elevated hydraulic pressure, lower than the osmotic pressure difference between the feed and the DS streams. The optimal hydraulic pressure at which the system should operate is a function of the osmotic pressures of the feed and DS streams and the membrane characteristics. The water that diffuses through the membrane is depressurized in a turbogenerator to recover beneficial energy. When OMBR is operated in PRO mode in order to recover energy, the process is referred to as the pressure retarded OMBR (ProMBR). Other novel combination of ProMBR will be introduced. Computer modeling performed with ideal systems demonstrated that ProMBR can potentially be a viable source of renewable energy.

References

[1] S. Judd, The MBR Book: Principles and Applications of Membrane Bioreactors in Water and Wastewater Treatment, Elsevier, 2006.

[2] P. Lawrence, S. Adham and L. Barro, Ensuring water re-use projects succeed - institutional and technical issues for treated wastewater re-use, Desalination, 152 (2002) 291-298.

[3] T. Stephenson, S. Judd, B. Jefferson and K. Brindle, Membrane bioreactors for wastewater treatment, IWA Publishing, 2000.

[4] A. Achilli, T.Y. Cath, E.A. Marchand and A.E. Childress, The forward osmosis membrane bioreactor: A low fouling alternative to MBR processes, Desalination, Accepted for publication.

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Osmotically Driven Membrane Processes – 5

Tuesday July 15, 11:00 AM-11:30 AM, O’ahu/Waialua

Osmotic Power - A New, Renewable Energy Source

S. Skilhagen (Speaker), Statkraft AS, Norway T. Holt, SINTEF, Scandinavia J. Dugstad, Statkraft AS, Norway, [email protected]

Osmotic power is a relatively new energy conversion concept even though osmosis has been known for several hundred years. Only 30-35 years ago, Prof. Sidney Loeb and his team at UCLA utilised the natural knowledge and proposed methods for the utilisation of osmotic pressure in power generation using membranes.

In the eighties and nineties, membrane technology was introduced successfully in many industrial applications and efficient semi-permeable membranes became available. In the late nineties the efficient transfer of mechanical energy be- tween fluids was also made possible. All the basic technology components necessary for efficient osmotic power production are therefore in principle available. New and more energy efficient membrane technology has been developed during the last few years.

During the last decades the increased global energy consumption, together with increased focus on the environment, demands for new soruces of environmentaly friendly energy. Osmotic power can represent one of the solutions for these challenges.

Statkraft, a North European electricity generator, is now planning to build an osmotic power plant prototype to further verify the osmotic power system.

Throughout the last 10 years, developments has led to believe that it is possible to develop the necessary membrane technology and the construction of the first osmotic power prototype will be completed in 2008. The commercial potential of osmotic power is identified and a wide R&D programme involving research centres and commercial developers on three continents are currently in progress.

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Osmotically Driven Membrane Processes – 6

Tuesday July 15, 11:30 AM-12:00 PM, O’ahu/Waialua

Influence of Membrane Support Layer Hydrophobicity on Water Flux in Osmotically Driven Membrane Processes

J. McCutcheon (Speaker), Stony Brook University, East Setauket, NY, USA, [email protected] M. Elimelech, Yale University, New Haven, CT, USA

Osmotically driven membrane processes, such as forward osmosis (FO) and pressure retarded osmosis (PRO), rely on the utilization of large osmotic pressure differentials across semi-permeable membranes to generate water flux. Previous investigations on these two processes have demonstrated how asymmetric membrane structural characteristics, primarily of the support layers, impact water flux performance. In this investigation, we demonstrate that support layer hydrophilicity, or wetting, plays a crucial role in water flux across asymmetric semi-permeable membranes. The results show that the polyester (PET) nonwoven and polysulfone supports typically present in thin-film composite (TFC) reverse osmosis (RO) membranes do not wet fully when exposed to water, thereby resulting in a marked decrease in water flux. A cellulosic RO membrane exhibited modestly higher water fluxes due to its more hydrophilic support layer. Removal of the PET layers from the cellulosic and TFC RO membranes resulted in an increased water flux for the cellulosic membrane and very little change in flux for the TFC membrane. Pretreatment with hydraulic pressure (RO mode), feed solution degassing, and use of surfactants were used to further elucidate the wetting mechanisms of the different support layers within each membrane. The importance of considering membrane support layer chemistry in further development of membranes tailored specifically for osmotically driven membrane processes is discussed.

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Osmotically Driven Membrane Processes – 7

Tuesday July 15, 12:00 PM-12:30 PM, O’ahu/Waialua

Developing Permeation Enhanced Nanofiltration Hollow Fiber Membranes Used in Forward Osmosis

K. Wang (Speaker), National University of Singapore, Singapore Q. Yang, National University of Singapore, Singapore T. Chung, National University of Singapore, Singapore, [email protected] J. Gin, Centre for Advanced Water Technology, Singapore

Osmosis is the natural diffusion of water that permeating through a semi-permeable membrane from a solution containing a low concentration of dissolved species to a solution having a higher concentration of dissolved species. Instead of employing hydraulic pressure as the driving force for separation in the reverse osmosis process, forward osmosis (FO) employs the osmotic pressure gradient to induce a net flow of water through the membrane into the draw solution (with high osmotic pressure), thus effectively separating the feed water from dissolved solutes. The main advantages of using FO in seawater desalination are that FO membrane has high rejection to a wide range of contaminants, and it may have a lower membrane fouling propensity than other pressure-driven membrane processes. The membranes used in FO process play a vital role on the FO performance of separation and productivity. Up to now, available commercial reverse osmosis membranes were employed in almost all FO processes. It is necessary to develop special FO membranes that can adapt for the forward osmosis application. Nanofiltration membranes may have potential applications in the realization of FO for their molecular-size pores on the selective layer to reject larger molecules, such as salts, sugars, starches, proteins, viruses, bacteria, and parasites. In this study, polybenzimidazole (PBI) hollow fiber membranes through dry-jet wet phase inversion were fabricated with different structures, for instances, wall thickness and porosity in order to investigate the effects of membrane morphology on the membrane performance during FO process. The support layer structure may have the important effect on the water transport due to the serious concentration polarization in the porous support layer. It is found that operating temperature also has an important influence on the permeation flux due to its effect on the solution viscosity.

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Asymmetric Polymeric Membrane Formation – 1 – Keynote

Tuesday July 15, 8:15 AM-9:00 AM, Wai’anae

Manipulation of Block Copolymer Nanostructure in Membranes Prepared by Solvent Evaporation and Non-Solvent Induced Phase Separation

W. Yave (Speaker), Institute of Polymer Research, GKSS Research Centre Geesthacht GmbH, Germany, [email protected] A. Boschetti-de-Fierro, Institute of Polymer Research, GKSS Research Centre Geesthacht GmbH, Germany V. Garamus, Institute of Materials Research, GKSS Research Centre Geesthacht GmbH, Germany K. Peinemann, Institute of Polymer Research, GKSS Research Centre Geesthacht GmbH, Germany V. Abetz, Institute of Polymer Research, GKSS Research Centre Geesthacht GmbH, Germany P. Simon, Institute of Polymer Research, GKSS Research Centre Geesthacht GmbH, Germany

Self-assembly of macromolecular components is considered as a key for the fabrication of periodically nanostructured materials [1]. Block copolymers, having two or more polymer blocks chemically bound to each other have received great attention due to their chemical functionality and physical properties [2, 3]. These copolymers have the ability to self-assemble into microdomains, and the manipulation of these patterns by a variety of physical and chemical methods has been the challenge of many scientists.

For membrane technology, block copolymers showing a perpendicular cylindrical structure at the surface combined with the simplicity of membrane preparation is of special interest [4, 5]. In our previous work we combined the self-assembly of a block copolymer with the well established non- solvent induced phase separation technique. An asymmetric membrane with an extremely well ordered top-layer was obtained [5]. After the first works it was noticed that not only the typical parameters as composition of copolymer solution, evaporation time and precipitation conditions are essential for the final membrane structure, but also the age of copolymer solution due to the structure formation in solution. Therefore, we prepared microphase separated films by evaporation of block copolymer solutions, after storing them for different times. Small angle neutron scattering experiments carried out on these solutions indicated structural changes as a function of time. The time dependence on the final nanostructure of the cast films will be discussed.

The process described above was then combined with the phase inversion process, and nanostructured asymmetric membranes could be produced. By using block copolymers of different compositions and different casting conditions, the quality of the self-assembly in the top layer could be controlled.

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References: [1] Stupp, S. I.; Lebonheur, V. ; Walker, K.; Li, L.S.; Higgins, K.E.; Kesser, M.; Amstutz, A. Science 1997, 276, 384. [2] Bates, F. S. Science 1991, 251, 898. [3] Abetz, V. ed. Block Copolymer I and II Vol. 189 and 190, Springer Publisher Heidelberg (2005). [4] Kim, S.H.; Misner, M.J.; Xu, T.; Kimura, M.; Russell, T.P. Advanced Materials 2004, 16, 226. [5] Peinemann, K.-V.; Abetz, V.; Simon, P.F.W. Nature Materials 2007, 6, 992 .

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Asymmetric Polymeric Membrane Formation – 2

Tuesday July 15, 9:30 AM-10:00 AM, Wai’anae

Synthesis and Characterization of Nanoporous Polycaprolactone Membranes for Controlled Drug Release

C. Yen (Speaker), The Ohio State University, Columbus, OH, USA H. He, Nanoscale Science and Engineering Center for Affordable Nanoengineering of, Columbus, OH, USA L. Lee, The Ohio State University, Columbus, OH, USA W. Ho, The Ohio State University, Columbus, OH, USA

Polycaprolactone (PCL) has recently drawn a lot of attention in the biomedical applications. PCL, a semicrystalline polymer, has several advantages including low cost, biocompatiblitiy, and biodegradability. Moreover, PCL is a U.S. Food and Drug Administration approved material for implantable devices, such as suture. Thus, PCL is a superior material to fabricate an affordable and implantable drug delivery device.

The porous membranes play an important role in a variety of drug delivery systems. Several factors, including porosity, turtuosity, and pore size, have critical effects on controlling the rate of drug diffusion through the membranes. Currently, porous PCL membranes can be prepared by solvent-cast-leaching method, bi- axial stretching, thermally-induced phase separation, and nonsolvent-induced phase separation. However, state-of-the-art, porous PCL membranes which are prepared via above methods have pore size still on a micron scale that is too large. The mechanism governing diffusion phenomena could be free diffusion, leading to an undesirable burst effect. Therefore, micron-size porous membranes might not be a proper means to achieve the desirable zero-order drug release rate. It appears that nanoporous PCL membranes could be an ideal system to achieve the desirable release rate for implantable drug delivery devices.

In this study, nanoporous PCL membranes have been prepared successfully via the combination of thermally and nonsolvent induced phase separations. In the membrane formation, the effects arisen from the thermally-induced phase separation on the membrane formation have been investigated. In the membrane preparation, the cast-film on a glass plate was immersed into a coagulation (water) bath at a different constant temperature. When water bath temperature was 5° C, the pore size at membrane top side was approximately 50 nm, and the porosity was about 73%. However, while water temperature increased, the pore size would also increase but the porosity would decrease. As coagulation bath temperature increased to 35°C, the pore size at top side of the membrane would be about 1 µm, and the porosity was about 56%. Lower coagulation

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temperatures might bring about the enlarged phase-separation and crystallization areas. Based on the 3-phase diagram, the composition path may cross the bimodal line and move into the crystallization area. Therefore, crystallization could suppress pore coalescence to ensure a well-connected pore structure. Moreover, the use of nonsolvent, water, in the wet process of the nonsolvent induced phase separation would produce nanopores at the top side of membranes. Also, the influence of coagulation composition on the membrane structure will be discussed. Various coagulation bath compositions would bring about a different pore size on the top side of the membrane. By understanding the fundamental parameters related to the formation of membrane structure, nanoporous membrane-based implantable drug delivery devices with the preprogrammed drug release rate would be developed.

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Asymmetric Polymeric Membrane Formation – 3 Tuesday July 15, 10:00 AM-10:30 AM, Wai’anae

Catalytic PVDF Microcapsules for Application in Fine Chemistry

M. Buonomenna, ITM-CNR c/o UNiversity of Calabria, Italy, [email protected] A. Figoli (Speaker), ITM-CNR c/o UNICAL, Italy I. Spezzano, ITM-CNR, Italy E. Drioli, ITM-CNR, Italy

Microcapsules have found numerous applications in various fields, such as pharmaceutical, chemical, textile, biomedical, environmental, petroleum and pesticide industries, and so on [1,2]. In particular, in the field of catalysis, when encapsulating a catalyst or enzyme, a potentially high interfacial specific area is created and the recovery of the catalyst is facilitated. The selective sorption through the membrane can further increase catalytic performances. In this study, we report on the preparation, characterization and use of new catalytic polymeric microcapsules for application in fine chemistry. The catalyst, ammonium molybdate tetrahydrate, was entrapped inside PVDF polymeric microcapsules during their preparation. Common techniques for fabricating hollow microcapsules with dense or porous membranes include interfacial polymerization, in situ polymerization [3-5], and phase inversion [6-8]. In particular, using phase inversion method, microcapsule membranes based on cellulose acetate (CA), ethylcellulose (EC) [9,10], polyethersulphone (PES) [11] and PEEKWC [12] characterized by pore microstructure both straight and packed throughout the whole membrane thickness were prepared. These morphological properties were obtained by using additives in the polymeric solutions as LiCl, PVP and PEG400 or acetone, alcohol, glycerin, or TEC in various ratio, that are responsible for an increase of demixing rate and for a more porous structure. In this communication, we will report on new PVDF catalytic microcapsules prepared by means of phase inversion induced by non-solvent without use of additives in the polymeric solutions to prevent catalyst deactivation. The developed catalytic microcapsules are featured with a reservoir-type porous microcapsule membrane structure and with numerous straight microchannels across the membrane. The hollow structure provided large space for immobilizing the catalyst inside the proposed microcapsule, and the straight microchannel structure across the membrane significantly reduced the mass transfer resistance [13]. The chemical-physical analysis of the new PVDF catalytic microcapsules was carried out by means of SEM, EDX, IR, DSC and XRD techniques. Catalytic activity of the PVDF catalytic microcapsules has been evaluated in the oxidation of aromatic alcohols to corresponding aldehydes in solvent free conditions. The polymeric microcapsules “keep in contact” the two phases: the organic phase, containing the substrate and the product, and the aqueous phase with the oxidant, H2O2. In this way, every microcapsule works as a catalytic membrane reactor with both the catalytic and contactor functions.

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References

[1] S. Benita, Microencapsulation: Methods and Industrial Applications, Marcel Dekker, New York, 1996.

[2] A. Kondo, Microcapsule Processing and Technology, Marcel Dekker, New York, 1979.

[3] L.-Y. Chu, S.-H. Park, T. Yamaguchi, S. Nakao, Langmuir 18 (2002) 1856.

[4] Suryanarayana, P.S. Sai Prasad, Catal. Commun. 7 (2006) 245.

[5] L. Yuan, G.Z. Liang, J.Q. Xie, L. Li, J. Guo, J. Mater. Sci 42 (2007) 4390.

[6] C.Y. Wang, H.O. Ho, L.H. Lin, Y.K. Lin, M.T. Sheu, Int. J. Pharm. 297 (2005) 89.

[7] A.G. Thombrea, J.R. Cardinal, A.R. DeNoto, S.M. Herbig, K.L. Smith, J. Control. Release 57 (1999) 55.

[8] G.J. Wang, L.Y. Chu, M.Y. Zhou, W.M. Chen, J. Membr. Sci. 284 (2006) 301.

[9] C.Y. Wang, H.O. Ho, L.H. Lin, Y.K. Lin, M.T. Sheu, Int. J. Pharm. 297 (2005) 89.

[10] A.G. Thombrea, J.R. Cardinal, A.R. DeNoto, S.M. Herbig, K.L. Smith, J. Control. Release 57 (1999) 55.

[11] G.J. Wang, L.Y. Chu, M.Y. Zhou, W.M. Chen, J. Membr. Sci. 284 (2006) 301.

[12] A.Figoli, G. De Luca, E. Longavita, E.Drioli, Sep. Sci. Technol.42 (2007) 2809.

[13] M.G. Buonomenna, A.Figoli, I. Spezzano, M. Davoli, E.Drioli, Applied Catalysis B: Environmental 80 (2008) 185.

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Asymmetric Polymeric Membrane Formation – 4

Tuesday July 15, 10:30 AM-11:00 AM, Wai’anae

The Impact of Solvent on the Microstructure of Integrally Skinned Polyimide Nanofiltration Membranes before and after casting

D. Patterson (Speaker), Department of Chemical and Materials Engineering, The University of Auckland, Auckland, New Zealand, [email protected] S. Costello, Department of Chemical and Materials Engineering, The University of Auckland, Auckland, New, Zealand A. Havill, Department of Chemical and Materials Engineering, The University of Auckland, Auckland, New, Zealand Y. See-Toh, Department of Chemical Engineering and Chemical Technology, Imperial College, London, UK A. Livingston, Department of Chemical Engineering and Chemical Technology, Imperial College, London, UK A. Turner, School of Biological Sciences, The University of Auckland, Auckland, New Zealand

Due to their excellent resistance to a range of solvents, integrally skinned polyimide membranes have been used as nanofiltration membranes to achieve selective separations in a range of industrial and lab-scale chemical operations. These include: homogeneous catalyst recycle, petrochemical dewaxing, solvent exchange and chiral resolutions. However, despite the widening scope of use of these membranes, there is still little understanding of how different casting and filtration solvents affect their microstructure and how this impacts on membrane separation performance. Part of this question arises because the microstructure of nanofiltration membranes are typically characterised using dry membranes. However, during a filtration, the structure of the membrane changes when in contact with the solvent to be used, especially due to swelling. Therefore, although imaging a membrane outside of a solvent (dry) may give an indication of the initial microstructure prior to filtration, in order to understand how the microstructure affects the transport mechanism and thus membrane separation performance when it is being used, the membrane must be imaged when in solvent (wet).

As a first step towards answering the above question, integrally skinned nanofiltration membranes were fabricated by phase inversion using Lenzing P84 polyimide. A range of P84 membranes were fabricated, varying three formation parameters: doping solution solvents, evaporation time and post heat treatment temperature. The doping solvents used were n-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylformamide, 1,4-dioxane and acetone. The evaporation times varied were 10 seconds, 30 seconds and 60 seconds. The heat treatment temperatures were 100°C, 150°C and 200°C. The effect these parameters had on the membrane microstructure, filtration performance and mechanical strength were then characterised. The microstructure of these membranes, dry and in

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solvent, were investigated (where appropriate) by scanning electron microscope (SEM), transmission electron microscope (TEM) and environmental scanning electron microscope (ESEM). The membrane performance was determined by measuring the flux from a dead-end filtration cell using ethanol as the filtration solvent. The mechanical strength was determined from a tensile test.

SEM and TEM imaging of dry membranes revealed that this type of polyimide membrane has three microstructurally distinct polyimide layers, not the two indicated in prior literature. The top skin layer consists of closely packed polymer nodules. The middle layer is a microstructure transition region where the microstructure changes with the densely packed polymer nodules slowly becoming more interconnected and less densely packed further from the membrane surface. The bottom layer is a uniformly porous support layer consisting of an interconnected polyimide network. Furthermore, TEM images reveal nano-sized pores in the polyimide structure, which indicate that the transport mechanism for these membranes is probably neither only solution-diffusion nor only pore-flow.

The different casting solvents used changed the microstructural characteristics of these three layers. In particular, it was found that acetone had the effect of increasing the density of the membrane skin layer and increasing the thickness of the membrane skin layer by 50nm. This was attributed to the fact that acetone is a more volatile solvent than the other solvents used. Increasing the evaporation time from 10 seconds to 30 seconds and 60 seconds increased the density of the skin layer also, leading to smaller nano-sized pores in the membrane skin layer. An increase in heat treatment temperature also increased the skin layer density. This could be attributed to the heat treatment allowing the polymer chains to align in a more thermodynamically stable arrangement.

ESEM imaging showed that when saturated in ethanol, the microstructure of the membranes changes: it is wispy and thus quite different to the more solid polymer nodules and interconnected polymer network observed in the dry membranes. Thus, transport and separation mechanisms based on the structure of the dry membranes may not be completely accurate. Membranes cast with acetone as a solvent swelled the most in ethanol. The 200°C heat treated membrane did not swell excessively, perhaps indicating that the thermodynamically stable arrangement of polymer chains impeded solvent entry.

Overall, these results indicate that the current theory used to describe polyimide membrane mass transfer and separation performance must be rethought. Furthermore, as currently there is no definitive definition for the thickness of the skin layer of these membranes, based on the dry morphology observed here, it is proposed that the dry skin layer thickness be defined as the length perpendicular from the top surface of the membrane to the point where these pores become interconnected.

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Asymmetric Polymeric Membrane Formation – 5

Tuesday July 15, 11:00 AM-11:30 AM, Wai’anae

Nanofiltration Membranes for Polar Aprotic Solvents

F. Lim (Speaker), Membrane Extraction Technology Ltd., Fulham, London, UK, [email protected] Y. See-Toh, Imperial College London, London, UK I. Sereewatthanawut, Membrane Extraction Technology Ltd., Fulham, London, UK A. Boam, Membrane Extraction Technology Ltd., Fulham, London, UK A. Livingston, Imperial College of London, Membrane Extraction Technology Ltd., Fulham, London, UK

This paper will present new work undertaken as a collaboration between Imperial College and Membrane Extraction Technology Ltd. This has resulted in the development of the first reported polymeric nanofiltration membranes which are stable in aggressive solvents such as methylene chloride (DCM), tetrahydrofuran (THF), dimethyl formamide (DMF) and n-methyl pyrrolidone (NMP) [1]. These membranes have been further developed into spiral wound elements, which are also stable in these aggressive liquids.

The recent advent of commercial Organic Solvent Nanofiltration (OSN) membranes has opened up a wide range of potential applications. OSN allows economic and efficient separation of molecules in the range 200 - 1000 g mol-1 and can be employed in many sectors including the petrochemical, food and beverage, biotechnology and pharmaceutical industries. The majority of OSN membranes are either composites comprising a polydimethylsiloxane (PDMS) separating layer on a polyacrylonitrile (PAN) support, or integrally skinned asymmetric membranes made of polyimides (PI). Although PAN shows good chemical resistance in many solvents, the PDMS separating layer swells appreciably in many solvents resulting in limited solvent stability. Commercial PI OSN membranes have been shown to give good performances in several organic solvents (e.g. toluene, methanol, ethyl acetate etc. [2]) but are however unstable in some amines and have generally poor stability and performance in polar aprotic solvents such as DCM, THF, DMF and NMP, in which most of these membranes are soluble. Inorganic membranes have been developed which offer good stability in organic solvents, but they are often more expensive and difficult to handle. To date, there are few reports of OSN in aggressive solvents such as THF, DMF and NMP.

Crosslinking of polymeric membranes has been shown to increase their chemical and thermal stability [3]. However, this is often at the expense of a decrease in permeability. Several crosslinking strategies for polyimide (PI) have been proposed including the use of radical initiated (thermally or via the use of UV) and chemical crosslinks [4]. Post casting modification of polymer films provides

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ease of manipulation as this allows the desired morphology of the membranes to be attained via phase inversion followed by further crosslinking on the pre-formed membrane to maintain this morphology in aggressive conditions. In OSN, where membrane stability of the under-layer is as critical as the separating layer, effective and uniform crosslinking of the whole membrane must be achieved. This suggests the use of radical initiated methods which would have difficulty of achieving crosslinking throughout the whole membrane. Instead, we chose chemical crosslinking as the preferred method to achieve uniform crosslinking throughout the membranes. Several chemical crosslinking strategies for use in PI membranes have been proposed and include the use of di/poly-amines in a ring opening reaction [4] and the inclusion of condensable crosslinking sites during polymer preparation.

A range of solvent stable organic solvent nanofiltration membranes were prepared through the chemical crosslinking of preformed integrally skinned PI membranes using aliphatic diamines. The resultant membranes had a spongy structure and were stable in many organic solvents including toluene, methanol, acetone, DCM, THF, DMF and NMP. The further development of the membrane into spiral wound elements was undertaken, involving scaling up the membrane production process and then developing spiral wound elements that are stable in aggressive solvents. Extended periods of both flat-sheet and spiral-wound element testing in DMF and THF for e120 h showed that the membranes and elements have a stable flux and good separation performance, with DMF permeability in the range of 1-8 L m-2 h-1 bar-1 and Molecular Weight Cut-Off (MWCO) between 250-1000 g mol-1. However possible re- imidization and loss of crosslinking at elevated temperatures limits their range of application to temperatures <100 degree Celsius. Their ease of preparation and reliability makes the membranes easily scalable and also widens up future possibilities for further applications in a range of organic solvent environments. This presentation will describe these developments.

References:

[1] Y.H. See-Toh, F.W. Lim and A.G. Livingston, J.Mem.Sci, 301 (2007) 3.

[2] P. Silva, S. Han and A.G. Livingston, J.Mem.Sci, 262 (2005) 49.

[3] Hayes R.A., US Patent 4717393, 1988.

[4] Y. Liu, R. Wang and T.S. Chung J.Mem.Sci, 189 (2001) 231.

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Asymmetric Polymeric Membrane Formation – 6

Tuesday July 15, 11:30 AM-12:00 PM, Wai’anae

Phase Separation Microfabrication

M. Bikel (Speaker), Membrane Technology Group - University of Twente, The Netherlands R. Lammertink, Membrane Technology Group - University of Twente, The Netherlands, [email protected] M. Wessling, Membrane Technology Group - University of Twente, The Netherlands

Phase Separation Micro Fabrication (PSuF) entails the phase separation of polymer solutions that are cast onto structured supports which serve as molds. In this way, microstructured membranes can be obtained without the use of cleanroom technology. The replication of the pattern on the mold makes these membranes asymmetric from a structural point of view, as one side is flat and the other one is structured. The structural asymmetry can be obtained independently from the morphological one. Here, we focus on the effects of this pattern and other variables on the final structural and morphological asymmetry of membranes obtained from a PES/PVP/NMP/water system.

Many kinds of features can be replicated down to the micron range, even with high aspect ratios. These features can be indentations into the membrane surface as well as protrusions of polymeric material emerging from the patterned surface. With small adaptations, this process is extendable to the structuring of hollow fibers, whether be it for structuring the outside of the fiber, its lumen or both.

By means of introducing different features on the molds, the phase separation mechanism could be studied and changed. The presence of a small amount of features allowed us to study the process by observing the effect of the final morphology on the replication of the features. Several types of distortion were observed when the polymeric matrix shrunk away from the mold walls. Generally, indentations on the membranes were larger than the features and polymeric protrusions, smaller.

An increase in the number or total area of the features decreased the deformation of the replicas to a minimum. In this case, the pattern has an effect on the morphology. This has to do with the lack of access to the space between the mold and the polymer solution, implying that less non-solvent comes directly in contact with the features. Instead, the whole phase separation takes place through the diffusion of the non-solvent through the polymer solution, yielding membranes with a different morphology. To further analyze this, we used a third mold with deeper features. In this case, local thinning of the film above the features was observed. This can be related to pulling forces during shrinkage.

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Horizontal shrinkage does not have an effect as high as that of vertical shrinkage. This is due to the different interaction of the layers in each direction, which leads to different levels of accumulation of these effects. As a rule of thumb, the relative vertical shrinkage is uniform, whereas the lateral one is not. This happens because when shrinking, each layer is impeded by the layers directly above it which have already solidified.

Coagulation baths with increasing NMP to water ratios were tried, finding minimum values for macrovoid suppression. Their effect on the solidification of the membrane was also assessed. The inclusion of a vapor bath before immersion precipitation was studied for creating a skin that slowed down the exchange of solvent and non-solvent. For systems where a critical casting thickness can be found, it has been seen that macrovoids tend to accumulate inside the features, where the membrane is thicker.

Tunability of the porosity of the membrane is an interesting feature since the inner structure of the membrane is also of high importance for the different applications. Therefore, a methodical study of the PES/PVP/NMP/water system was carried out. Variations in the compositions of both the casting solution and the coagulation bath were tested for influence on the thickness, extent of shrinkage and porosity of the final membrane. This has shown that the final morphology of the membrane can be modified, including the appearance of the skin layer.

The study of PSuF has clarified several aspects of the phase separation process. The tests we have performed have provided us with tools to foresee and work around potential challenges when patterning membranes for future applications.

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Asymmetric Polymeric Membrane Formation – 7

Tuesday July 15, 12:00 PM-12:30 PM, Wai’anae

In-Line and In-Situ Determination of Non-Solvent, Solvent and Polymer Composition within a Film-Forming System prior to Phase Separation during VIPS

W. Werapun, Université Montpellier, Montpellier, France D. Bouyer (Speaker), Université Montpellier, Montpellier, France, [email protected] C. Pochat-Bohatier, Université Montpellier, Montpellier, France A. Deratani, CNRS, Montpellier, France C. Dupuy, Université Montpellier, Montpellier, France

Two processes can be used to promote the transfer of the non-solvent into the polymer solution: immersion wet casting into a coagulation bath (Non-Solvent Induced Phase Separation), and exposure to a non-solvent vapor atmosphere, usually humid air (VIPS). The main interest for using the VIPS process consists of reduction in mass transfer kinetics. The obtained membranes are characterized by a more homogeneous morphology. Furthermore, there has been a growing interest in VIPS process because when it is applied prior to the immersion in a coagulation bath it could prevent the formation of the macrovoids generally obtained by a direct immersion. VIPS has been studied mainly during the last decade, through experimental works and also modeling approaches. Recently, different mathematical descriptions were developed to describe the mass transfer kinetics related to VIPS. Nevertheless, the experimental validation of such models appears quite difficult, and the models have not been validated by experimental results, but with global gravimetric measurements. The main objective of this work consists in using the Near Infra-Red Spectroscopy (NIRS) for following in-line, i.e. during the VIPS process, and in-situ, i.e. directly in the polymer solution, the concentration evolution of the three components. The polymer solution was placed into a rectangular cuvette and then exposed to non-solvent vapor. The solution composition was followed at different depths using NIRS during the VIPS under monitored RH, temperature and hydrodynamics conditions.

The experiments were conducted using different polymer/solvent systems and the water was the non-solvent in each case. The polymers used in this study were PEI (poly(bisphenol A-co-4- nitrophtalic anhydride-co-1,3-phenylenediamine, Sigma Aldrich) and Poly(EtherSulfone) (PES) (Ultrason E6020P, BASF). Each polymer was dissolved in two different solvents: dimethylacetamide (DMAc) and (NMP) for PEI and dimethylformamide (DMF) and NMP for PES. The composition of each polymer/solvent systems was initially 12/88 in mass fraction (wt-%).

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Absorption of water was determined both by gravimetric and by NIRS measurements. Experiments were carried out in a static mode, i.e. without any air circulation. The open cell was placed in a closed vessel at 40°C with an atmosphere with fixed RH controlled by a saturated salt solution (NaCl for 75% RH).

Fourier transform NIRS in a transmission mode was used to measure the transfer of water within an elementary volume of polymer solution. NIR spectra were recorded each 30 min using a Perkin Elmer Spectrum One NTS equipped with a tungsten- halogen lamp with a quartz envelope and a deuterated triglycine sulfate (DTGS) detector. The instrument was controlled via the software Spectrum v3.02 from Perkin Elmer, which permits acquisition and processing of spectra. Four scans were averaged at a 4 cm-1 resolution in the range of 2600-10000 cm-1. The size of the laser spot was set equal to 2.5 mm diameter, and the analyses were performed at 7 mm under the air/solution interface. Gravimetric measurements were used as a reference method to evaluate the NIR method.

The NIR measurements performed on different systems during VIPS exhibit the following points:

The composition of the solution, in terms of polymer, solvent and non-solvent local concentration has been successfully followed in- line and in-situ. Before the phase separation takes place, whatever the system the evolution curves representing the local concentration of water gradually increase whereas the solvent concentration decreases and the concentration of the polymer remains almost constant.

The concentration of the three components can be followed not only before but also after the phase separation has occurred at the top surface of the polymer solution, since the points of measurement are placed under the top surface. This aspect is of special interest for studying the mass transport phenomena at different stages of the membrane formation. Nevertheless, as soon as the solution phase separates at the point of measurement, the NIR analysis is no more possible.

The time needed for reaching the phase separation at the top surface of the polymer solution can be easily determined from the experimental curves. Indeed, demixing leads to a drastic change in the mass transport phenomena due to the formation of a polymer precipitated surface layer. The penetration rate of non-solvent is also reduced resulting in a change of slope in the absorption curves, the critical point indicating complete surface phase separation.

Using three points of measurements within the polymer solution, concentration profiles can be plotted during time. These results could help validating numerical mass transfer model using the VIPS process. In addition, the method allows the apparent diffusion coefficients to be determined.

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Oral Presentation Abstracts

Afternoon Session

Tuesday, July 15, 2008

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Gas Separation II – 1 – Keynote

Tuesday July 15, 2:15 PM-3:00 PM, Kaua’i

Highly Gas-Permeable Substituted Polyacetylenes: Recent Advances

T. Masuda (Speaker), Kyoto University, Kyoto, Japan - [email protected]

Polyacetylenes having various substituents (substituted polyacetylenes) can be synthesized by use of metathesis catalysts (W, Mo, Ta, and Nb) [1-3]. Among those polymers, poly[1-(trimethylsilyl)-1-propyne] [poly(TMSP)] exhibits higher gas permeability than any known synthetic polymers. Its oxygen permeability coefficient (Po2) varies depending on preparation and measuring conditions, but its typical value is ca. 10,000 barrers at 25 °C [4,5]. In-depth reviews of poly(TMSP) are available [1,3,5].

Apart from poly(TMSP), pretty many substituted polyacetylenes are now known to be more gas-permeable than poly(dimethylsiloxane), the most permeable commercial membrane material. One of them is poly[1-phenyl-2-(p-trimethylsilylphenyl)acetylene] [poly(p-Me3Si-DPA)] [6], whose oxygen permeability is around 1,500 barrers.

More, recently, the polymerization of 1-(1,1,3,3-tetramethylindan-5-yl)-2-phenylacetylene (1), 1-(1,1,2,2,3,3-hexamethylindan-5-yl)-2-phenylacetylene (2), and 1-(1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene-6-yl)-2-phenylacetylene (3) was carried out with TaCl5-n-Bu4Sn catalyst [7]. All the monomers gave high molecular weight polymers (Mw ~1,000,000) in good yields. The formed polymers were soluble in common solvents including cyclohexane, toluene, CHCl3, and THF. Free-standing membranes of poly(1) -poly(3) were fabricated by casting toluene solution. According to thermogravimetric analysis (TGA) measured in air, these polymers exhibited excellent thermal stability (T0 ~400 °C). The membranes of these polymers showed extremely high gas permeability (Po2 4,000-14,000 barrers); especially the Po2 value of poly(1) reached 14,000 barrers. The PO2/PN2 ratios were in a range of 1.24-1.44.

Derivatives 4-6 of monomer 1 that have a para-halo-substituent [1-(1,1,3,3-tetramethylindan-5-yl)-2-(4-X-phenyl)acetylenes; 1: X = H, 4: X = F, 5: X = Cl, 6: X = Br] were polymerized with TaCl5-n-Bu4Sn catalyst to give high molecular weight polymers (Mw ~1,000,0000) in moderate yields [8]. Poly(4) -poly(6) were soluble in common organic solvents, and gave free-standing membranes by solution casting. These polymers possessed excellent thermal stability according to TGA (T0 ~410 °C). The membranes of these polymers displayed high gas permeability (Po2 5,000-17,900 barrers). In particular, the oxygen permeability of

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poly(4) reached up to 17,900 barrers, which is even larger than that of the so far most permeable PTMSP.

Poly(diphenylacetylene) [poly(DPA)] membrane was successfully prepared by desilylation of poly(p-Me3Si-DPA) membrane catalyzed by trifluoroacetic acid. This is quite interesting because poly(DPA) membrane cannot be fabricated directly because of the insolubility of the polymer [9,10]. The membrane of poly(DPA) is fairly permeable to oxygen (Po2 = ca. 1,000 barrers) in spite of the absence of any spherical substituents.

It is impossible to directly obtain substituted polyacetylenes having polar groups such as hydroxy groups because of catalyst deactivation during polymerization, but this has been achieved by an indirect method. Namely, poly[1-p-(t-butyldimethylsiloxyphenyl)-2-phenylacetylene] was at first synthesized, and then its membrane was treated with CF3COOH/H2O to provide poly[1-(p-hydroxyphenyl)-2-phenylacetylene] membrane. This oxygen-containing polymer also shows fairly high oxygen permeability (250 barrers), and more interestingly it shows large CO2 permselectivity (PCO2 110 barrers; PCO2/PN2 46) [11].

1. T. Masuda and K. Nagai, in ‘Materials Science of Membranes for Gas and Vapor Separation’, Yu. Yampolskii, I. Pinnau, B. D. Freeman, Eds., Wiley, Chichester, Chapter 8 (2006).

2. T. Masuda, J. Polym. Sci., Part A: Polym. Chem., 45, 165 (2007).

3. K. Nagai, Y.-M. Lee, and T. Masuda, in ‘Macromolecular Engineering: Precise Synthesis, Materials Properties, Applications’, K. Matyjaszewski, Y. Gnanou, and L. Leibler, Eds., Wiley-VCH, Weinheim, Vol. 4, Chapter 12 (2007).

4. T. Masuda, E. Isobe, T. Higashimura, and K. Takada, J. Am. Chem. Soc., 105, 7473 (1983).

5. K. Nagai, T. Masuda, T. Nakagawa, B. D. Freeman, and I. Pinnau, Prog. Polym. Sci., 26, 721 (2001).

6. K. Tsuchihara, T. Masuda, and T. Higashimura, J. Am. Chem. Soc., 113, 8548 (1991).

7. Y. Hu, M. Shiotsuki, F. Sanda, and T. Masuda, Chem. Commun., 4269 (2007).

8. Y. Hu, M. Shiotsuki, F. Sanda, B. D. Freeman, and T. Masuda, J. Am. Chem. Soc., submitted.

9. M. Teraguchi and T. Masuda, Macromolecules, 35, 1149 (2002).

10. T. Sakaguchi, K. Yumoto, Y. Shida, M. Shiotsuki, F. Sanda, and T. Masuda, J. Polym. Sci, Part A Polym. Chem., 44, 5028 (2006).

11. Y. Shida, T. Sakaguchi, M. Shiotsuki, and T. Masuda, Macromolecules, 38, 4096 (2005).

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Gas Separation II – 2

Tuesday July 15, 3:00 PM-3:30 PM, Kaua’i

Modeling Molecular-Scale Gas Separation

A. Thornton (Speaker), CSIRO, Clayton, Australia - [email protected] T. Hilder, University of Wollongong, Wollongong, Australia - [email protected] A. Hill, CSIRO, Clayton, Australia - [email protected] J. Hill, University of Wollongong, Wollongong, Australia- [email protected]

The ability to separate gas mixtures is a vital skill in a world that emits excess carbon dioxide into the atmosphere, needs purified water, wants artificial kidneys, requires hydrogen for energy alternatives and demands many more improvements and developments. Gas separation membranes are composed of nano- sized pores which may be designed to separate a gas mixture. In this paper we employ mathematical modeling using the Lennard-Jones interactions between the gas molecule and the pore wall to determine an ideal pore radius in terms of efficiently separating molecules. The method adopted is closely related to carbon nanotube forest-based membranes and can also be used to explain the performance of polymer membranes such as thermally rearranged (TR), poly (trimethylsilylpropyne) (PTMSP) and conventional dense polymers. All the nanotubes in a carbon nanotube forest have the same radius enabling a more deterministic separation outcome. While polymers on the other hand have a distribution of pore sizes and therefore have an inbuilt capacity to perform various separations. This investigation reveals the acceptance radius and the radius of pores which provide a maximum suction energy for gases He, H2, CO2, O2, N2 and CH4. By assuming there are three different separation mechanisms namely blockage, suction and freeway, we may qualitatively explain the separation outcomes of TR, PTMSP and conventional polymer membranes.

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Gas Separation II – 3

Tuesday July 15, 3:30 PM-4:00 PM, Kaua’i

Physical Aging in Thin Glassy Polymer Films: A Variable Energy Positron Annihilation Lifetime Spectroscopy Study

B. Rowe (Speaker), The University of Texas at Austin, Austin, Texas, USA - [email protected] A. Hill, CSIRO, Clayton, Australia - [email protected] S. Pas, CSIRO, Clayton, Australia - [email protected] R. Suzuki, AIST, Ibaraki, Japan - [email protected] B. Freeman, The University of Texas at Austin, Austin, Texas, USA - [email protected] D. Paul, The University of Texas at Austin, Austin, Texas, USA - [email protected]

Most gas separation membranes are formed from glassy polymers because of their exceptional permeability-selectivity properties. However, glassy polymers are non-equilibrium materials that will spontaneously, but usually slowly, change over time towards an equilibrium state by a process known as physical aging. The physical aging rate becomes orders of magnitude more rapid if the thickness of the film is decreased below about one micron.1 This phenomenon is an intrinsically fascinating scientific issue, and understanding physical aging has broad impacts in several technologies including the gas separation industry.

New insight regarding the mechanisms behind physical aging can be gained by studying the free volume profile in polymer films during the aging process. Positron annihilation lifetime spectroscopy (PALS) is a powerful tool capable of determining the size and concentration of free volume sites in polymer systems by measuring the lifetime of injected positrons.2 The coupling of PALS with a variable mono-energetic positron beam source has resulted in a relatively new technique which allows the energy of the incident positron beam, and, therefore, penetration depth, to be controlled.3 This research will help provide a better fundamental scientific understanding of why aging rate depends on thickness, particularly at the molecular level.

The effect of physical aging on free volume and its distribution across the thickness of thin (l ~ 450 nm) polysulfone (PSF) films was investigated using variable energy PALS. This study is the first reported physical aging study using variable energy PALS. Previous work has typically been completed using films without well defined thermal histories. The concentration and average size of free volume elements were measured at 18 different energies, probing across the entire thickness of each sample. The data show the average free volume element size is reduced near the film surface (up to 50 nm deep) as compared to the interior of the film. Reduced free volume size near the surface indicates that the near-surface layer has aged more rapidly than the film interior. The overall free volume size decreases with aging, with no significant changes in their

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concentration. These results are consistent with accelerated physical aging in thin films tracked by gas permeability measurements. The influence of high pressure CO2 on the film free volume properties was also examined.

(1)Huang, Y.; Paul, D. R. Polymer 2004, 45, 8377- 8393.

(2)Mallon, P. E. In Positron & Positronium Chemistry; Jean, Y. C.; Mallon, P. E.; Schrader, D. M., Eds.: World Scientific, New Jersey, 2003; pp 253-280.

(3)Jean, Y. C.; Cao, H.; Dai, G. H.; Suzuki, R.; Ohdaira, T.; Kobayashi, Y.; Hirata, K. Applied Surface Science 1997, 116, 251-255.

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Gas Separation II – 4

Tuesday July 15, 4:00 PM-4:30 PM, Kaua’i

Gas Permeation Parameters and Other Physicochemical Properties of a Polymer With Intrinsic Microporosity (PIM-1)

P. Budd (Speaker), University of Manchester, United Kingdom - [email protected] N. McKeown, Cardiff University, United Kingdom - [email protected] B. Ghanem, Cardiff University, United Kingdom - [email protected] K. Msayib, Cardiff University, United Kingdom - [email protected] D. Fritsch, GKSS, Germany - [email protected] L. Starannikova, Institute of Petrochemical Synthesis, Russia - [email protected] N. Belov, Institute of Petrochemical Synthesis, Russia - [email protected] O. Sanfirova, Institute of Petrochemical Synthesis, Russia - [email protected] Y. Yampolskii, Institute of Petrochemical Synthesis, Russia - [email protected] V. Shantarovich, Institute of Chemical Physics, Russia - [email protected]

Polymers with intrinsic microporosity (PIMs) and PIM- polyimides form a new class of advanced materials for membrane gas separation. They are distinguished by several excellent properties: a good combination of permeability and permselectivity (the data points are above Robeson upper bounds for various gas pairs: O2/N2, CO2/CH4, CO2/N2), relatively high gas permeability (e.g. P(O2)=1600 Barrer), the largest reported gas and vapor solubility coefficients, large free volume, unusual possibility to control their transport parameters by film casting protocol, good film forming properties. In the presentation a survey of different transport and thermodynamic parameters in these polymers will be disclosed and discussed: relative contribution of solubility and diffusion coefficients to permeability, temperature dependence of the permeability coefficients, the effects of chloroform, methanol and water on the observed permeability, the results of the study of sorption thermodynamics in these polymers using the inverse gas chromatographic method, free volume study by means of positron annihilation lifetime spectroscopy.

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Gas Separation II – 5

Tuesday July 15, 4:30 PM-5:00 PM, Kaua’i

Addition-Type Polynorbornene with Si(CH3)3 Side Groups: Detailed Study of Gas Permeation and Thermodynamic Properties

L. Starannikova, Institute of Petrochemical Synthesis, Russia - [email protected] M. Pilipenko, Institute of Petrochemical Synthesis, Russia - [email protected] N. Belov, Institute of Petrochemical Synthesis, Russia - [email protected] Y. Yampolskii (Speaker), Institute of Petrochemical Synthesis, Russia - [email protected] M. Gringolts, Institute of Petrochemical Synthesis, Russia - [email protected] E. Finkelshtein, Institute of Petrochemical Synthesis, Russia - [email protected]

Polymerization of norbornene bearing Si(CH3)3 groups in the 5 position with the opening of double bonds results in creation of a novel high free volume, highly permeable polymer addition type poly(trimethylsilyl norbornene) (PTMSN). By accurate selection of the ratios catalyst/co-catalyst and monomer/catalyst the samples with increased molecular mass (about 400,000) and good film forming properties can be obtained. Transport parameters of PTMSN were measured using the gas chromatographic and mass spectrometric methods for different gases (H2, He, O2, N2, CO2, CH4, C2H6, C3H8, n-C4H10). Temperature dependence of the permeability coefficients (P) indicated that low activation energies of permeation (EP) and diffusion (ED) are characteristic for PTMSN. In some cases (CO2, C2H6) negative EP values were observed. Thermodynamics of vapor sorption in this polymer was studied using the inverse gas chromatography method. It was shown that PTMSN is characterized by very large solubility coefficients S similar to those of poly(trimethylsilyl propyne) (PTMSP). The comparison of the P, D, and S values of these highly permeable polymers showed that the greater permeability of PTMSP is determined by the larger D values. Application of different approaches for the determination of the size of microcavities in PTMSN indicated that this polymer is characterized by large size of microcavity (800- 1200 Angstroms3). Possible applications of this novel polymer as a material for gas separation membranes will be considered.

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Gas Separation II – 6

Tuesday July 15, 5:00 PM-5:30 PM, Kaua’i

Analysis of the Size Distribution of Local Free Volume in Hyflon® AD Perfluoropolymer Gas Separation Membranes by Photochromic Probes

J. Jansen (Speaker), ITM-CNR, Rende (CS), Italy - [email protected] E. Tocci, ITM-CNR, Rende (CS), Italy - [email protected] M. Macchione, Università della Calabria, Rende (CS), Italy - [email protected]

L. De Lorenzo, ITM-CNR, Rende (CS), Italy - [email protected] M. Heuchel, GKSS Research Center, Teltow, Germany - [email protected] E. Drioli,ITM-CNR, Rende (CS), Italy - [email protected]

This paper reports on the first successful application of the photochromic probe technique for the evaluation of the free volume distribution (FVD) in the amorphous glassy perfluorpolymer Hyflon® AD, a copolymer of 2,2,4- trifluoro-5-trifluorometoxy-1,3-dioxole and tetrafluoroethylene. Hyflon AD is highly permeable to permanent gases, offering interesting perspectives for use in gas separation membranes [1,2], especially because of its high thermal, chemical, ageing and weather resistance and excellent inertness to most organic solvents. As in other amorphous perfluoropolymers [3], the high gas permeability of Hyflon is related to the high Fractional Free Volume (FFV), usually estimated by Bondi's group contribution method [1,4-6]. Besides the total FFV, knowledge of its distribution is important for the understanding of the transport properties of the Hyflon membranes.

The aim of the present work is to use the photochromic probe method and molecular dynamics (MD) simulations to determine the size distribution of local free volume elements in Hyflon AD membranes and to correlate this to their transport properties. Experimentally, photochromic probing is relatively simple compared to other probing methods, like 129-Xe NMR spectroscopy and Positron Annihilation Lifetime Spectroscopy (PALS). It is based on the principle that photo-isomerizable molecules require a certain free volume to undergo isomerisation when dispersed in the polymer matrix [7]. Using a series of probe molecules with different size, spectrophotometric analysis of the degree of isomerisation of each probe will yield the FVD.

In the case of perfluoropolymers a major technical difficulty is the sample preparation, because the hydrocarbon probe molecules are usually insoluble in the fluorinated solvent for the polymer and the polymer is insoluble in the solvent for the probes. The main challenge of the present work is therefore to find a suitable method to obtain a homogeneous dispersion of the dye molecules in Hyflon AD films, to be subjected to subsequent spectrophotometric analysis. It

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will be shown that homogeneous films could be obtained successfully by the clever choice of mutually miscible fluorinated and non-fluorinated solvents.

Dense membranes, doped with a series of stilbene and azobenzene photochromic probe molecules with different sizes, were thus prepared by solution casting. The cis-trans isomerisation reaction was found to be completely reversible and repeatable over numerous cycles when irradiating at 440 nm and 350 nm, respectively. The ratio of the degree of probe isomerisation at the photostationary state in the solid polymer film, compared to that in a solution, is a quantitative measure of the availability of free volume elements of the corresponding size. A plot of this ratio as a function of the total isomerisation volume of the probe molecules represents the FVD in the polymer. For two different grades of Hyflon AD the experimentally determined FVD curve shows a typical sigmoidal shape. The free volume size ranges from about 250 to 520 Å3 in Hyflon AD60X and from about 380 to 600 Å3 in Hyflon AD80X. This is in agreement with the higher gas permeability of Hyflon AD80X and with data obtained by 129-Xe NMR spectroscopy and PALS. For the molecular dynamics simulations, several independent atomistic bulk models were constructed. The cavity size distribution was investigated by the particle insertion grid method [8]. It will be shown that the molecular modelling approach offers additional insight into the free volume distribution compared to the experimental method, for instance on the pore-interconnectivity.

References 1. R.S. Prabhakar, B.D. Freeman, I. Roman, Macromolecules, 37 (2004) 7688. 2. M. Macchione, J.C. Jansen, G. De Luca, E. Tocci, M. Longeri and E. Drioli, Polymer 48 (2007) 2619. 3. T.C. Merkel, I. Pinnau, R. Prabhakar, B.D. Freeman, Gas and Vapor transport properties of perfluorpolymers, in: Yu. Yampolskii, I. Pinnau, B.D. Freeman, B.D. (Eds.), Materials Science of Membranes for Gas and Vapor Separation, John Wiley & Sons, Chichester, 2006, pp.251-270. 4. V. Arcella, P. Colaianna, P. Maccone, A. Sanguineti, A. Gordano, G. Clarizia, E. Drioli, J. Membr. Sci., 163 (1999) 203. 5. A. Bondi, J. Phys. Chem., 68 (1964) 441. 6. D.W. van Krevelen, Properties of Polymers, Elsevier, Amsterdam, 1976. 7. J.G Victor, J.M. Torkelson, Macromolecules 20 (1987) 2241. 8. D. Hoffmann, M. Heuchel, Yu. Yampolskii, V. Khotimskii, V. Shantarovich, Macromolecules, 35 (2002) 2129.

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Drinking and Wastewater Applications II – 1 – Keynote

Tuesday July 15, 2:15 PM-3:00 PM, Maui

Analysis of RO Membrane Performance for Municipal Wastewater Treatment

C. Bartels (Speaker), Hydranautics, Oceanside, California, USA - [email protected] R. Franks, Hydranautics, Oceanside, California, USA - [email protected] P. Gourley, Hydranautics, Oceanside, California, USA - [email protected]

Reclamation of wastewater has become a key means to augment local water supplies in water stressed areas. Reclamation technology varies from conventional filtration and UV- advanced oxidation processes to membrane processes combined with UV and advanced oxidation processes. The selection of the type of process depends on the planned use of the reclaimed water. For indirect potable and industrial use, reverse osmosis (RO) has proven to be an essential wastewater treatment technology. RO membranes are a physical barrier that can ensure the significant reduction of dissolved inorganic solids, total organic carbon (TOC), pharmaceuticals, endocrine disruptor compounds (EDC), and other potentially harmful chemicals. The effective pore size of RO membrane is on the order of a few angstroms or molecular weight cut-off values on the order of 70 Daltons. As a result of the large number of plants using RO, there is a growing amount of detailed information about the removal rates of these compounds. Experience has shown that there are two critical parameters which determine if the effectiveness of the membrane system - stable water permeability and high rejection of contaminants. This paper will present analysis of these factors from a variety of operating plants.

A typical advanced wastewater treatment plant may consist of activated sludge treatment process, UF or MF membrane treatment, RO, and then UV and/or advanced oxidation process. To achieve stable RO operation, the plant must be operated within certain defined guidelines. Some of the key parameters include operating at a flux of 10-12 gfd, a recovery of 75-80%, maintaining a chloramine residual of 2-4 ppm, and utilization of RO membranes that show resistance to organic fouling. When the system is operated well, it is possible to achieve 3 to 6 years of membrane life.

Even when systems are operated with careful attention to detail and within recommended guidelines, it is still certain that their will be fouling. Due to the broad variety and complexity of organic compounds, there are many compounds

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which can adsorb on the surface of the membrane and reduce water flow. In a typical RO plant, the normalized flow may drop by 15 to 25% in the first 60 days of operation. In subsequent months, though, the decline may only be a few percent. Cleaning can often recover a good portion of this loss. Detailed operating data will be shown to examine this.

Although much progress has been made in controlling fouling, further research is needed to understand and minimize this fouling. This paper will present some detailed studies of membranes analyzed during the initial 30 days of operation and characterize the organic material which leads to membrane fouling. It will also evaluate common foulants found in commercial systems that can degrade membrane performance.

High rejection of contaminants is the key to the use of RO processes. The membrane which is selected must produce water that meets the water quality targets. Depending on the use of the water, these targets can vary significantly. For applications such as those in Singapore where the water is primarily used in the wafer fabrication industry, it is critical to have low concentrations of organics, as well as hardness and other salts. These very strict limits cannot be met by all membranes. Typically, high rejection, low pressure composite polyamide membranes, such as the Hydranautics ESPA2 membrane, have found much use, since they give adequate rejection and operate at the lowest possible pressure.

A recent survey of commercial plants shows that hardness ions are very highly rejected, with rejections ranging from 99.88 to 99.99%. Similar rejection would be seen for most ionized metals such as iron or manganese. Likewise the divalent, negatively charged sulfate molecule has similar rejection rates. Monovalent ions such, as sodium and chloride, have much lower rejection rates, in the range of 99 to 99.3%, and nitrate, which has a smaller hydrated radius, is the lowest rejected anion, at about 94-97% rejection. These rejection rates are still much higher than the values seen for brackish water treatment. Rejection of TOC is mostly in the range of 99.6 to 99.7%. This is important for places such as Singapore, where the permeate must contain less than 100 ppb of TOC. It is apparent, that these membranes can easily achieve such values for a feed stream containing 10-15 ppm of TOC. From recent plant data, a detailed analysis of the rejection of various compounds will be presented, and how these are meeting the recent stringent demands of the end user.

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Drinking and Wastewater Applications II – 2

Tuesday July 15, 3:00 PM-3:30 PM, Maui

Adsorption Behavior of Perfluorinated Compounds on Thin-film Composite Membranes

Y. Kwon (Speaker), Stanford University, Palo Alto, California, USA - [email protected] K. Shih, University of Hong Kong, Hong Kong, China C. Tang, Nanyang Technological University, Singapore J. Leckie, Stanford University, Palo Alto, California, USA

Perfluorinated compounds (PFCs), emerging contaminants, are globally distributed due to their persistent and bioaccumulative characteristics. The static adsorption behavior of PFCs on BW30, NF90, and NF270 membranes and the effect of the physico-chemical properties of the membranes and structure of Perfluorinated compounds (PFCs) on interactions between them have been thoroughly investigated. Two classes of PFCs were evaluated: perfluorosulfonic acid (PFOS) and perfluoroalkanoic acid with 5, 7, 9, and 11 carbon atoms.

Adsorption of PFCs increased with increasing ionic strength, and decreasing pH due to decreased electrostatic repulsion between membrane surfaces and PFCs. The extent of PFOS adsorption on each membrane was higher than the extent of comparable perfluorononanoic acid (PFNA) adsorption. This is attributed to the easy migration of PFOS to the membrane surface from aqueous solution compared with PFNA. The adsorption of PFCs on thin-film composite membranes strongly depended on the material composing the active layer of the membranes. NF270 membranes (a piperazine based membrane) showed higher adsorption of PFOS and PFNA compounds compared with BW30 and NF90 membranes (polyamide based membranes). The BW30 polyamide membrane, which has a coating layer with aliphatic carbon and hydroxyl groups, had less interaction with PFOS and PFNA than the NF90 polyamide membrane. Increased chain length of PFCs increased adsorption.

This research shows that the adsorption behavior of PFCs on commercial thin-film composite membranes depends on the electrostatic interaction of both membranes and PFCs as a function of the applied solution chemistry, the active layer material of the membranes, and the chain length/functional group of PFCs.

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Drinking and Wastewater Applications II – 3 Tuesday July 15, 3:30 PM-4:00 PM, Maui

RO Reject Recovery - A Challenge Towards Sustainable Water Reclamation

B. Viswanath (Speaker), CAWT, Singapore Utilities International Pte Ltd, Singapore - [email protected] G. Tao, CAWT, Singapore Utilities International Pte Ltd, Singapore - [email protected] K. Kekre, CAWT, Singapore Utilities International Pte Ltd, Singapore - [email protected] H. Ng, Env. Sci. & Eng. Division, National University of Singapore, Singapore L. Lee, Env. Sci. & Eng. Division, National University of Singapore, Singapore - [email protected] H. Seah, Public Utilities Board of Singapore, Singapore - [email protected]

Recovery of RO reject is an important part in sustaining the water reclamation practices. RO reject generated from water reclamation contains high concentration of both organic and inorganic compounds. Cost-effective technologies for treatment of RO reject are still relatively unexplored. This study aims to determine a feasible treatment process for removal of both organic and inorganic compounds in RO reject generated from NEWater production. NEWater is treated used water that has undergone stringent purification and treatment processes using advanced dual-membrane (microfiltration and reverse osmosis) and ultraviolet technologies. With the increasing demand of NEWater, the amount of brine generated will also be increased. It is therefore envisaged that there will be a need to treat the brine stream generated, at a later stage, before it is being discharged it to sea.

The organics present in the RO reject are soluble microbial products (SMPs), which comprises of mainly extra-cellular polymeric substances (EPS), such as polysaccharides and proteins. For reject disposal in inland water bodies, these organics have to be removed prior to discharge. Currently, there is little knowledge on (i) the characteristics of SMPs in the RO reject, and ii) effective technology for removal of the moderate to high concentration of organics present in the reject (brine). Besides organics, inorganic compounds with total dissolved solids (TDS) concentration typically higher than 2,000 ppm have to be removed too prior to reject disposal. Cost-effective technologies for treatment of RO reject are still unexplored. The reject generated from water reclamation contains both moderate to high concentration of organics and inorganic compounds. The reverse osmosis (RO) process has been a widely applied technology for water reclamation of secondary effluent due to its affordable cost and reliability. High quality permeate suitable for indirect potable or direct non-potable use after disinfection is produced from RO process while another stream, RO reject, is also generated simultaneously. The aim of this study is to determine the feasibility of the combined BAC and CDI process for removal of both organic and inorganic compounds in RO reject generated from NEWater production.

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The integrated system comprises of a biological activated carbon (BAC) column for organic removal, followed by capacitive deionization (CDI) process with and without microfiltration/ultrafiltration as the pre-treatment step for the CDI process. The biological activated carbon (BAC) process consists of both activated carbon adsorption and biodegradation of organics by microorganisms. The advantages of combining adsorption and biodegradation in BAC are: activated carbon can be partially regenerated by biochemical activities while the carbon bed is in operation (Rodman et al., 1978; Rice and Robson, 1982); less biodegradable organics can be adsorbed on the carbon first, and are then slowly degraded by microorganisms (Weber and Ying, 1978; Rice and Robson, 1982); and biological reaction rates become higher on activated carbon due to an enrichment of the organics by carbon adsorption (Weber and Ying, 1978). With these characteristics, BAC may be potentially useful for removal of organics in RO reject, which consists of less biodegradable organics.

The CDI process cycle consists of purification phase, regeneration phase and purge phase. During purification phase, an electrical field with a potential difference of about 1.2 - 1.5 volts (direct current) between the two electrodes removes the dissolved ions from the water as its passes through the electric field. The anions and cations are attracted to the opposite charge and directed to the respective electrode until saturation occurs. During purification phase, permeate with lower conductivity is generated as product water. Regeneration then takes place by reversing the potential. Hence, the ions are expelled into the rinse water and eventually purge out from the cell into a concentrate stream. In practice, more than 80% of water can be recovered with CDI process. CDI process generally has lower energy consumption as compared with membrane process as high pressure pumps are not required to achieve the treatment process in.

This study will provide an alternative treatment technology for water utilities to manage the brine streams generated from their water reclamation systems. This process shows the potential of increased water recovery in the reclamation process while volume for disposal can be further minimized.

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Drinking and Wastewater Applications II – 4

Tuesday July 15, 4:00 PM-4:30 PM, Maui

Effects of Organic Fouling on the Removal of Trace Chemicals in Nanofiltration Membrane Processes

S. Foo, University of New South Wales, Sydney, Australia J. Mcdonald, University of New South Wales, Sydney, Australia J. Drewes, Colorado School of Mines, Colorado, USA L. Nghiem, University of Wollongong, Wollongong, Australia S. Khan, University of New South Wales, Sydney, Australia P. Le-Clech (Speaker), University of New South Wales, Sydney, Australia - [email protected]

Trace chemicals, like endocrine disrupting compounds (EDCs), pharmaceutically active compounds (PhACs) and personal care products (PCPs), present in wastewater effluents are known to potentially cause detrimental effects to human health and to the biotic environment if not removed during the treatment process. High-pressure membrane processes such as nanofiltration (NF) can be used efficiently in applications where a high water quality is required. Previous research indicated that the fouling layer formed on the membrane surface during filtration could significantly affect the rejection of trace chemicals and could either improve or jeopardize the quality of the treated water. Conflicting results on the exact effect of fouling on rejection have indeed been reported and the mechanisms and physicochemical interactions occurring during the rejection of the trace chemicals by fouled NF membrane are, so far, limited.

Accelerated organic fouling was achieved on a NF270 membrane (from DOW) by using a variety of natural organic matter (NOM) fractions ranging from humic acids, extracted from river water and from soil, surface water, protein (bovine serum albumin) solution, and wastewater effluent from a tertiary treatment process (membrane bioreactor). Different concentrations of NOM and operating modes (such as constant flux and constant pressure operation) were considered. A mixture of 18 trace chemicals representing a wide range of different physicochemical properties was added at the nanogram per liter (ng/L) range to the different feed water qualities and their level of rejection was assessed by a gas chromatography-mass spectrometry (GC-MS). According to their characteristics, the trace chemicals were grouped into three categories: (1) hydrophilic non-ionic, (2) hydrophilic ionic, and (3) hydrophobic non-ionic. Variations in hydraulic resistance, membrane surface charge, roughness and relative hydrophobicity were measured for each experiment. Preliminary results indicated that the feed matrices and operational modes were the major factors governing the trace chemicals rejection. Under constant flux operation, it was found that the rejection of contaminants increased after fouling, as compared to those obtained under constant transmembrane pressure. Changes of the

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membrane surface characteristics due to the formation of an organic fouling layer were clearly confirmed by the observed increased hydrophobicity and decreased surface charge, which could explain the rejection mechanisms of compounds detected in this study: (1) the main rejection mechanism for the hydrophilic non-ionic compounds was size exclusion, as their rejection remains relatively constant throughout the experiments. (2) In the case of the hydrophilic ionic chemicals, the initial rejection mechanism was electrostatic exclusion, which became offset by size exclusion as fouling occurred. This was explained by the rejection performances of small compounds declining by 10%, while rejection of larger chemicals decreased only by 2%. (3) Hydrophobic non-ionic compounds presented high initial rejection due to their adsorption on the membrane surface. During long-term operation, their rejection decreased as they were able to diffuse through the hydrophobic fouling layer.

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Drinking and Wastewater Applications II – 5

Tuesday July 15, 4:30 PM-5:00 PM, Maui

Emergency Water Purification Device Using Gravity Driven Membrane Filtration

Y. Jiang (Speaker), University of Oxford, Oxford, United Kingdom - [email protected] Z. Cui, University of Oxford, Oxford, United Kingdom - [email protected]

An emergency water purification device capable of purifying water to potable standard after natural disasters, such as floods, has been developed in this study. This device is based on ultrafiltration (UF), and the filtration is driven by gravity and hence no external power is required for the operation.

The paper reports results from prototype testing. A commercial hollow fiber UF cartridge was used in this study. Key design papameters were first identified and their effect on membrane performance was tested experimentally, including feed flowrate, membrane mounting angle, transmembrane pressure (TMP) and feed concentration, etc. A pure water flux of around 14 l/m2h has been obtained under 0.1 bar, approximate pressure generated by 1 m water head. This shows that the selected cartridge has great potential to meet drinking water requirements in emergencies and the gravity driven concept could be feasible. Additionally, through filtration tests of betonite solutions, the flux dependency on TMP and feed concentration were determined. It was also found that the cartridge placed vertically performed well giving higher permeate flux over longer period of time.

Based on the obtained design parameters, a laboratory prototype, which generated TMP by water gravity, was fabricated to further confirm and optimize the design and operation. Experiments on the behavior of gravity driven feed flowrate, fouling tendency over time, the effect of manual backflushing on permeate flux and device lifetime, etc. were carried out. The investigation of 8-hour fouling tendency of this cartridge using diverse concentration betonite solutions shows that manual backflushing with the treated water is needed for high productivity and will perform better if applied in the first couple of hours. An optimal backflushing scheme was determined. It was confirmed that the device can produce 8 l portable water per hour on average. This is enough to meet drinking water needs of a group up to 30 people every day. Additionally, a long term test demonstrates that the device can repeat its performance every day by simple manual backflushing for at least 30 days.

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Drinking and Wastewater Applications II – 6

Tuesday July 15, 5:00 PM-5:30 PM, Maui

Membrane Defects and Bacterial Removal Efficiency: Effect of Alterations of the Skin and of the Macroporous Support.

N. LEBLEU (Speaker), Université de Toulouse, Toulouse, France - [email protected] C. CAUSSERAND, Université de Toulouse, Toulouse, France - [email protected] C. ROQUES, Université de Toulouse, Toulouse, France - [email protected] P. AIMAR, Université de Toulouse, Toulouse, France - [email protected]

In the context of potable water production, one of the major concerns to water treatment remains the microbiological water safety which is ensured by final disinfection step. In principle and according to its membrane pore size distribution, ultrafiltration is able to remove very efficiently waterborne pathogens and thus to meet drinking water requirements. Nevertheless, that may not be the case any more if membrane integrity is compromised. As for an example, imperfections may be generated during membranes manufacturing (such as abnormally large pores) or the membrane porous structure may be altered overtime by chemical and mechanical ageing [1,2]. In function of their characteristics (number, size, depth,&), such imperfections are likely to allow microogarnisms through the membranes [3,4].

The objective of the work presented here is to address, via an experimental study, the following question : which characteristics of such defects allow bacterial leakages and lead to the contamination of the distributed water ?

Challenge tests were performed on flat-sheet regenerated cellulose membrane the integrity of which was deliberately altered. The MWCO of the uncompromised membrane is 30 kD and its effective area is 13.4 cm2. These membranes were chosen for their asymmetrical structure (skin with low porosity and macroporous support) and because they are initially totally retentive for E. coli. In such conditions, bacterial concentration in permeate samples is directly linked to their transfer through the defect. The membrane porous structure was altered by perforating the surface by means of various techniques, depending on the required characteristics of the defect. At first, defects of 200 µm diameter with a perfect cylindrical geometry were created with ultrashort laser pulses. Then, in order to approximate those which are more likely to be generated during membrane ageing, holes of same diameter were punched with a sharp tungsten tip. Finally, a microhardness tester allowed us to create defects across one fraction of the membrane skin thickness. Once these imperfections have been made, dead-end filtration experiments were carried out in a stirred cell device. The feed solution consists of a bacterial suspension of E. coli at 104 CFU/mL and the transmembrane pressure was set to 0.5 bar. Steadily, permeate samples

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were collected, the viable bacteria were enumerated. Influence of the characteristics of the defect upon the microorganism retention, i.e. the log reduction value (LRV), was analysed in order to assess the impact of a defect which alters only the skin in comparison with a defect crossing the whole membrane structure.

Experimental results confirmed the leading part of the selective skin towards bacterial removal : as long as the selective skin is not altered on its whole thickness, the altered membrane keeps a retention efficiency equivalent to the one of an uncompromised membrane (LRV > 7). Nevertheless, the skin is not the only part of the membrane occuring in the retention mechanisms. For membranes with a fully punched skin but with an uncompromised macroporous support, the bacterial tranfer through the defect is highly limited by the support since a log reduction value of 4 log may be attributed to this part of the membrane structure. In order to get a better understanding of the retention mechanisms provided by the macroporous support, a comparison between the two types of defects altering the whole thickness of the membrane was done. Here, the log reduction value is around 2 log when the support was punched by the tip to be compared to 0.3 log in the case of a membrane altered with a defect of same diameter made by burning the whole support with the femtosecond laser beam. The observed discrepancy between those two results is analysed as the swelling of the macroporous structure under the selective skin owing to the applied transmembrane pressure. This change in material structure leads to the partial clogging of the punched defect which was confirmed by scanning electron microscopy observations. Under such conditions, we conclude that the macroporous support works as quite an efficient fibrous particles collector.

To conclude, a highly compromised membrane (one defect of 200 µm diameter for an effective area of 13.4 cm2) is likely to keep a non negligible bacterial removal efficiency thanks to the part taken by the macroporous support in bacteria retention mechanisms. To complete this study, experiments with smaller defects are still in progress. However, by gradually decreasing the size of the defects until the range of the microorganisms size, we will have to cope with bacterial specific behaviour such as their deformation under mechanical stress.

References

[1] Kobayashi et al. 1998 J Membr Sci vol.140 p.1.

[2] Causserand et al. 2006 Desal vol.199 p.70.

[3] Urase et al. 1996 J Membr Sci vol.115, p.21.

[4] Gitis et al. 2006 J Membr Sci vol.276 p.199.

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Inorganic Membranes I – 1 – Keynote

Tuesday July 15, 2:15 PM-3:00 PM, Moloka’i

Inorganic Membranes also Swell

M. Yu, University of Colorado, Boulder, Colorado, USA J. Lee, University of Colorado, Boulder, Colorado, USA H. Funke, University of Colorado, Boulder, Colorado, USA R. Noble, University of Colorado, Boulder, Colorado, USA J. Falconer (Speaker), University of Colorado, Boulder, Colorado, USA - [email protected]

MFI zeolite membranes swell when some molecules adsorb in the MFI pores. Although the amount of swelling is small compared to polymer membranes, it has dramatic effects on the membrane permeation and separation properties. Adsorbate-induced swelling can essentially seal off defects in MFI membranes. Thus, MFI membranes with significant flow through defects can be selective for some separations because certain molecules, when they adsorb in the MFI pores, expand the crystals and shrink the defect pores. This adsorbate-induced swelling dramatically changes the membrane permeation properties. A combination of permporosimetry, pervaporation, vapor permeation, single gas permeation, and binary mixture separations were used to demonstrate these behaviors on membranes with different fractions of their flow through defects. Permporosimetry measurements, in which the flux of helium was measured as a function of the activity of a molecule adsorbed in the MFI pores, depended on which molecule was adsorbed.

A membrane that had 90% of its flow through defects at room temperature, as determined by benzene permporosimetry, had an H2/SF6 ideal selectivity of 250. For the same membrane, n-hexane permporosimetry showed that only 0.14% of the helium flux at room temperature was through defects. Thus, MFI membranes can be self-sealing for many separation mixtures. The sizes of the defects were estimated from capillary condensation to be approximately 2 nm in this membrane, but this size decreased dramatically following adsorption of some molecules, such as n-hexane. These measurements show that many of the techniques that have been used for MFI membrane characterization in previous studies do not determine if the membrane has significant flow through defects. Permporosimetry with n-hexane, H2/SF6 and n-butane/i-butane ideal selectivities, n-propane/H2, n-butane/i-butane, and n-hexane/2,2-dimethylbutane separation selectivities have all been used to estimated membrane quality. However, all these methods used molecules that cause MFI crystal expansion, and thus these methods do not provide an good indication of membrane quality. Instead, pervaporation of molecules too large to fit into MFI pores (such as isooctane and 2,2-dimethylbutane), vapor permeation of these molecules as a function of feed

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pressure, and permporosimetry with benzene present a consistent picture of membrane properties.

Permporosimetry, temperature-programmed desorption, and pervaporation of mixtures clearly show that propane, n-butane, i-butane, n-pentane, n-hexane, n-octane, and SF6 all decrease the size of defects in MFI membranes by swelling MFI crystals when they adsorb. Although XRD and optical microscopy studies show that crystal expansion is less than 0.5% linearly for MFI crystals, such expansion can essentially seal 2-nm membranes. For the membrane with 90% of its helium flow through defects, n-hexane adsorption decreased the helium flow almost three orders of magnitude. This membrane also had a 2,2-dimethylbutane flux during pervaporation that was 160 times its n-hexane flux; that is, the larger molecule permeated 160 times faster because the defects that it permeated through were almost sealed off by n-hexane adsorption. The defects were sealed at much less than saturation loadings in the MFI crystals. The loading required to decrease the flux through defects by more than two orders of magnitude increased as the number of carbon atoms in the alkane decreased. These results may explain many inconsistencies for MFI permeation in the literature. They also indicate that flow through defects can be more important at higher feed concentrations, and show that characterizations at high feed concentrations provide a better indication of membrane quality.

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Inorganic Membranes I – 2

Tuesday July 15, 3:00 PM-3:30 PM, Moloka’i

Synthesis and Characterization of SAPO-34 Zeolite Crystals and Membranes Employing Crystal Growth Inhibitors

S. Venna, University of Louisville, Louisville, Kentucky, USA M. Carreon (Speaker), University of Louisville, Louisville, Kentucky, USA - [email protected]

The separation of CO2 from natural gas is an important environmental and energy issue. Improved membranes for separating CO2 from CH4 would reduce considerably the costs of natural gas purification. Since polymeric membranes have limitations based on operating temperature and high pressures that cause their degradation, small pore zeolites such as SAPO-34 with pore size ~0.38 nm are preferred to effectively separate CO2/CH4 mixtures. Here, we present the hydrothermal synthesis of SAPO- 34 employing crystal growth inhibitors (CGI) such as polyoxyethylene lauryl ether, polyethylene glycol, and methylene blue for both crystal and membrane preparation. The incorporation of these CGI during gel synthesis resulted in 1-2.5 ¼m seeds with narrow crystal size distribution and unprecedented high surface areas (up to 700 m2/g). CO2 and CH4 adsorption isotherms indicated improved CO2/CH4 selectivities for the crystals prepared with CGI. Membranes were grown by in-situ crystallization on ±-alumina porous tubes and evaluated for CO2/CH4 gas separation.

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Inorganic Membranes I – 3

Tuesday July 15, 3:30 PM-4:00 PM, Moloka’i

Effects of Electroless Plating Conditions on the Synthesis of Pd-Ag Hydrogen Selective Membranes

R. Bhandari (Speaker), Worcester Polytechnic Institute, Worchester, Massachusetts, USA - [email protected] Y. Ma, Worcester Polytechnic Institute, Worchester, Massachusetts, USA - [email protected]

Pd-Ag membranes are better suited for H2 separation applications than pure Pd membranes because of their higher H2 permeability (23 Ag wt%). The morphology of the Pd-Ag deposits plays an important role in the synthesis of a thin H2 selective membrane. The electroless plating conditions have radical effects on the deposit morphology. The electroless deposition involves redox reactions, therefore electrochemical technique such as linear sweep voltammetry (LSV) could be very useful to understand the effect of the plating conditions on the deposit morphology. The objective of this study was to investigate the plating conditions and their effect on the morphology of the deposits using the LSV technique in order to determine suitable plating conditions to synthesize H2 selective Pd-Ag membranes.

The electroless plating bath used in this study consisted of Pd or Ag ions and N2H4 as the reducing agent and porous stainless steel coupons were used as the substrate. The deposits were characterized by using SEM, EDX and X-ray differactometer. The stainless steel wires deposited with Pd or Ag were used in the LSV study. The LSV scans were obtained using the BAS 110B/W electrochemical station. Based on the results of LSV study, two Pd-Ag membranes (M-1 and M-2) supported on porous Inconel tubes were synthesized using the multilayer Pd-Ag sequential deposition and then annealed at 550 °C (24 h) in H2 atmosphere and characterized further for the H2 permeation in 300-500 °C range.

The Ag bath LSV polarization curve showed the fast reduction kinetics for the metal and within 15-25 mV electrode over potential, the overall deposition process was limited by the diffusion of Ag ions in the solution. However large over potential (400- 500 mV) was observed for the Pd deposition. Also the Pd surface showed higher catalytic activity for the N2H4 oxidation and at electrode potential of 0 mV, the current associated with the oxidation of N2H4 on the Pd surface was an order of magnitude higher than that on the Ag surface. The morphology study of the Pd deposits (N2H4/Pd = 5.6/16) showed good Pd pore penetration. However for the Ag deposits (N2H4/Ag = 5.6/3), poor Ag pore penetration was observed. Further, the Ag deposits (N2H4/Ag = 5.6/3) showed dendritic morphology on the substrate covered with the Pd deposits, therefore

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not suitable for the Pd-Ag membrane synthesis. The poor penetration of the Ag deposits (N2H4/Ag = 5.6/3) could be due to the overall Ag deposition significantly controlled by the diffusion of Ag ions in the solution. Therefore, the lower N2H4/Ag ratio in the bath (N2H4/Ag = 4/20) could avoid Ag deposition occurring at electrode potential where overall deposition was controlled by the diffusion of Ag ions. The deposits obtained with (N2H4/Ag = 4/20) showed good pore penetration and no dendritic characteristics, therefore suitable for the synthesis of Pd-Ag membrane.

Both the Pd plating condition with N2H4/Pd = 5.6/16 and Ag plating condition with N2H4/Ag = 4/20 showed deposits with uniform growth and good pore penetration and hence were used to synthesize the Pd-Ag membranes.

Negligible He flow was observed for as synthesized membranes (M-1 thickness = 7.4 µm, M-2 thickness = 8.8 µm). After annealing at 550 °C both membranes showed increase in the H2 permeance due to the alloying of Pd-Ag layers. The membranes after annealing showed low activation energy (AE) for the H2 permeation (M-1 = 3.2 kJ/mole, M-2 = 8.6 kJ/mole) than pure Pd (14.9 kJ/mole). The H2 permeability was product of its diffusivity and solubility in Pd. The alloying of Pd with Ag decreased the H2 diffusivity and increased the H2 solubility in Pd. The net effect was increase in the H2 permeance and corresponding decrease in the AE for H2 peremance up to 23 wt% Ag. The low AE of Pd-Ag membranes indicated that the H2 permeability in Pd-Ag membranes decreased at lesser rate than that of Pd, making Pd-Ag membranes more effective for the H2 separation at lower temperatures. The M-1 showed the H2 permeability (m3-µm/m2-h-atm0.5) of 466, 428 and 366 while the corresponding pure Pd foil values were 525, 374 and 237 at 500, 400 and 300 °C respectively. For the M-2, the H2 permeability values were 451, 348 and 245 m3-µm/m2-h- atm0.5 at 500, 400 and 300 °C respectively. The EDX analysis showed the average value of 20 and 31 wt% in M-1 and M-2 respectively. The lower H2 permeability of M-2 than that of M-1 could be attributed to its higher than optimum (23) Ag wt%. Both membranes showed decline in H2/He selectivity with time with the final selectivity (ΔP=1atm) of 335 (M-1) and 151 (M-2) at 500 °C.

It can be concluded that thin and He dense Pd-Ag membranes could be synthesized using the suitable plating conditions based on the LSV study. The annealing time of 24 h at 550 °C was sufficient to form the Pd-Ag alloy. The prepared membranes were more effective for H2 separation than the pure Pd membranes at lower temperatures.

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Inorganic Membranes I – 4

Tuesday July 15, 4:00 PM-4:30 PM, Moloka’i

Upgrading of a Syngas Mixture for Pure Hydrogen Production in a Pd-Ag Membrane Reactor

A. Brunetti, National Research Council - Institute for Membrane Technology, Rende (CS), Italy - [email protected] G. Barbieri (Speaker), National Research Council - Institute for Membrane Technology Rende (CS), Italy - [email protected] E. Drioli, University of Calabria, Rende CS, Italy, [email protected]

In integrated plants for hydrogen production a fundamental step is the upgrading of stream outletting reformers. These streams contain H2 (50%), CO2, N2 etc. and about 10-15% of CO which could be converted producing in the meantime more hydrogen. In a traditional reactor (TR), the presence of hydrogen in the feed stream depletes CO conversion owing to the constraint imposed by the thermodynamics. In the temperature range of interest (220-330°C) the maximum achievable conversion could not be higher than 25%. In Pd-Ag membrane reactor (MR), the selective removal of hydrogen allows the thermodynamics limitation of a TR to be overcome and hence CO conversion might be significantly higher. This value depends on the MR extractive capacity which is a function of the operating conditions and particularly of the permeation driving force. In this work it was realized by feed and permeate pressures and no sweep gas was used. CO conversion in this MR was measured 4-5 times higher than that of equilibrium of a TR. Hydrogen recovered as a pure permeate stream is about 80% of the total present in the feed stream and also produced by (water gas shift) reaction. The hydrogen produced was fed to a PEMFC for energy production which showed stable performance not depending on the MR operating conditions and equal to that measured feeding hydrogen from a cylinder.

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Inorganic Membranes I – 5

Tuesday July 15, 4:30 PM-5:00 PM, Moloka’i

Preparation and Characterization of Hollow Fibre Carbon Membranes based on a Cellulosic Precursor

X. He (Speaker), Norwegian University of Science and Technology, Norway - [email protected] J. Lie, Norwegian University of Science and Technology, Norway - [email protected] E. Sheridan, Norwegian University of Science and Technology , Norway- [email protected] M. Hägg, Norwegian University of Science and Technology, Norway - [email protected]

A selected cellulosic precursor was spun as hollow fibres based on the dry-wet spinning method. The influences of the different variables in the spinning process on the final quality of the fibre were studied and discussed (spinning rate, coagulation bath temperature, air gap, take-up speed, and others). Documentation of the quality of the resulting fibres was done by SEM-pictures. The carbon membranes were fabricated from the cellulosic fibre precursor under a multi-dwell carbonization protocol with inert purge gas, a heating rate of 1°C/min and a final temperature and soak time of 650°C and 2h, respectively. A weight loss of approximately 75% and a longitudinal shrinkage of 32% were found. The structure and morphology of the prepared hollow fibre carbon (HFC) membranes were also characterized by SEM. The diameter and thickness of the HFC membranes were identified by an optical microscope. The HFC membranes were mounted in a module for testing, and five different gases (H2, N2, CH4, CO, CO2) were measured using a single gas permeation test setup. The permeation tests of the HFC membranes were run at the same feed temperature and pressure (30°C and 2bar). Four different recipes were used for post-treatment of the hollow fibre precursors before carbonization. The results indicated clearly the relationship between the separation performance and the post-treatment conditions of the fibres. The separation performance of the HFC membranes could thus be optimised with respect to the conditions for the post-treatment of the hollow fibres. The permeance (m3(STP)/m2.h.bar) for H2 and CO2 was 0.045 and 0.006 respectively, and the ideal selectivity for the gas pairs CO2/N2, CO2/CO and H2/CH4 was found to be 47, 19 and 2800. The five gases were chosen due to the potential of using this membrane for separation of pressurized flue gas (CO2-N2-CO), pre-combustion separation (CO2-H2 at high temperature and pressure) or upgrading of biogas (CO2-CH4). Further work on optimisation is ongoing to increase separation performance.

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Inorganic Membranes I – 6

Tuesday July 15, 5:00 PM-5:30 PM, Moloka’i

High-Density, Vertically-Aligned Carbon Nanotube Membranes with High Flux

M. Yu (Speaker), University of Colorado, Boulder, Colorado, USA - [email protected] H. Funke, University of Colorado J. Falconer, University of Colorado R. Noble, University of Colorado

Several studies have reported carbon nanotube (CNT) membranes that consist of aligned nanotubes sealed in a polymer or inorganic matrix1-3. These membranes had single gas selectivities that were approximately Knudsen, and they had high permeation fluxes for liquid and gas feeds in nanotubes. Because the aligned CNTs grew with a low density (~ 1011 CNTs per cm2 of surface area), only a few percent (0.08 ~ 2.7) of the membrane consisted of CNTs; most of it was the sealing material. Thus, although the fluxes per cm2 of CNT area were orders of magnitude higher than other types of membranes, the fluxes per actual membrane area (CNTs plus polymer or inorganic sealant) were much lower.

We have prepared vertically-aligned CNT membranes with a CNT density of 2.9 x 1012 CNTs/cm2, which is approximately 20 times higher than these previous studies by eliminating the need for a polymer or inorganic filler. Aligned CNTs were grown on a silicon wafer with catalyst thin films 1-nm Fe/10-nm Al2O3 that were formed by e-beam evaporation, the nanotubes were removed from the silicon surface by in-situ water etching, and the nanotubes were collapsed to about 5% of their original area by solvent evaporation. The tops of the CNT membrane are expected to be open due to water etching4, 5, and the bottoms are also expected to be open because the silicon wafers can be reused for several times for CNT growth after detaching the CNT arrays. This preparation is much simpler than that used for composite membranes, and the membranes have much higher fluxes because of the much higher CNT density and additional interstitial transport pathway between nanotubes. These membranes exhibit light gas selectivities that are equal to or greater than Knudsen selectivities, but their permeances are not independent of pressure. Instead, for most gases the permeances decrease with increasing pressure. The permeance at 1 bar pressure drop for N2 through a membrane that was 750 mm thick was 1.2 x 10-4 mol/m2-s-Pa. This corresponds to a permeability of 27 cc (STP)/ m2-s-atm. Thus, these permeabilities are one to four orders of magnitude higher than those reported for composite membranes.

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Because these membranes do not contain a filler, the spaces between the nanotubes must also be available for transport, but apparently the CNTs are close enough together that the flux through these spaces has similar behavior to the flux through nanotubes. The flux of liquid n-hexane through these membranes was approximately 1,500 kg/m2-h at 1 bar pressure drop, which is 3 to 4 orders of magnitude higher than the flux of n-hexane through MFI zeolite membranes, even though these membranes are thicker (750 mm). The nanotubes were approximately 3 nm in diameter, as determined by TEM and calculated from N2 desorption isotherms at 77 K. The average space between nanotubes is appropriately 3 nm with a distribution from 1.4 to 7 nm, as calculated by the BJH method from N2 desorption isotherms at 77 K.

1.Hinds, B. J.; Chopra, N.; Rantell, T.; Andrews, R.; Gavalas, V.; Bachas, L. G. Science 2004, 303(5654), 62-65. 2.Holt, J. K.; Park, H. G.; Wang, Y. M.; Stadermann, M.; Artyukhin, A. B.; Grigoropoulos, C. P.; Noy, A.; Bakajin, O. Science 2006, 312(5776), 1034-1037. 3.Kim, S.; Jinschek, J. R.; Chen, H.; Sholl, D. S.; Marand, E. Nano Lett 2007, 7(9), 2806-2811. 4.Ci, L. J.; Manikoth, S. M.; Li, X. S.; Vajtai, R.; Ajayan, P. M. Adv Mater 2007, 19(20), 3300-+. 5.Zhu, L. B.; Xiu, Y. H.; Hess, D. W.; Wong, C. P. Nano Lett 2005, 5(12), 2641-2645.

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Membrane Fouling - UF & Water Treatment – 1 – Keynote

Tuesday July 15, 2:15 PM-3:00 PM, Honolulu/Kahuku

Fouling Mechanisms and Fouling Control By Membrane Surface Modification in Ultrafiltration of Aqueous Solutions Containing Polymeric Natural Organic Matter

M. Ulbricht (Speaker), Lehrstuhl für Technische Chemie II, Universität Duisburg-Essen, Germany - [email protected] P. Peeva, Lehrstuhl für Technische Chemie II, Universität Duisburg-Essen, Germany - [email protected] H. Susanto, Lehrstuhl für Technische Chemie II, Universität Duisburg-Essen, Germany - [email protected]

Because membrane processes are increasingly used for separations of mixtures with high complexity, the focus of fouling studies in ultrafiltration (UF) has also been shifted from using well-studied foulants such as proteins [1], to more complicated and less-defined substances, i.e. colloidal natural organic matter (NOM) [2]. Relevant foulants in such systems are humic acids, polysaccharides or polyphenols. The strongest motivation for such work is certainly based on the success of membrane separations and membrane bioreactors (MBR) for water and wastewater treatment.

With respect to the identification of foulants for UF membranes, we had demonstrated that the combination of a detailed analysis of the membrane surface structure with adsorption and UF experiments can give valuable quantitative information about causes, extent and consequences of membrane fouling, also for previously less investigated foulants such as the polysaccharide dextran [3]. Surface modification of the membranes is gaining increasing importance for minimizing membrane fouling [4]. Very recently, new thin layer hydrogel composite (TLHC) UF membranes, based on commercial polyethersulfone (PES) membranes, have been prepared via photo- initiated graft copolymerization of monomers containing side groups with “kosmotropic” properties along with controlled chemical cross-linking during grafting. The antifouling properties of those new membranes had been evaluated using a limited set of adsorption and UF experiments with the model foulants myoglobin and humic acid [5]. TLHC membranes with adjusted surface chemistry had also shown promising performance in UF of NOM- containing water [6].

This work describes the fouling behaviour of protein, humic acid, polysaccharide, polyphenol and their mixtures by investigation of membrane-solute interactions (adsorptive fouling) and membrane- solute-solute interactions (UF fouling). Surface and fouling characterization was also supported by measurements of contact angle and zeta potential and by FTIR-ATR spectroscopy. Myglobin, bovine serum albumin, humic acid from Aldrich, alginate, dextran, and

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polyphenol from green tea (Sigma) were used as model foulants. Three commercial PES UF membranes with nominal cut-off of 10, 30 and 100 kg/mol and a TLHC membrane, synthesized by photo-initiated graft copolymerization of poly(ethylene glycol) methacrylate (PEGMA) onto the 100 kg/mol PES UF membrane and having a cut-off of 10 kg/mol (cf. [5]) were used. The effects of foulant concentration, pH, ionic content and proportions between different foulants in the solution onto fouling were investigated. The results showed that significant water flux reductions and changes in membrane surface property were observed after static adsorption for PES membranes for all feed solution conditions. At moderate concentrations (up to 0.1 g/L), the polyphenol was a strongest foulant. Synergistic effects between polysaccharide and protein with respect to forming a mixed fouling layer with stronger reduction of flux than for the individual solutes under the same conditions have also been verified for PES UF membranes. UF experiments using a stirred dead- end UF indicated that both reversible and irreversible fouling contributed to the overall fouling. Standard fouling models were used to distinguish between pore blocking and constriction, and cake formation. The water flux after UF and external washing for the PES membrane with a cut- off of 10 kg/mol was between 20 and 70% of the original water flux. The pronounced antifouling efficiency of the TLHC membrane has been demonstrated for the strong foulants polyphenol, alginate and the model proteins as well as for foulant mixtures, with respect to both adsorptive and ultrafiltration fouling. In particular, the regeneration of flux after UF was much easier, even simple external rinsing with water removed most of the fouling layer and lead to more than 90% of the original water flux.

The results of this work with respect of the individual and combined effects of polymeric model foulants for NOM and the high antifouling efficiency of tailored hydrogel-based composite membranes for UF have also implications for other applications of ultrafiltration, for instance in the food and beverage or in the pharmaceutical industries.

[1] R. Chan, V. Chen, J. Membr. Sci. 2004, 242, 169-188.

[2] A. R. Costa, M. N. de Pinho, M. Elimelech, J. Membr. Sci. 2006, 281, 716-725.

[3] H. Susanto, S. Franzka, M. Ulbricht, J. Membr. Sci. 2007, 296, 147-155.

[4] M. Ulbricht, Polymer 2006, 47, 2217-2262.

[5] H. Susanto, M. Ulbricht, Langmuir 2007, 23, 7818-7830.

[6] H. Susanto, M. Ulbricht, Water Research 2008, accepted.

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Membrane Fouling - UF & Water Treatment – 2

Tuesday July 15, 3:00 PM-3:30 PM, Honolulu/Kahuku

A Mechanistic Study on the Coupled Organic and Colloidal Fouling of Nanofiltration Membranes

A. Harris (Speaker), Rice University, Houston, Texas, USA, [email protected] A. Kim, University of Hawaii at Manoa, Honolulu, Hawaii, USA - [email protected] Q. Li, Rice University, Houston, Texas, USA - [email protected]

Various types of foulants present in natural and waste waters, such as colloids, dissolved organic matter, electrolyte ions, and microorganisms, contribute to membrane flux decline through different mechanisms. Separately the fouling mechanisms of each are relatively well understood, and models are available to predict respective fouling behaviors. However, little is understood about the interactions between these foulants and how they impact membrane fouling mechanisms in filtration of natural and waste waters. This study focuses on the coupled effect of dissolved organic and colloidal foulants on the permeate flux of nanofiltration (NF) membranes. The role of common organic macromolecules in natural and waste waters on the deposition of silica colloids on NF membrane surface was investigated.

Bovine serum albumin (BSA), sodium alginate, dextran, and a standard natural organic matter Suwannee River NOM were chosen to represent naturally occurring organic matter of different molecular properties in natural and waste waters. The impact of the model organic compounds on the physicochemical properties, i.e., particle size, surface zeta potential, and suspension stability, of silica colloids (60 nm in diameter) was thoroughly characterized by dynamic light scattering (DLS) and electrophoretic mobility measurements. The four model organic compounds showed distinct impact on silica-silica interactions. For example, measurements of colloidal silica properties in the presence of dextran showed little impact compared to silica alone, while BSA, alginate and NOM demonstrated different levels of impacts on silica colloid properties through adsorption onto the silica surface at sufficiently high concentrations. Quartz crystal microbalance with dissipation monitoring (QCM-D) was employed to quantitatively characterize particle-particle interactions in the presence and absence of the model organic compounds using a quartz crystal sensor coated with SiO2. The QCM-D technique was also used to quantify the impact of the model organic compounds on the deposition of the silica colloids on polymer surfaces with similar surface chemistry as the membranes. This technique was shown to be a useful tool for evaluating membrane fouling potential of a complex suspension. The effect of solution chemistry, e.g., pH and Ca2+ concentration, was also studied. The impact of Ca2+ was very complex due to its interaction with both the organic macromolecule and the silica colloid. Bridging between

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macromolecules adsorbed on neighboring silica colloid surface was hypothesized to be the cause of the greatly enhanced deposition of silica colloids in the presence of Ca2+. Monte-Carlo simulations of the BSA�silica system are currently being performed to better understand how BSA or other macromolecules affect silica aggregation and deposition behaviors.

Results from these molecular-level characterizations were combined with those from a series of cross-flow filtration experiments to reveal the mechanisms involved in the combined effect of model organic and colloidal foulants on NF flux decline. The enhanced deposition of silica colloids observed in the QCM-D experiments agreed well with the increased initial flux decline rate during cross-flow filtration of the colloid-organic mixture compared to the additive sum of the effects of the two individual foulants.

In addition to changing the deposition rate of silica colloids and hence increasing the initial fouling rate, adsorption of organic macromolecules also alters the structure of the colloidal cake layer. Transmission electron microscopy (TEM) imaging of fouled membranes was employed to visualize the structure of the fouling layer formed with and without the model organic macromolecules. This effect was manifested at a later stage of the filtration process. Although BSA was found to significantly increase initial membrane fouling rate, higher quasi-steady state flux was observed in the presence of BSA due to a more porous fouling layer.

Results from this study clearly demonstrate that different organic macromolecules affect colloidal fouling differently. The overall fouling potential of a complex suspension may not be predicted based on the fouling potential of each individual foulant.

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Membrane Fouling - UF & Water Treatment – 3

Tuesday July 15, 3:30 PM-4:00 PM, Honolulu/Kahuku

Effect of Crossflow on the Fouling Rate of Spiral Wound Elements

P. Eriksson (Speaker), GE W&PT, Vista, California, USA - [email protected]

Four spiral wound ultrafiltration elements (0.3 m (12”) long) operated on an oil/water emulsion for 140 h at 207 kPa (30 psi) feed gage pressure, each at a different feed flow rate, which corresponded to 0.1-0.4 m/s superficial velocities and 11-138 kPa/m (1.7-20 psi/m) pressure drops. The feed channel spacer was diamond shaped with a thickness of 0.86 mm (0.034”). During the first 3 hours of operation, the permeate flux vs. feed flow rate followed the normal curve for applications where the permeate flux at low crossflow rates is limited by the boundary layer resistance. The permeate flux increased from 28 lmh (17 gfd) at the lowest flow rate to 134 lmh (79 gfd) at the highest flow rate, with the slope of the flux vs. flow curve steepest at the lowest flow rate to almost level out at the highest flow rates. After 15 hours of operation the permeate flux had decreased 30-50 percent for the two middle flow rates and much less for the lowest and highest flow rates. This trend continued during the rest of the test, so at the end, the permeate flux was 9.3, 12, 21 and 77 lmh (5.5, 7.0, 12, and 46 gfd) for the respective element listed in order from the lowest to the highest feed flow rate. Between 55 to 79 hours operating time, the flow rate for the element with the lowest flow rate was temporarily increased to give a pressure drop of 115 kPa/m, which was between those for the two elements with the highest flow rates. This increased the permeate flux of the element to slightly above that of the initially next highest feed flow rate element, but the flux was still less than half of that of the element with the highest feed flow rate. These results imply that the permeate flux was affected both by the boundary layer resistance, which was reversible, and a membrane fouling part that was not reversible. The irreversible membrane fouling rate was not much affected by the feed flow rates at the lowest three levels, but was greatly decreased at the highest flow rate level, which indicates that for the used feed water solution, there was a threshold feed flow rate, above which membrane fouling was greatly reduced.

A two-stage RO unit with 8” diameter spiral wound elements operating on city tap water experienced after one week of operation a steadily increasing feed side pressure drop with time. Cleanings were required every 4-8 weeks to keep the pressure drop not to exceed the maximum allowed. The main problem was biofouling. All six elements in one of the housings in the first stage, and the first and last element in a housing in the second stage were taken out and tested individually. The feed side pressure drop at a constant feed flow rate was about 4.5 times the nominal one for the first three elements in the upstream housing, and then decreased for each element in the downstream direction to be less than

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1.5 times the nominal one for the last element in the second stage. The water permeability was 30 percent below nominal for the first element in the first stage, to increase with increasing position in the downstream direction, to reach the nominal water permeability for the first element in the second stage. During normal operation in the first stage housing, the feed flow superficial velocity decreased from about 0.2 m/s for the first element to about 0.1 m/s for the last element. The fouling rate was much higher for the first element than for the last element, despite double as high feed flow rate to the first one. Most likely, the high fouling rate for the first element was not caused by the initially higher permeate flux for this one, because later in operation, the permeate flux would be as high for the last element in the housing as for the first one. It is possible that the RO elements were very good at trapping the microbes, and the that formed biofilm was very good at catching the nutrients in the feed solutions, so it took a long time for the downstream elements to build up a thick biofilm.

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Membrane Fouling - UF & Water Treatment – 4

Tuesday July 15, 4:00 PM-4:30 PM, Honolulu/Kahuku

Exploiting Local Fouling Phenomena in Dead-End Hollow Fiber Filtration: The Partial Backwash Concept

W. van de Ven (Speaker), Membrane Technology Group, University of Twente, The Netherlands, [email protected] A. Zwijnenburg, Wetsus, centre for sustainable water technology, The Netherlands, [email protected] A. Kemperman, Membrane Technology Group, University of Twente, , The Netherlands, [email protected] M. Wessling, Membrane Technology Group, University of Twente, The Netherlands, [email protected]

Introduction Fouling of hollow fiber membranes during the filtration of natural organic matter (NOM) is a complex issue due to the largely unknown composition of the NOM. The particle size ranges from the nanometer to the micrometer scale and interaction with the membrane varies for the different NOM components. Due to the low axial flow that is present in a large part of the fiber in dead-end ultrafiltration, the fouling is not necessarily homogenous over the entire length of the fiber. In this work, we will discuss the axial distribution of fouling layers in hollow fiber ultrafiltration membranes and the application of a partial backwash concept, based on these results.

Local fouling phenomena We used two methods to assess the location of membrane fouling in dead-end ultrafiltration. The firts method visualized that the retention of a humic acid solution is significantly lower at the end of the module. In a second set of experiments, filtration performance was studied for individual modules by using five small modules in series. The results confirmed the visual observation that membrane fouling takes places mainly at the end of the module. Very high flux and retention (>95%) values are obtained in the initial part of the module, while very low retention (even negative retentions are possible) are found at the end of the module. The axial distribution is a result of the interplay between the low crossflow velocity, high diffusion of the humic matter, and the charge repulsion between the membrane and the matter.

The concept of partial backwashing The result of the experiments can be used to optimize hollow fiber filtration processes. We present the concept of partial backwashing. Instead of backwashing the complete module, only the part of the module that is fouled is backwashed, increasing the overall recovery of the process.

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Results The partial backwash concept was studied for humic acid solutions with and without the addition of calcium. The results show clearly that partial backwashing is as effective as conventional full module backwashing when no calcium is added, obtaining an 80% reduction in backwash water use. However, when calcium is added to the feed solution, partial backwashing is not successful. Addition of calcium leads to aggregation of the humic material, increasing NOM particle size and enhancing humic acid- membrane interactions. This leads to deposition of the material over the entire length of the fiber.

Conclusion Our work shows that the unique properties of hollow fiber dead-end filtration and feedwater can result in a fouling layer that is inhomogeneous over the length of the fiber. This is especially evident when particles are small and interaction with the membrane is low. When material deposits primarily at the end of the fiber, partial backwashing is an interesting way to reduce backwash water use.

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Membrane Fouling - UF & Water Treatment – 5

Tuesday July 15, 4:30 PM-5:00 PM, Honolulu/Kahuku

Fouling Resistant Coatings for Oil/Water Separation

Y. Wu (Speaker), University of Texas, Austin, Austin, Texas, USA –

B. McCloskey, University of Texas, Austin, Austin, Texas, USA V. Kusuma, University of Texas, Austin, Austin, Texas, USA H. Ju, University of Texas, Austin, Austin, Texas, USA H. Park, University of Ulsan, Korea B. Freeman, University of Texas, Austin, Austin, Texas, USA – [email protected]

The shortage of pure water is one of the world's most serious concerns. Consequently, water reuse and management is increasingly important. Produced water, often containing salts, heavy metals, emulsified oil and other organics, is the single largest waste stream in oil and gas production. If the organic content and salinity of produced water could be reduced to acceptable limits, produced water would represent a potential new water source with a wide variety of uses. Although membranes may be an effective tool for treating water from oil and gas production, membrane fouling is a serious problem that limits the efficiency of water purification.

The objective of this research was to find a method of preparing the thin-film composite membranes using N-vinyl-2-pyrrolidone crosslinked with N,N'-methylenebisacrylamide as the coating layer and an ultrafiltration membrane (i.e., polysulfone) as the support membrane to reduce fouling in oil/water emulsions. Three different prepolymerization compositions containing 50, 60 and 70 wt% water (labeled as 50H, 60H and 70H, respectively) and a fixed 85/15 ratio of NVP/MBAA were used as coating solutions. Thin-film composite membranes were successfully made, and their permeation and fouling properties were studied.

The thin-film composite membranes were characterized using several techniques. Fourier Transform Infrared Spectroscopy (FTIR-ATR) is a convenient tool for monitoring the conversion of the polymer coating solution and the existence of a coating layer. Based on ATR-FTIR studies of composite membranes, the coating layer is thin. Calculations based on the penetration depth of the infrared beam indicates that the coating layer is thinner than 1.2 micrometers. Scanning electron microscopy (SEM) was used to determine the existence and the thickness of coating layer, which was 1.3 ± 0.5 micrometers when using 50H as the coating solution and 0.2 ± 0.05 micrometers when 60H was used as the coating solution. However, for the 70H solution, the coating layer was too thin to be detected by SEM. As the water content in the

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prepolymerization mixture increases, the coating layer thickness decreases significantly.

To characterize their permeation and fouling properties, composite membranes were tested using oil/water emulsion crossflow filtration tests. After 24 hours permeation with oil/water emulsions used as model foulants, the uncoated PSF flux was down to 10 L/m2 hr, while thin-film composite membranes with 70H coating solution had a flux 8 times higher, demonstrating good oil fouling resistance. The oil rejection of thin-film composite membranes with all three coating solutions-50H, 60H and 70H-was as high as 99.5 %, and rejection remained constant, indicating that the PSF was thoroughly coated with the coating layer. From the pure water flux before and after the oil/water emulsion crossflow filtration test, the irreversible fouling index was calculated (i.e., permeance after oil water filtration divided by permeance before oil water filtration). 70H has a higher initial flux but a low irreversible fouling resistance; 50H exhibits lower initial flux but high irreversible fouling resistance. There is a trade-off between pure water flux and internal fouling in the thin-film composite membrane.

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Membrane Fouling - UF & Water Treatment – 6

Tuesday July 15, 5:00 PM-5:30 PM, Honolulu/Kahuku

On the Representativeness of Model Polymers in Fouling Research

A. Drews (Speaker), TU Berlin, Berlin, Germany - [email protected] A. Shammay, UNESCO Centre UNSW, Sydney, Australia V. Chen, UNESCO Centre UNSW, Sydney, Australia P. Le Clech, UNESCO Centre UNSW, Sydney, Australia

Objectives In an attempt to track down the culprit components or conditions, lab-scale fouling experiments where the complexity of the interacting phenomena is reduced are carried out by many groups all over the world. Such experiments often involve small-scale (test cell) membrane filtration experiments with either real feed suspensions, supernatants or model substances such as xanthan gum or alginate (e.g. [1]). In reducing the complexity, the representativeness of conclusions drawn from these trials becomes highly questionable - not only quantitatively but also qualitatively. During such investigations under allegedly more defined conditions a number of problems can be encountered, concerning both filtrations conditions (different fouling mechanisms occur at constant flux and constant pressure, respectively, or by lack of air scour in test cells [2]) and composition of the feed suspension. For the filtration of real feeds, it is known that even a few hours, which often elapse between sampling and filtration tests, can lead to potentially unrepresentative fouling behaviour [2]. Model polymers are assumed to be more stable - generally without proof - and more defined but might still be unrepresentative due to the following: a) The form in which they are obtained or prepared (completely dissolved or particulate) will affect their fouling/adsorption potential [3], b) the chemical structure of the substance might be largely different from that found in the real feed, c) the absence of the solids matrix might cause largely different fouling mechanisms, and d) fouling might not always mainly be caused by biopolymers. This study aims at elucidating the representativeness of model foulant experiments in fundamental fouling research.

Methods Test cell experiments (J = const, air-sparged, MF and UF membranes) were carried out with suspensions or solutions of alginate, xanthan gum, BSA, yeast, and bentonite (pure and spiked with BSA and/or alginate) under sub- and supercritical flux conditions. A new membrane was used for each trial. To determine the influence of “aging” of the model suspension on filtration results, experiments were repeated after several hours of stirring and pumping through the set-up. SMP, EPS and TOC were analysed in the feed and permeate [4, 5]. Results were compared to data obtained with sludge.

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Results It was found that not only feed protein, carbohydrate and TOC concentrations obviously differed strongly from those measured in sludge, but also that permeate concentrations generally were much higher than in sludge filtration. This indicates that polymer sizes or also fouling effects are quite different. TMP increase was also different for the investigated suspensions, however, irreversible fouling resistance could be correlated with TOC of the SMP for a number of suspensions indicating that TOC might a relevant measure of fouling. Regarding the aging effect, model foulant solutions were also subject to changes over time which can be due to continuous shear in pumps and in the vicinity of stirrers, temperature changes, or indeed even degradation. Initial TMP increase was reproducible but acceleration occurred up to 40% earlier after already 5 hours of feed conditioning. Temperature, which was deliberately allowed to rise over time (pumping power input) has an effect not only on viscosity but also on model substance properties like adsorption potential or ‘stickiness’ of the cake [6]. In a yeast + alginate suspension, especially carbohydrates and TOC decreased over time showing that potential foulants disappear or change during the course of successive trials.

Conclusions Results showed that like in sludge experiments, filterability and other properties of model suspensions can change over time. In order to be able to use model substances as defined foulants, fresh suspensions should be prepared regularly. Permeate concentration and rejection can give valuable information on the state of the solution. At the conference, more results will be presented on model-based analyses of data which yield more information on fouling mechanisms than permeability data in its raw form. Thus, improved protocols for model foulants experiments in fundamental research will be identified.

Acknowledgements Anja Drews gratefully acknowledges the financial support by the Deutsche Forschungsgemeinschaft (DFG DR763/2-1) and by the University of New South Wales.

References

[1] Ye Y, Le Clech P, Chen V, Fane AG, Jefferson B (2005) Desal 175, 7-20.

[2] Kraume M, Wedi D, Schaller J, Iversen V, Drews A (2008) Desal (in press).

[3] Nataraj S, Schomäcker R, Kraume M, Mishra IM, Drews A (2007) J Membr Sci 308 (2008), 152-161.

[4] Dubois M, Gilles KA, Hamilton JK, Rebers PA, Smith F (1956) Anal Chemistry 28, 350-356.

[5] Frolund B, Palmgren R, Keiding K. Nielsen PH (1996) Water Res, 1749-1758.

[6] Drews A, Mante J, Iversen V, Lesjean B, Vocks M, Kraume M (2007) Water Res 41, 3850-3858.

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Membrane Modeling II - Gas Separation – 1 – Keynote

Tuesday July 15, 2:15 PM-3:00 PM, O’ahu/Waialua

Modeling Approaches for the Design of High Performance Polymer Glassy Membranes for Small Gas Molecule Separations

P. Pullumbi (Speaker), Air Liquide, Jouy-en-Josas, France - [email protected] E. Tocci, Institute for Membrane Technology ITM-CNR, Rende (CS), Italy M. Heuchel, GKSS, Teltow, Germany S. Pelzer, GKSS, Teltow, Germay

The need to shorten the research cycle of novel materials used in gas separations technologies by coupling several computational approaches with experimental techniques has been the driving force for the recent developments in molecular modeling technology. Modeling of gas transport through polymer membranes is not straightforward because of the complexity of phenomena involved. In this study we propose a methodology composed out of several computational methods combining atomistic modelling of models of polymer membrane materials with Molecular Dynamics (MD) calculations as well as transition state theory (TST) simulation of transport properties of small gas molecules in these models followed by Quantitative Structure Activity Relationship (QSAR) analysis for the design of new polymer materials. The quality of the predicted transport properties of small gas molecules through membrane models strongly depends on the quality of these last ones. The large scatter often observed in simulated values of small gas molecule diffusion coefficient and solubility in the same glassy polymer membrane is related to the methodology applied for generating reproducible packing models of the membrane. In order to reduce this scatter, numerical analysis of structural features of the membrane model has been used for pre-selecting only the realistic ones for further use in simulations by means of transition state theory (TST) approach. In this study more than 200 polymer membrane packing models corresponding to more than 60 different polymers have been prepared. Simulated values via TST of Solubility and Diffusion coefficients for small gas molecules have been predicted for each packing model. Detailed Free Volume analysis has been carried out for each cell of the data set. A multi- level QSAR approach has been adopted in order to determine, first, the relevant descriptors (including information of free volume distribution and dynamics) and second, determine of the specific weight of each descriptor. Several “separated” QSAR studies (QSAR-monomers, QSAR-chain, QSAR- Cell) have been carried out and several descriptors have been selected for the composed study. The proposed computational methodology in this study whose validation is under progress, contributes to the joint experimental-theoretical efforts towards the rational design of membranes with improved properties.

The authors acknowledge the European Community for its partial support (Project: NMP3-CT-2005- 013644 MULTIMATDESIGN ).

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Membrane Modeling II - Gas Separation – 2

Tuesday July 15, 3:00 PM-3:30 PM, O’ahu/Waialua

Molecular Modeling of Free Volume in Poly (pyrrolone-imide) Copolymers

X. Wang (Speaker), University of California Berkeley, Berkeley, California, USA - [email protected] I. Sanchez, University of Texas at Austin, Austin, Texas, USA B. Freeman, University of Texas at Austin, Austin, Texas, USA

Poly (pyrrolone-imide) copolymers, ultra-rigid polymers which can mimic molecular sieves, have the potential to be used in the separation of olefin and paraffin gases in the petrochemical industry. The conventional separation of olefin and paraffin gases is done using energy intensive low temperature distillation. Using atomistic models, average cavity sizes and cavity size (free volume) distributions of poly (pyrrolone-imide) copolymers are calculated using the Cavity Energetic Sizing Algorithm (CESA). Cavity size distributions of poly (pyrrolone-imide) copolymers are consistent with the wide angle x-ray diffraction measurements.

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Membrane Modeling II - Gas Separation – 3 Tuesday July 15, 3:30 PM-4:00 PM, O’ahu/Waialua

Development of a Microscopic Free Volume Theory for Molecular Self-Diffusivity Prediction in Polymeric Systems

H. Ohashi (Speaker), The University of Tokyo, Tokyo, Japan - [email protected] T. Ito, Tokyo Institute of Technology, Tokyo, Japan T. Yamaguchi, Tokyo Institute of Technology, Tokyo, Japan

Molecular diffusivity in polymer matrices is an important dynamic physical property for membrane transports. Prediction of the diffusivity using some theoretical models is favorable, and thus, several diffusion models for polymeric systems have been proposed up to now. However, diffusivity prediction model without adjustable parameter has not been proposed yet because microscopic phenomena are not taken into account in the previous models.

Microscopically, molecular self-diffusion originates in the common mechanisms of molecular collisions and random walk motion in polymer systems as well as in simple liquids. Therefore, we developed a novel model for molecular diffusion in polymer by incorporating these two notions into the free volume theory. The free volume theory for polymeric systems contains two unknown parameters, so we introduced a newly developed concept, “shell-like free volume” around a molecule, and “random walk movement into neighbor free volume hole” into both of the unknown parameters. Incorporation of these microscopic concepts provides a predictive model, which can calculate self-diffusivity of mixing property using only pure component properties derived from experimental viscoelasticity and quantum chemical calculation.

Using this model, we can predict self-diffusivity of various molecules in polymer matrices without using any adjustable parameter. Our model can be applied to molecules having various shapes and molecular types of gas, solvent, and solute in several polymeric systems. The predictive ability of our model was found to be fairly acceptable in every case and thus, the model can be a useful tool for polymeric membrane designs.

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Membrane Modeling II - Gas Separation – 4

Tuesday July 15, 4:00 PM-4:30 PM, O’ahu/Waialua

A Molecular Pore Network Model for Nanoporous Materials

N. Rajabbeigi (Speaker), University of Southern California, California, USA - [email protected] B. Elyassi, University of Southern California, California, USA T. T. Tsotsis, University of Southern California, California, USA M. Sahimi, University of Southern California, California, USA

A new molecular pore network model for the structure of nanoporous materials, and in particular membranes, has been developed. The construction of the model starts with a three- dimensional (3D) box in which the atoms that constitute the material are distributed, either in crystalline form, or as an amorphous material which is obtained by annealing. The box is then tesselated using the Voronoi algorithm that partitions the space into irregular 3D polyhedra. A fraction of the polyhedra is then designated as the pores of the material, and all the atoms inside such polyhedra, as well as the dangling (singly-connected) atoms are removed. The size distribution of pore polyhedra can be tuned to match experimental data for the pore size distribution (PSD) of a given nanoporous material with any correlation function. Since the pore polyhedra are interconnected, the model takes into account the effect of the pore connectivity. Because the material is randomly tesselated and the dangling atoms are removed, the pores have rough internal surface, which is consistent with what is known experimentally. To test the model, we simulate adsorption isotherms for nitrogen, using equilibrium molecular dynamics simulations, in three silicon carbide (SiC) membranes by adjusting the average pore size of the model to the experimental data. Good agreement was obtained between the simulated and measured isotherms. The experimentally-validated model was then used for modeling transport of gaseous mixtures in the SiC membrane under a variety of conditions.

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Membrane Modeling II - Gas Separation – 5

Tuesday July 15, 4:30 PM-5:00 PM, O’ahu/Waialua

Modeling and Performance Assessment of Pd- and Pd/Alloy-based Catalytic Membrane Reactors for Hydrogen Production

M. Ayturk (Speaker), Worcester Polytechnic Institute, Worchester, Massachusetts, USA N. Kazantzis, Worcester Polytechnic Institute, Worchester, Massachusetts, USA Y. Ma, Worcester Polytechnic Institute, Worchester, Massachusetts, USA - [email protected]

As global competition for oil supplies steadily intensifies, transforming today’s oil dominated energy and transportation system to one running on hydrogen, represents one of the most daunting challenges. The production of hydrogen via natural gas steam reforming (MSR) and/or water-gas shift (WGS) reaction of the coal-derived syngas in Pd- and sulfur tolerant Pd/Alloy-based catalytic membrane reactors (CMRs) is an attractive technology which generates further interest primarily due to its great potential for process intensification. Motivated by the above considerations, the main objective of the present study is to develop a systematic and comprehensive modeling framework for the assessment of the impact of operating conditions on Pd-based CMR performance, as well as appropriately define indicators representing quantitative criteria for the attainment of key process intensification objectives (efficiencies in the use of material and energy resources, cost and “waste management” for a given production capacity target).

An isothermal mathematical steady-state model of an industrial size CMR for the MSR, WGS and methanation reactions was developed and a comparative performance assessment of the CMR versus a conventional packed bed reactor (PBR) was conducted. The temperature dependence of the reaction rate parameters, equilibrium and adsorption constants and the intrinsic reaction kinetics for the MSR and WGS reactions on a supported Ni catalyst were adopted from the detailed experimental study conducted by Xu and Froment. Based on the available literature data, an average hydrogen permeability for the pure-Pd films has been determined via linear regression analysis and used to estimate the rate of hydrogen removal in the CMR model. The Matlab® software was utilized to numerically integrate the set of process model equations via a 4th order Runga-Kutta algorithm. In particular, the model is structurally comprised of the requisite set of independent mass balance equations that describe the steady-state profiles of product distribution and total methane conversion along the lengths of both the tubular CMR as well as the PBR.

Validation of the CMR model was accomplished by simulating both the Pd-based CMR and the conventional PBR conditions reported in the literature. A detailed literature benchmarking showed that the models developed in this study

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predicted total methane conversion within 99% of the experimental values reported in the literature. The performance analysis was conducted by simulating the reactor model equations within a broad range of operating conditions, including reactor temperature, reaction- and permeate-side pressures, steam-to-methane ratio, membrane thickness, permeate-side sweep gas flow rate, effectiveness factor and bed porosity. In all simulation studies conducted, the Pd-based CMRs demonstrated superior performance over the traditional PBRs.

From a traditional process intensification perspective, CMRs exhibit considerable advantages over traditional reformers including the elimination of high and low temperature shift reactors, pre-Ox and hydrogen separator, thus enabling reaction, separation and product concentration processes to take place in a single unit operation. In order to develop a concrete quantitative performance evaluation framework for CMRs coupled with progress assessment towards the attainment of key process intensification objectives, a set of indicators are proposed that can be readily evaluated by simulating the aforementioned CMR model. In particular, the proposed reactor performance criteria and process intensification indicators are realized in terms of conversion, hydrogen recovery, membrane selectivity, reaction temperature and catalyst lifetime, process modularity, as well as energy and fuel savings and effective use of resources.

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Membrane Modeling II - Gas Separation – 6

Tuesday July 15, 5:00 PM-5:30 PM, O’ahu/Waialua

Free-Volume Holes in Amorphous Polymers for Solvent Diffusion: Reconsideration of the Free-Volume Theory By Equation-of-State, Group Contribution Method, PALS Measurement and Molecular Simulation

H. Lv (Speaker), Tsinghua University, China B. Wang, Tsinghua University, China - [email protected] J. Yang, Tsinghua University, China

In many processes such as gas separation, pervaporation and vapor permeation with a polymeric dense membrane, solvent diffusion behaviors in polymer matrix have attracted much attention, since the diffusivity is normally the rate- limiting step. Prediction of solvent diffusivity is of fundamental importance in the development of polymeric membrane design methodology for organic mixture separation [1-3]. In the past decades, the free-volume theory, which emphasizes the amount of free-volume vacancies as the dominant factor for diffusion, has served as the main basis for the correlation of diffusion behaviors in polymer-solvent systems. The model proposed by Vrentas and Duda is the representative of free-volume theory, in which most parameters can be obtained from pure component properties and no adjustable parameters are used [4-8]. However, free-volume parameters of polymer are usually determined by fitting the results from measurement of polymer viscoelasticity, meaning a great deal of time and cost consumption [9-11]. Moreover, the relationship between detailed information about the atomic-scale holes, which collectively constitute the free volume in polymers, and solvent transport properties still remains uncertainty. In order to remove these shortcomings, this study proposes four approaches to estimate polymer free volume and compare with the original model both theoretically and experimentally.

The first two approaches are equation-of-state (EOS) and group contribution method, both of which are based on macroscopic viewpoint of the free volume. For the former, the Simha-Somcynsky hole theory EOS is introduced into the free-volume theory; for the latter, the universal constant of the van der Waals volume of functional groups in polymer repeating units is introduced. Both of the modified models provide agreeable prediction of infinite dilution diffusion coefficients and solvent self-diffusion coefficients in several polymer- solvent systems without measuring polymer viscoelasticity. Furthermore, the individual predominance of these two approaches is discussed. In the EOS-modified model, the influence of pressure on solvent diffusivity in dilute polymer solutions can be included. In the group contribution-modified model, since all the parameters related to polymer can be determined only based on the knowledge of polymer structural units, a real process of membrane design with polymer

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functional groups becomes available. The third approach is positron annihilation lifetime spectroscopy (PALS) technique, which can measure the mean size and size distribution of subnanometer-size vacancies in polymers. The published mean hole volume detected by PALS is employed to predict solvent diffusion coefficients with the help of the EOS. The predictions are generally consistent with published diffusion data. In addition, the analysis of hole size distribution can prove the reliability of the EOS-approach and group contribution-approach. The fourth approach is molecular simulation, which can investigate free- volume holes from microscopic point of view. The simulation is performed on PVAc and PMA, which are structural isomers of each other. The quantitative relation between the simulation and the free volume defined by the Simha-Somcynsky EOS, PALS measurements and free-volume theory is given. The infinite dilution diffusion coefficients in PVAc are predicted using simulation method, and the predictions are in good agreement with experimental data.

This study provides a consistent feature to describe solvent transport in polymer matrix with both macro- and microscopic structure. The prediction ability of the original free-volume theory is improved by introducing the EOS and group contribution method. Therefore, the modified model is useful to understand mass transport in polymeric dense membranes and to develop a novel approach for membrane materials design.

Acknowledgement The authors gratefully acknowledge the financial assistance from the Major State Basic Research Development Program of China (973 Program) (No. 2003CB615701) and the National Natural Science Foundation of China (No. 20676068).

References

[1] Yamaguchi T, Miyazaki Y, Nakao SI, Tsuru T, Kimura S. Ind Eng Chem Res, 1998, 37, 177.

[2] Wang BG, Miyazaki Y, Yamaguchi T, Nakao SI. J Membr Sci, 2000, 164, 25.

[3] Wang BG. Membrane design for organic mixture separation [Ph.D. Dissertation]. University of Tokyo, Japan, 2000.

[4] Vrentas JS, Duda JL. J Polym Sci Polym Phys Ed, 1977, 15, 403.

[5] Zielinski JM, Duda JL. AIChE J, 1992, 38, 405.

[6] Hong SU. Ind Eng Chem Res, 1995, 34, 2536.

[7] Vrentas JS, Vrentas CM. Macromolecules, 1994, 27, 4684.

[8] Yamaguchi T, Wang BG, Matsuda E, Suzuki S, Nakao SI. J Polym Sci Polym Phys, 2003, 41, 1393.

[9] Lv HL, Wang BG. J Polym Sci Polym Phys, 2006, 44, 1000.

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[10] Wang BG, Lv HL, Yang JC. Chem Eng Sci, 2007, 62, 775.

[11] Lv HL, Wang BG, Yang JC. Polym J, 2007, 39, 1167.

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Membrane and Surface Modification I – 1 – Keynote

Tuesday July 15, 2:15 PM-3:00 PM, Wai’anae

New Chemically Modified Membranes in Bioseparations

D. Melzner (Presenting), Sartorius Stedim Biotech GmbH, Goettingen, Germany - [email protected] R. Faber, Sartorius Stedim Biotech GmbH, Goettingen, Germany

Chemically modified membranes are meanwhile widely used in bioseparations.

To obtain optimal separation results in specific process steps and to compete

The work has been done by identifying the critical membrane properties for an

New Membranes are presented, which fulfil optimal the needs for separation and

The results are discussed under consideration of the device construction and of

Examples of polishing of monoclonal antibodies solutions, virus removal and

Especially in the downstream processing of monoclonal antibodies and vaccinesthe membrane chromatography is established as an important unit operation.

with alternative techniques, intensive further development in optimization of themembrane properties and extension of available ligands is necessary.

optimal fit to the corresponding application and transfer of these results into theoptimal chemical structure.

purification of biomolecules like monoclonal antibodies or other proteins. The membrane structures in relation to the separation properties are discussed.

process design., because both have substantial influence on the performance the whole purification process.

virus harvesting are shown.

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Membrane and Surface Modification I – 2

Tuesday July 15, 3:00 PM-3:30 PM, Wai’anae

Surface-Initiated Atom Transfer Radical Polymerization: A New Tool to Produce High-Capacity Adsorptive Membranes

B. Bhut (Speaker), Clemson University, Clemson, South Carolina, USA S. Wickramasinghe, Colorado State University, Fort Collins, Colorado, USA S. Husson, Clemson University, Clemson, South Carolina, USA - [email protected]

When used as chromatography media, synthetic microporous or macroporous membranes offer advantages over resin-based media, such as low pressure drop, high production rate, and facile scale up and set up. In this presentation, we will describe how to surface modify commercially available regenerated cellulose membrane by atom transfer radical polymerization to produce high- capacity (>50 mg/ml) ion-exchange membranes for protein chromatography. The monomer 2- dimethylaminoethyl methacrylate was polymerized from cellulose membranes to convert them into weak anion-exchange membranes. Physicochemical properties of surface-modified membranes were studied as a function of polymerization time with various analytical measurement techniques that include scanning electron microscopy, atomic force microscopy, and attenuated total reflectance FTIR. Performance properties that were measured include buffer permeability and static protein adsorption capacities.

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Membrane and Surface Modification I – 3

Tuesday July 15, 3:30 PM-4:00 PM, Wai’anae

Gas and Liquid Permeation Studies on Modified Interfacial Composite Reverse Osmosis and Nanofiltration Membranes

J. Louie (Speaker), Stanford University, Palo Alto, California, USA - [email protected] I. Pinnau, Membrane Technology and Research, Inc., Menlo Park, California, USA M. Reinhard, Stanford University – Palo Alto, California, USA

Surface coating is a simple technique to modify water treatment membranes for enhanced fouling resistance. However, the conditions of the modification process and interactions between the membrane and the coating can impact membrane performance. A selection of reverse osmosis and nanofiltration membranes were coated with a thin water-permeable polyether-polyamide block copolymer layer (PEBAX 1657) to reduce the rate of fouling, and thereby increase cumulative flux. Improved fouling resistance was observed when treating an oil-water-surfactant emulsion with a PEBAX-coated seawater membrane, relative to an uncoated sample. However, pure-water flux values for some of the coated membrane types were lower than for uncoated membranes, and the reductions exceeded the predicted declines based on the series resistance model. Gas permeation tests were performed to assess how membrane modification procedures affect the separating layer morphology of thin-film composite reverse osmosis membranes. Selectivity data provided evidence for the presence of nanoscale separating layer defects in dry samples of six commercial membrane types. These defects were eliminated when the membrane surface was coated with a polyether-polyamide block copolymer (PEBAX 1657), as indicated by a 25-fold decrease in gas permeance and at least a two-fold increase in most selectivity values. Treatment with n-butanol reduced water flux and gas flux by 30% and 75%, respectively, suggesting that it negatively affects the membrane during the coating process. The results of this study demonstrate that gas permeation measurements can be used to detect morphological changes that impact membrane flux. It also demonstrates the need to evaluate incidental effects of modification procedures on membrane structure and performance.

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Membrane and Surface Modification I – 4

Tuesday July 15, 4:00 PM-4:30 PM, Wai’anae

Study of a Hydrophilic-Enhanced Ultrafiltration Membrane

T. Gullinkala (Speaker), University of Toledo, Toledo, Ohio, USA - [email protected] I. Escobar, University of Toledo, Toldeo, Ohio, USA

Different approaches of grafting poly (ethylene glycol) chains to commercially available cellulose acetate ultrafiltration membrane were considered and compared with respect to permeate flux, solute rejection and fouling prevention. Grafting was attained by forming reactive radicals on the membrane surface by using oxidation agent. Persulfate was used as the oxidizing agent due to its ease of use in aqueous phase. Formation of free radicals was confirmed by their reaction with sulfate ions and consecutive sulfur mapping images. Low molecular weight PEG chains were attached to the membrane surface through the reaction with these free radicals. Low molecular weight PEG was chosen to reduce the chance of cross linking on the membrane surface. The propagating PEG chains were capped by a chain transfer agent after optimum reaction time. Chain termination was achieved by the chain transfer agent. The function of chain transfer agent was established by SEM mapping.

Optimum reaction times for the modification were 10 minutes for oxidizing agent, 5 minutes for the monomer and 2.5 minutes for the chain transfer agent. These contact times were used in the two different approaches used to perform the modification. In one method, called bulk method membrane samples were immersed in the liquid reagents associated with vigorous stirring. Samples were dissolved first in oxidizing agent then in aqueous PEG solution and finally in chain transfer agent for the above mentioned reaction times. In another method called drop method, a membrane sample was placed flat on a glass sample holder and solutions containing the oxidizing agent were added to the membrane sheet drop wise so that the entire sample sheet was filled with the persulfate solution. After ten minutes the oxidizing solution was replaced by PEG solution for chain propagation and then chain transfer agent was added drop wise for controlling chain length. Modification was confirmed by FTIR spectra and SEM mapping.

Two different feed solutions were used to characterize the modification. Dextran solution was used to determine the effect of modification on uncharged particulate matter and modeled sea water to determine the influence of graft polymerization on natural organic matter during filtration through cellulose acetate membranes. In these experiments sea water was simulated by forming an aqueous solution composed of 2 mg/l of each Suwannee River Fulvic and Humic Acids, along with 0.1 mM CaCl2 as a representative of divalent cations,

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0.1 mM NaHCO3 as buffer system,1M NaCl as background electrolyte and 1 mg/l of SiO2.

Drop method modification of the membrane resulted in better flux than bulk modified and virgin membranes during ultrafiltration of dextran solution. It also resulted in 10% increase in the rejection capacity than that of virgin membrane. Drop modification of membrane also led to modest decrease in the roughness of the membrane which reduces the membrane susceptibility to fouling. Only bulk modification was used to polymerize the membranes in the case of ultrafiltration of modeled sea water for the ease of use. Different sets of filtration runs were performed such as 1 minute, 5 minutes, 15 minutes and up to 6 hours to determine the fouling patterns due to natural organic matter such as humic and fulvic acids present in the feed solution. In this case modification led to the increase in the permeability of the membrane and finer fouling patterns during filtratuion.

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Membrane and Surface Modification I – 5

Tuesday July 15, 4:30 PM-5:00 PM, Wai’anae

Crosslinked Poly(ethylene oxide) Fouling Resistant Coating Materials: Synthesis, Characterization, and Application

H. Ju (Presenting), University of Texas at Austin, Austin, Texas, USA B. McCloskey, University of Texas at Austin , Austin, Texas, USA A. Sagle, University of Texas at Austin , Austin, Texas, USA B. Freeman, University of Texas at Austin, Austin, Texas, USA – [email protected]

Various crosslinked poly(ethylene glycol) diacrylate (XLPEGDA) materials were synthesized via free-radical photopolymerization of poly(ethylene glycol) diacrylate (PEGDA) solutions. These materials have potential as fouling-resistant coatings for commercial ultrafiltration (UF) membranes. PEGDA chain length (n=10~45) and water content in the prepolymerization mixture (0~80 wt.%) were varied in synthesizing the XLPEGDA materials, and their water transport ability and solute sieving properties were characterized. Water permeability increased with increasing water content in the prepolymerization mixture and with increasing PEGDA chain length. However, solute rejection decreased with increasing prepolymerization water content or PEGDA chain length. Finally, the fouling resistance of XLPEGDA materials was evaluated with static protein adhesion experiments, and less BSA accumulated onto XLPEGDA surfaces when the film was prepared at higher prepolymerization water content or using longer PEGDA chains. When XLPEGDA materials were applied to polysulfone (PSF) UF membranes to form coatings on the surface of the PSF membranes, the coated PSF membranes had water flux values 400% higher than that of an uncoated PSF membrane after 24 hours of operation, and the coated membranes had higher organic rejection than the uncoated membranes in oil/water crossflow filtration experiments.

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Membrane and Surface Modification I – 6

Tuesday July 15, 5:00 PM-5:30 PM, Wai’anae

Dopamine: Biofouling-Inspired Anti-Fouling Coatings for Water Purification Membranes

B. McCloskey (Speaker), The University of Texas at Austin, Austin, Texas, USA H. Park, University of Ulsan, Korea B. Freeman, The University of Texas at Austin, Austin, Texas, USA – [email protected]

One of the main issues facing water purification membrane technology is membrane fouling, which is the deposition of organic contaminants on the membrane surface or in its pore structure. Fouling leads to a catastrophic decrease in water flux which, in turn, results in high operating costs and short membrane lifetime. Many methods have been studied to combat membrane fouling, most of which focus on two general techniques: introducing high fluid shear on the feed stream side, such as backpulsing, dean vortices, and air sparging, and altering the surface properties of the membranes, either through surface grafting/coating, plasma treatment, or other chemical modifications. Although feed flow instabilities increase flux in some MF and UF membrane applications, fouling is still a concern. Furthermore, combining surface modified membranes with increased surface shear will lead to higher membrane efficiency over using one of the two techniques. Therefore, this study focuses on producing a simple chemical modification technique that uses a strongly bound, hydrophilic ad-layer, which is stable under even the most extreme fluid shear environments.

Dopamine has been recently used to mimic a mussel�s adhesive plaque. In alkaline solutions, dopamine will self-polymerize (polydopamine) and deposit on virtually any surface with which it comes into contact. By using this simple deposition technique, polydopamine is “coated” onto polysulfone (PSf) ultrafiltration (UF) membranes and polyamide (PA) reverse osmosis (RO) membranes. Polydopamine was found to increase a membrane�s surface hydrophilicity and therefore increase its resistance to fouling. After one day of oil-emulsion fouling, the polydopamine-coated PSf membrane showed a flux over 8 times higher than that of the unmodified PSf membrane, and a polydopamine-modified PA RO membrane exhibited a 30% flux increase over the unmodified membrane. Furthermore, organic rejection of the modified membranes is similar to that of the unmodified membranes.

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Oral Presentation Abstracts

Morning Session

Wednesday, July 16, 2008

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Plenary Lecture II Wednesday July 16, 8:00 AM-9:00 AM, Hawai’i Ballroom

Thermally Rearranged Polymer Membranes With Cavities Tuned for Fast Transport of Small Molecules Professor Young Moo Lee, Hanyang University, Seoul, Korea - [email protected]

We demonstrate that polymers with an intermediate cavity size, a narrow cavity size distribution and a shape reminiscent of bottlenecks connecting adjacent chambers, such as those found elegantly in Nature in the form of ion channels and aquaporins, yield both high permeability and high selectivity [1]. Central to our approach for preparing these intermediate sized cavities is controlled free volume element formation via spatial rearrangement of the rigid polymer chain segments in the glassy phase. It is known that a rearrangement, such as intramolecular cyclization, in glassy polymers could lead to changes in polymer structure for gas transport [2]. For this purpose, aromatic polymers interconnected with heterocyclic rings (e.g., benzoxazole, benzithiazole, polypyrrolone and benzimidazole) are of interest because phenylene-heterocyclic ring units in such materials have a flat, rigid-rod structure with high torsional energy barriers to rotation between two rings [3]. The stiff, rigid ring units in such flat topologies pack efficiently, leaving very small penetrant-accessible free volume elements. This tight packing is also promoted by intersegmental interactions such as charge transfer complexes between heteroatoms containing lone electron pairs (e.g., O, S and N). The genesis of these materials was the demand for highly thermally and chemically stable polymers. However, their application as gas separation membranes was frustrated by their lack of solubility in common solvents, which effectively prevents them from being prepared as thin membranes by solvent casting, which is the most widely practiced method for membrane preparation. Most of all, the greatest benefit of these Thermally Rearranged (TR) polymers is the ability to tune the cavity size and distribution for specific gas applications including CO2 from flue gas by using various templating molecules and heat treatments, using one starting material. References 1. H.B. Park, C.H. Jung, Y.M. Lee, A.J. Hill, S.J. Pas, S.T. Mudie, E. Van Wagner, B.D. Freeeamn, D.J. Cookson, Science 318, 214 (2007). 2. I.K. Meier, M. Langsam, H.C. Klotz, J. Membr. Sci. 94, 195 (1994). 3. V.J. Vasudevan, J.E. McGrath, Macromolecules 29, 637 (1996).

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Gas Separation III – 1 – Keynote

Wednesday July 16, 9:30 AM-10:15 AM, Kaua’i

Membrane Engineering Progresses and Potentialities in Gas Separations

E. Drioli (Speaker), Research Institute on Membrane Technology, ITM-CNR, Italy - [email protected]

Membrane processes for gaseous mixture separations are today a well consolidated technique competitive in various cases with the traditional operations [1]. Separation of air components, natural gas dehumidification, separation and recovery of CO2 from biogas and natural gas, and of H2 from refinery industrial gases are some examples in which membrane technology is applied already at industrial level. The separation of air components or oxygen enrichment has advanced substantially during the past 10 years. The oxygen- enriched air produced by membranes has been used in various fields, including chemical and related industries, the medical field, food packaging, etc. The possibility of utilizing membrane technology in solving problems such as the greenhouse effect related to CO2 production has also been suggested. Membranes able to remove CO2from air, having a high CO2/N2 selectivity, might be used at any large-scale industrial CO2source as power station in petrochemical plants. The CO2separated might be converted by reacting it with H2 in methanol, starting a C1 chemistry cycle. A membrane reactor might be ideally used to carry out hydrogenation reactions for chemical production using CO2 recovered from exhaust gases by membrane separation. The separation and recovery of organic solvents from gas streams is also rapidly growing at the industrial level. Polymeric rubbery membranes that selectively permeate organic compounds (VOC) from air or nitrogen have been used. Such systems typically achieve greater than 99% removal of VOC from the feed gas and reduce the VOC content of the stream to 100 ppm or less. The significant positive results reached in gas separation membrane systems are however still far away to realize the potentialities of this technology. Problems related to the pretreatments of the streams, to the membranes life time, to their selectivity and permeability still exist slowing down the growth of large scale industrial applications. New polymeric inorganic and hybrid materials are under investigation in different laboratories around the world. The possibility to realize also new mass transport mechanisms as the ones characterizing the perovskites membranes is becoming of interest. The case of O2 and H2 transport in these membranes might be extended to other species by realizing new specific materials. Molecular dynamics studies, fast growing in this area, might contribute to the design of these new inorganic materials or to the appropriate functionalization of existing polymeric membranes. Amorphous perfluoropolymers might be utilized for casting asymmetric composite membranes [2] with interesting selectivity and permeabilities for various low molecular species. Their cost is however a

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negative aspect. With the introduction of process intensification strategy also in to the petrochemical industry, a large new areas will be open for gas separation membrane systems. The possibility to realize integrated membrane operations in the ethylene process, for example, has been studied and is under investigations [3]. Some of the drawbacks of the membrane operations such as the necessity of accurate pre- treatments, might be solved by combining, as already done in water treatments, various membrane operations in the same industrial process. The recent studies on carbon nanotubes with the unexpected very high permeability and selectivities, the progresses in zeolite membranes and in hybrid membranes where polymers and specific absorbers are combined, are offering interesting new opportunities for making membrane operations dominant also in gas separations and gas conversions.

References

[1] Drioli, E: Gas Separation Membranes: A Potential Dominant Technology. Special Issue. Trends in Gas Separation Membranes. (Membrane) 31, (2), 000- 000 (2006)

[2] Baker RW, Wijmans JG, Kaschemekat JH: ’The Design of Membrane Vapor-Gas Separation Systems’, Journal of Membrane Science, , 55-62 (1998)

[3] Bernardo P, Criscuoli A, Clarizia G, Barbieri G, Drioli E, Fleres G, Picciotti M : Applications of membrane unit operations in Ethylene Process, Clean Technologies and Environmental Policy, 6, (2) 78 (2004)

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Gas Separation III – 2

Wednesday July 16, 10:15 AM-10:45 AM, Kaua’i

Evolution of Natural Gas Treatment with Membrane Systems

L. White (Speaker), W.R. Grace & Co.-Conn., Littleton, Colorado, USA - [email protected] C. Wildemuth, Grace Davison Membranes, Littleton, Colorado, USA

Membrane treatment of natural gas to produce pipeline quality feedstock was commercially introduced in the early 1970’s. Cellulose acetates (CA) were found to be the polymer of choice for these early systems. Polyimides were identified by the 1980;s as a next generation polymer for natural gas treatment. But despite the remarkable properties exhibited by the polyimides the CA based systems are today still competitive in real world separations.

Remaining of key interest are the effects of impurities in the natural gas stream on the membranes. Interactions with condensable hydrocarbons are different between CA and polyimide membranes.

Since these technologies continue to improve, this paper will explore some of the key aspects in the evolution of membrane performance, packaging, and engineering of large-scale systems for natural gas processing. Will current trends toward large-scale installations be maintained in the future?

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Gas Separation III – 3

Wednesday July 16, 10:45 AM-11:15 AM, Kaua’i

CO2 Permeation With Pebax-Based Membranes for Global Warming Reduction

Q. Nguyen (Speaker), Rouen University, France - [email protected] J. Sublet, Rouen University, France D. Langevin, CNRS, France C. Chappey, CNRS, France J. Valleton, CNRS, France P. Schaetzel, CAEN University, France

Carbon dioxide extraction from nitrogen- rich gas streams produced by fossil- fuel- based power plants is of growing interest, both within industry and government, for the gas sequestration in a global warming reduction strategy. The classical gas- scrubbing process is energy- voracious and source of extra- pollution due to the need of regeneration of amines, the absorbent. Membrane processes may offer attractive alternatives to reduce the emission of this greenhouse effect source, due to their well-known advantages from the environmental and energetic viewpoints. The success of a gas permeation process relies on the possibility of obtaining membranes with high- performances and good mechanical/ thermal stabilities. Composite membranes consisting of an asymmetric glassy membrane whose surface defects are sealed with a thin polymer layer are generally the preferred structure, because of their technological feasibility. Sofar, such a concept of composite membranes with a gutter silicone layer has been successfully used for separation membranes e.g. for the hydrogen recovery or oxygen/ nitrogen production from air. The performances of the composite membranes depend critically on the gas nature and on the intrinsic properties of the composite layers. Contrary to hydrogen and other gases of very low normal boiling points, CO2 is a polar gas of similar molecular size to nitrogen, that can significantly interacts with certain chemical groups. We followed Lin and Freeman's approach* in developing new polymer materials for the membrane selective layer. The approach consists of selecting polymers of high CO2 solubility and CO2/light gas solubility selectivity by introducing polar groups in polymers. Ether oxygens in polyethylene oxide (PEO) appeared to be the most useful groups*. Commercial Pebax® copolymer containing "soft" PEO /PTMO and "hard" polyamide (6 or 12) blocks were chosen as the base polymers in this study because the compromise they provide between a high content of PEO and good mechanical properties. Membranes made of extruded and solvent- cast Pebax® block copolymers of different structures were studied by gas permeation, DSC and AFM. The change in the transport characteristics with the Pebax®- type appeared to be complex, due to multiphase structure of the materials: EO content is not the sole factor that controls the membrane performances. The best Pebax® material for CO2/N2

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separation was next blended with different ethylene oxide- containing polymers and studied in gas permeation. In general, the CO2/N2 separation performances of the blends were depressed by blending, except for the blend with liquid polyethylene glycol (PEG) of low molecular weight. For the latter blend, both the permeability and the selectivity were improved, probably due to the high mobility of the PEG chain and absence of its crystallinity. Such materials, which derive from commercially available products, can be easily combined with a microporous support to yield a composite membrane for the CO2 abatement.

*Haiqing Lin and Benny D. Freeman, Materials selection guidelines for membranes that remove CO2 from gas mixtures J. Molec. Struct., 739 (2005) 57-74

Q. T. Nguyen, J. Sublet, D. Langevin, C. Chappey, J. M. Valleton and P. Schaetzel*, UMR 6522, CNRS- Rouen University, 76821 Mont St Aignan Cedex- France * Laboratoiry of material processes, Caen University, 14032 Caen Cedex- France Corresponding author: trong.nguyen@univ- rouen.fr

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Gas Separation III – 4 Wednesday July 16, 11:15 AM-11:45 AM, Kaua’i

A Membrane Process to Capture CO2 from Power Plant Flue Gas

T. Merkel (Speaker), Membrane Technology and Research, Menlo Park, California, USA - [email protected] H. Lin, MTR, Menlo Park, California, USA S. Thompson, MTR, Menlo Park, California, USA R. Daniels, MTR, Menlo Park, California, USA A. Serbanescu, MTR, Menlo Park, California, USA R. Baker, MTR, Menlo Park, California, USA

The use of coal as fuel to make power inevitably produces carbon dioxide (CO2) as a byproduct. In the future, this CO2 must be captured and sequestrated. A number of technologies are being evaluated for CO2 capture. Membrane technology is an attractive approach because of its inherent advantages such as high energy efficiency, a small footprint, environmentally friendly operation (no chemicals), mechanical simplicity, and good reliability.

We have developed new CO2 selective membranes and process designs to recover CO2 from power plant flue gas. These membranes have CO2 permeances 10 times higher than conventional commercial membranes combined with high CO2/N2 selectivities. Bench scale test results on the membrane and modules will be discussed. Sensitivity studies will illustrate the optimal membrane properties for this application. System designs and simulations for a 500 MWe power plant will be shown to illustrate the effect of operating conditions (such as required CO2 recovery) on the cost of CO2 capture. Based on the best system design developed, achieving 90% CO2 recovery requires 18% of the power produced by the power plant.

In general, removal of CO2 from coal power flue gas is technically feasible with current membranes, but remains economically challenging. Higher flux membranes and low-cost ways of packaging them in large modules will improve the competitiveness of this separation approach. Also key to further development of this technology will be collaboration of membrane system producers and coal power plant designers.

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Gas Separation III – 5

Wednesday July 16, 11:45 AM-12:15 PM, Kaua’i

Membranes and Post Combustion Carbon Dioxide Capture: Challenges & Prospects.

E. Favre (Speaker), LSGC CNRS, Nancy, France - [email protected]

CCS (Carbon Capture & Sequestration) is a key issue in the reduction of greenhouse gases emissions. The capture step, which corresponds to the most expensive part of the technological chain, can be potentially achieved thanks to different processes. Numerous strategies are currently explored in order to identify the most efficient and less expensive process, which could reach a high CO2 capture ratio (typically 80 % or more), together with the production of a carbon dioxide stream of high purity (typically a volume fraction of 0.8 or more) [1]. From the energy requirement point of view, the EU has fixed 2 GJ per ton of carbon dioxide captured as a target [2]. Surprisingly, gas separation membranes are often discarded for this application [3].

This presentation intends to give an overview of the different strategies which can be proposed in order to use gas separation membranes for post combustion carbon capture in an industrial context (e.g. power plants, steel or cement manufacturing).

In a first step, challenges for membrane materials will be analysed. The major targets of the capture process in terms of selectivity, energy requirement and productivity will be reviewed and compared to membrane performances (permeability / selectivity / permeance). An up to date review of the various membrane materials which could potentially be proposed (polymers, mineral membranes, mixed matrix membranes, fixed site carrier membranes, liquid membranes) will be critically discussed according to these requirements.

In a second step, novel process strategies will be proposed, in order to minimize the energy requirement. Reverse selective materials, pressurised combustion, water entrainment and concentrated CO2 post combustion streams will be briefly exposed. A novel hybrid process will be more specifically detailed [4]. The key concept is based on the minimal work of concentration. A capture framework which combines an oxygen enrichment step before combustion and a CO2 capture step from flue gas has been investigated. The potentialities of this hybrid process from the energy requirement point of view are discussed. It is shown that the hybrid process can lead to a 35% decrease of the energy requirement (expressed in GJ per ton or recovered CO2) compared to the standard capture technology (i.e. oxycombustion), providing that optimal operating conditions are chosen. These promising performances can be achieved with a membrane

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selectivity of 50 or more, which is realistic for the CO2/N2 mixture. Applications of this concept to biogas power plants appear to be extremely attractive.

[1] Davidson, O., Metz, B. (2005) Special Report on Carbon Dioxide Capture and Storage, International Panel on Climate Change , Geneva, Switzerland, (www. ipcc.ch).

[2] Deschamps P., Pilavachi, P.A. (2004) Research and development actions to reduce CO2 emissions within the European Union. Oil & Gas Science and Technology 59 (3) : 323-33

[3] Favre, E. (2007) Carbon dioxide recovery from post combustion processes: Can gas permeation membranes compete with absorption? Journal of Membrane Science, 294, 50-59.

[4] Favre, E., Bounaceur, R., Roizard, D. (2008) A hybrid process combining enriched oxygen combustion and membrane separation for carbon dioxide post combustion capture. International Journal of Greenhouse Gas Control, submitted

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Gas Separation III – 6

Wednesday July 16, 12:15 PM-12:45 PM, Kaua’i

The Effect of Sweep Uniformity on Gas Dehydration Modules

P. Hao (Speaker), The University of Toledo, Toledo, Ohio, USA G. Lipscomb, The University of Toledo, Toledo, Ohio, USA - [email protected]

Air dehydration membranes offer a simple, cost effective solution to humidity control. Membrane units may be installed in-line and require no- auxiliary utilities - only a portion of the feed gas is lost and a small pressure drop is incurred.

To produce desired dew points, a portion of the product gas typically is used as sweep in the module. Sweep lowers the water concentration in the permeate to permit sufficient reduction of the water concentration in the retentate (non- permeate) stream.

The literature reports numerous ways to create the sweep stream including: 1) making the fibers non-selective at the product end, 2) introducing the sweep from an external collar around the module, and 3) inserting tubes through the tubesheet that allow communication between the product header and the shell of the module.

We report simulations of the sweep distribution within the shell and its effect on module performance. Two types of simulations are considered: 1) simulations that explicitly predict flow fields within the shell based on how the sweep gas is introduced and 2) simulations that assume the sweep flow around each fiber is distributed in a Gaussian manner.

The use of fibers that are non-selective at the product end is most efficient based on module capacity and dry gas recovery. Introducing the sweep through an external collar or internal tubes is poorer due to poorer gas distribution in the shell.

Predictions based on explicit calculation of shell flow fields are in good agreement with those based on a Gaussian sweep distribution using a standard deviation in sweep flow equal to ~15% of the average sweep flow rate. We believe the results of this work may be used to evaluate alternative methods providing sweep in a module.

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Drinking and Wastewater Applications III – 1 – Keynote

Wednesday July 16, 9:30 AM-10:15 AM, Maui

Membranes and Water: the Role of Hybrid Processes

A. Fane (Speaker), Director, Singapore Membrane Technology Centre, NTU, Singapore - [email protected]

Membrane technology now has a major role in water and wastewater treatment. In many cases the membrane does not operate alone but is coupled with other unit operations, giving us Hybrid Membrane Processes. Further, in the majority of cases the membrane process is low pressure microfiltration or ultrafiltration and the hybrid component allows greater removals to be achieved. Submerged membrane systems provide a simple concept with the ‘unit operation’ in the tank and the membranes providing both inventory control and separation.

This presentation discusses a number of hybrid processes including adsorption, photocatalysis [1] and combined adsorption and photocatalysis for water treatment. In these examples the membrane plays an inventory management role but provides little solute separation; typically fouling is a minor concern. For wastewater treatment the submerged MBR is the dominant hybrid and fouling is the dominant issue. The MBR fouling ‘roadmap’ [2] is revisited with an eye on recent developments. In the MBR the membrane may provide partial ‘solute’ removal as well as complete particle removal. Finally a novel MBR [3] involving membrane distillation provides an approach to complete solute retention of solutes. The challenges faced by the MDBR concept are outlined.

[1] S. S. Chin, T. M. Lim, K. Chiang and A. G. Fane, Factors affecting the performance of a low-pressure submerged membrane photocatalytic reactor., Chem Eng J., 131 (2007) 53-63.

[2] J. Zhang, H. C. Chua, J. Zhou and A. G. Fane, Factors affecting the membrane performance in submerged membrane bioreactors, Journal of Membrane Science, 284 (2006) 54-66.

[3] A. G. Fane, J. Phattaranawik and F. S. Wong, Contaminated inflow treatment with membrane distillation bioreactor, PCT/SG2006/000165 Filing date 16 June 2006 (2006).

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Drinking and Wastewater Applications III – 2

Wednesday July 16, 10:15 AM-10:45 AM, Maui

Coagulation-Ceramic Microfiltration Hybrid System Effectively Removes Virus that is Difficult to Remove in Conventional Coagulation-Sedimentation-Sand Filtration Process

N. Shirasaki, Hokkaido University, Sapporo, Japan T. Matsushita (Speaker), Hokkaido University, Sapporo, Japan - [email protected] Y. Matsui, Hokkaido University, Sapporo, Japan M. Kobuke, Hokkaido University, Sapporo, Japan T. Urasaki, Hokkaido University, Sapporo, Japan K. Ohno, Hokkaido University, Sapporo, Japan

INTRODUCTION Ceramic membranes have attracted attention in the field of drinking water treatment in Japan. However, in general, ceramic membranes are microfiltration (MF) devices, so their pore sizes are not small enough to exclude particles with diameters less than tens of nanometers. Included among such small particles are some of the pathogenic waterborne viruses. These viruses cannot be excluded by ceramic membranes alone. To compensate for this disadvantage, it was proposed that coagulation, which is usually employed to destabilize and aggregate small particles and then to remove them under gravity, be used in combination with ceramic MF. Our group has already reported the usefulness of the coagulation- ceramic MF hybrid system for virus removal. However, evaluation of treatment processes in terms of virus removal is generally based on virus concentration quantified by plaque forming unit (PFU) method; our previous report also evaluated the hybrid system by the method. Judging from its measurement principle, the PFU method detects infectious virus alone, but does not detect inactivated one. Therefore, quantification of virus in the MF permeate by the PFU method might underestimate the potential risk of virus, because a part of the virus is inactivated during the treatment process. If the temporarily inactivated virus recovers its infectivity after the process, it might pollute our drinking water. In this meaning, investigating removal of virus including inactivated one as well as infectious one is very important for the evaluation of treatment processes. Accordingly, the objectives of the present study are to investigate the removal of virus regardless of its infectivity by using polymerase chain reaction (PCR) method, and to compare the removals during the coagulation-ceramic MF hybrid system and the conventional coagulation-sedimentation-sand filtration process for confirming superiority of the hybrid MF system in virus removal.

MATERIALS AND METHODS (1) Virus used Bacteriophage MS2, whose diameter is 23 nm, was used as a model virus. Virus was quantified by both the PFU and PCR methods. The PFU method quantifies infectious virus, while the PCR method quantifies total virus particles regardless of their infectivity.

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(2) Coagulation-sedimentation-sand filtration tests Virus was added to river water at around 108 pfu/mL. PACl (polyaluminum chloride, 1.08 mg- Al/L) was injected to the water as a coagulant. The water was stirred rapidly for 2 min, slowly for 28 min, and then left at rest for 20 min, allowing the generated floc to settle down. After settling, the supernatant was pumped into a small column with an infill of silica sand at a constant flow rate (5000 LMH).

(3) Coagulation-ceramic MF hybrid system The river water was spiked with virus at around 10^8 pfu/mL. The river water was pumped into the system at a constant flow rate (83 LMH). After PACl was injected to the water at 1.08 mg-Al/L, the water was fed into the ceramic MF module (pore size: 100 nm) in dead-end mode.

RESULTS AND DISCUSSION (1) Virus removal during conventional process Removal of infectious virus was 3.6 log, indicating that a certain level of removal of infectious virus was achieved during the conventional process. In contrast, removal of virus particles was only 2.1 log, which is smaller than that of infectious virus. In other words, over 30 times more virus particles were leaked from the process than the value expected from the result obtained by the PFU method. Although most of the virus particles which were just eluted from the sand column lost their infectivity (97%), they might recover their infectivity after the process. In this meaning, the conventional process does not ensure the high-efficient removal of virus.

(2) Virus removal during coagulation-ceramic MF hybrid system The hybrid MF system successfully removed infectious virus: the removal was 4 to 6 log. This value was higher than that in the conventional process, because the microfloc, which enmeshed virus particles, was not removed by the conventional process owing to its small size, but was removed by the hybrid MF process. The hybrid MF system also achieved high removal of virus particles: the removal was 4-5 log, which is more than 2 log higher than that by the conventional process. In this way, high removal was achieved by the hybrid MF system not only for infectious virus but also for virus particles including inactivated virus.

CONCLUSION (1) Although relatively high removal of infectious virus was achieved by the conventional treatment process (3.6 log), the removal of virus particles was only 2.1 log. Inactivated virus particles were leaked from the process. (2) In contrast, coagulation-ceramic MF hybrid system successfully removed virus particles regardless of their infectivity: 4-5 log for infectious virus and 4-6 log for virus particles. Superiority in virus removal of the hybrid MF system was demonstrated.

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Drinking and Wastewater Applications III – 3

Wednesday July 16, 10:45 AM-11:15 AM, Maui

Membrane Enhanced Ultraviolet Oxidation of Polyethylene Glycol Wastewaters

D. Patterson (Speaker), Laboratory for Green Process Engineering, University of Auckland, Auckland, New Zealand - [email protected] T. Vranjes, Laboratory for Green Process Engineering, University of Auckland, Auckland, New Zealand

Ultraviolet (UV) advanced oxidation is a commonly used system used to degrade biologically recalcitrant wastewaters. It typically consists of a non selective flow- through reactor containing ultraviolet lamps irradiating a wastewater, into which an oxidant is dosed. The UV energy is sufficient to generate the strongly oxidising hydroxyl free radical (HO") from the water and oxidant, which mineralises the organic compounds in the wastewater via a series of radical reactions. Standard UV oxidation systems do not give an efficient treatment, as they can be non- selective and wasteful of the oxidant and other active radicals because they have no method of ensuring that only fully oxidised compounds leave in the effluent. This can have dire consequences: If the oxidation technology is the sole means of treating the water, untreated waste may exit the system, contravening the discharge consent. If the water is being pre- treated by the oxidation technology to make it more biodegradable, then the more refractory compounds may not be adequately oxidised, leaving them biologically recalcitrant. Finally, the radicals (which destroy the organic waste) are always lost with the treated effluent, creating a severe process inefficiency.

A new technology, called Membrane Enhanced Oxidation (MemOx), could overcome these limitations. If the compounds in the water streams undergo an order of magnitude change in size when oxidised, ionize, or change polarity, then a membrane may be applied to selectively retain the unoxidised molecules in the UV reactor. The membrane is chosen so that unoxidised molecules cannot permeate through the membrane, whilst the smaller, sufficiently oxidised molecules permeate and are discharged in the effluent. Also, by recycling partially oxidised molecules back into the reactor, this technology can increase the rate of reaction by synergistic rate acceleration. This is because the recycled, unoxidised effluent contains radical species, which increase the radical concentration in the reactor, thereby increasing the rate of reaction.

This paper will outline the preliminary work conducted at the University of Auckland developing the MemOx process. PEG1500 was chosen as the model organic pollutant and UV oxidised using solutions at 1 to 2 g/L using hydrogen peroxide (at varying concentrations) as the oxidant. The oxidation was carried

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out with UV light supplied by a 254nm low pressure mercury lamp. All membrane filtration experiments were conducted using a dead-end stainless steel cell with an effective membrane area of 13.9 cm2 pressurised by nitrogen gas at 3000 kPa. A Filmtec nanofiltration membrane was used in all tests. Dead-end cell rejection tests showed that that the Filmtec membrane was able to give a rejection of 96.4% of 2g/L PEG1500 in deionised water, and so was able to retain unoxidised PEG1500. All concentrations were determined by HPLC and pH was measured during all oxidation experiments. To determine the feasibility of the MemOx system, successive batch oxidation and filtration experiments were carried out to simulate a continuous reactor with a recycle. In this, a batch UV oxidation was firstly conducted. The reactor contents were then filtered, fresh feed was added to the retentate to make it up to the original volume and this solution was recycled back to the UV oxidation reactor and then the process repeated. A new disc of membrane was used for each filtration to minimise the effects of membrane fouling.

Results showed that when compared to standard UV oxidation for the equivalent time period, the rate of oxidation in these batch membrane recycle experiments was at least twice as fast, indicating that the membrane recycle produced a synergistic rate acceleration. On average the pH dropped by 0.3 over 1 hour during every oxidation, indicating that acidic species were being produced. HPLC traces confirmed that these molecules were more polar than PEG1500, indicating that they were most likely the recalcitrant volatile fatty acids produced in such oxidations (such as formic and acetic acid). In all successive batch oxidation and filtration experiments a steady state organic concentration was reached in the reactor which changed with different operating conditions. The UV intensity, temperature, oxidation time, oxidant concentration and recycle ratio therefore need to be optimised in each new application to ensure the permeate (effluent) from the MemOx system is sufficiently oxidised.

Consequently, this preliminary work has demonstrated that a Membrane Enhanced UV oxidation is more effective than standard UV oxidation of wastewater streams, allowing the oxidation system to operate at a higher reaction rate and select a narrower range of molecules into the effluent.

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Drinking and Wastewater Applications III – 4

Wednesday July 16, 11:15 AM-11:45 AM, Maui

Improvement of Swimming Pool Water Quality by Ultrafiltration - Adsorption Hybrid Process

E. Barbot (Speaker), Aix-Marseille University, UMR 6181, France - [email protected] P. Moulin, Aix-Marseille University, UMR 6181, France

Disinfection by-products can be rapidly formed when organic matter is in contact with chlorine (i.e. disinfection of drinking water). Among those compounds, trihalomethanes and haloacetic acids are primarily formed. Since the current standard swimming pool water treatment method involves disinfection by chlorinated compounds, pools are highly susceptible to these reactions. Swimmers introduce a non negligible amount of organic matter, coming from body fluids, skin, hair and cosmetics. Nitrogenous compounds, typically originating from urine and sweat, easily react with hypochlorous acid and lead to the formation of chloramines (NH2Cl and NCl3). The presence of carbonaceous compounds leads to the formation of trihalomethanes, especially chloroform and chloroacetic acids. Chloroform and chloramines are toxic and highly volatile, which means they can rapidly pollute not only the water but also the atmosphere of the pool. Chloramines concentration has been reported to reach 1.85 mg.m-3 in pool air, when the standard long term exposure value is leveled at 0.5 mg.m-3. This chemical pollution is of great concern for the swimming pool staff, who can suffer from pulmonary or ocular irritation and asthma. Early age children are also highly exposed, especially through baby swimmer activities. Specific conditions, such as higher temperature of the water and high pool usage, coupled with physiological characteristics of babies (i.e. very permeable skin) mean that a baby can absorb as much chloroform in one hour than a lifeguard in three weeks.

Thus, this study develops a new process for swimming pool water treatment to meet the three legislation standards of water quality: bacteriological, visual and chemical. Ultrafiltration by hollow fiber was chosen because of its ability to both clarify the water by simultaneously removing bacteria and viruses without chemical compound addition. Molecular weight cut-off (MWCO) of ultrafiltration hollow fiber membrane does not enable the retention of the major part of organic matter introduced into the water, nor the disinfection by-products. Thus it was necessary to couple the ultrafiltration process with an additional one, which could retain organic matter or chlorinated compounds. Adsorption on a specific activated carbon was the process selected for that purpose. Experiments were performed for 18 months in a municipal swimming pool located in Marseille (France). During that time the 100 m3 pool was subjected to a high usage frequency, aquagym and baby swimmer activities. An industrial ultrafiltration unit, with a 115 m2 membrane surface and cellulose acetate hollow fibers was set on

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the current treatment line. A lab-scale adsorption unit followed the filtration. Chlorine components were monitored; in particular, combined chlorine was measured, which gave the concentration of disinfection by-products in the water. Chemical water quality was followed depending on the number of swimmers and activity. It appears that disinfection by-products concentration increases rapidly with pool usage. However with the high variability of the number of swimmers and the difficulty of quantifying their activity, no correlation was found between those parameters. Combined chlorine concentration at the end of the day often exceeds the French standard legislation, showing the non efficiency of the classical treatment. Pool usage also has a high influence on the membrane permeability. A constant and high number of swimmers during one day or baby swimmer activity during 4 hours can involve a permeability decrease of 2.4 L h-1 m-2 bar-1 with each hour of filtration. After 18 months, optimal ultrafiltration operating conditions were found to be at a transmembrane pressure (TMP) of 0.45 bar and a filtration time (Tf) of 60 min for the entire range of each water quality parameter studied. Backwashes appear to be sufficient to maintain membrane permeability when pollution is introduced during a short period. The closure of the pool during night and holidays when combined with filtration/backwashes cycles can lead to the full recovery of permeability. On the contrary, when the pool is subjected to a constant high usage, like during the summer months, backwashes are not sufficient and the permeability constantly decreases. However, permeability never decreased less than 160 L h-1 m-2 bar-1. The adsorption step limited the concentration of combined chlorine in water to 0.35 ppm, well below the limit given by the French legislation (0.6 ppm). When the adsorption material is fresh, active chlorine is readily adsorbed to the surface, but after 24 hours this effect is reduced to less than 50% and the active chlorine standard is maintained.

This hybrid ultrafiltration adsorption process responds well to all the three required criteria of swimming pool water treatment by disinfecting and clarifying while simultaneously reducing the concentration of combined chlorine.

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Drinking and Wastewater Applications III – 5

Wednesday July 16, 11:45 AM-12:15 PM, Maui

Processing of Low- and Intermediate- Level Radioactive Wastes from Medical and Industrial Applications by Membrane Methods

G. Zakrzewska-Trznadel (Speaker), Institute of Nuclear Chemistry and Technology, Warszawa, Poland - [email protected]

The processing of radioactive wastes before ultimate disposal is important taking into account the potential hazard of radioactive substances to human health and surrounding environment. The choice of appropriate technology depends on capital and operational costs, wastes amount and their characteristics, appointed targets of the process, e.g. the values of decontamination factors and volume reduction coefficients. The conventional technologies applied for radioactive waste processing, such as precipitation coupled with sedimentation, ion exchange and evaporation have many drawbacks. These include high energy consumption and formation of secondary wastes, e.g. the sludge from sediment tanks, spent ion exchange adsorbents and regeneration solutions. Membrane processes as the newest achievement of the process engineering can successfully supersede many non-effective, out of date methods. But in some instances they can also complement these techniques whilst improving the parameters of effluents and purification economy. The paper presents the own research data on the application of recent achievements in the area of membrane processes for solving selected problems in nuclear technology in Poland. Particular attention was paid to the pressure- driven processes, e.g. ultrafiltration and reverse osmosis, which were studied on a laboratory and pilot scale. Verification of the potential application of reverse osmosis on an industrial scale for treatment of liquid low- and intermediate-level radioactive wastes has been carried out with the installation designed and constructed for Radioactive Waste Management Plant at Swierk (Poland). The thin-layer composite membranes made from a cross-linked aromatic polyamide of high retention of NaCl (99,4-99,7%) were applied in this process. It has been proved that a three-stage installation enables the radioactive waste of specific radioactivity below 105 Bq/dm3 to be cleaned down to 10 Bq/dm3 in permeate, with simultaneous 7-15-fold reduction of the activity in the concentrate. The results of the own studies concerning the removal of selected radionuclides from model aqueous solutions and radioactive wastes with ultrafiltration enhanced by complexation and sorption were also presented in this work. In these cases, the mineral (ceramic) porous membranes made from alpha-alumina, titanium and zirconium oxides were applied. These membranes exhibited a high resistance against ionizing radiation, aggressive chemical environment and high temperatures. The high effectiveness of removal of the main components of liquid radioactive waste like 134Cs, 137Cs, 60Co, 124Sb, 85Sr, 152Eu and 154Eu with a hybrid

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ultrafiltration/complexation process has been experimentally proved. The effects of this type of complexing agent, its concentration and pH of the processed solution on the complexation effectiveness have been studied. Effectiveness of the method was tested with real radioactive wastes. The paper performs results of the studies on membrane distillation which has been proposed for processing of liquid radioactive wastes, and the analysis of its applicability for nuclear desalination and the production of pure water for power industry purposes. The membranes made from polytetrafluoroethylene and polypropylene were used in the case of membrane distillation. It was proved that membrane distillation is an efficient process in radioactive waste processing, enabling complete purification of the effluent and high volume reduction. The flow- sheet of integrated system for the purification of low and medium level radioactive wastes, combined with nuclear desalination by the membrane distillation method for the purpose of nuclear power plant, has been elaborated. The final conclusions comprise the characteristics and comparison of the applied membrane methods and the evaluation of their efficiency.

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Drinking and Wastewater Applications III – 6

Wednesday July 16, 12:15 PM-12:45 PM, Maui

Removal of Natural Organic Matter in Coagulation-Microfiltration-GAC Adsorption Systems for Drinking Water Production

Y. Ahn (Speaker), KAIST, Daejeon, Korea - [email protected] C. Lee, University of Suwon, Gyeonggi-do, Korea B. Bae, Daejeon University, Daeion, Korea S. Min, Samsung Construction, Kyunggi-Do H. Shin, KAIST, Daejeon, Korea

As the limitations of conventional water treatment processes to meet increasingly stringent drinking water regulations become more apparent, membrane processes are gaining support within water treatment industry as a better means of addressing existing and anticipated regulatory requirements. Generally, the low pressure driven membrane techniques such as microfiltration and ultrafiltration have been considered as indispensable treatment methods in the water treatment applications to remove specific pollutants which cannot be removed by the conventional process. MF and UF are excellent in removing microparticles, microorganisms, macromolecules, colloids and most bacteria. However, they can only partially remove color and dissolved organic matter and synthetic organic compounds. Therefore, the membrane hybrid systems such as membrane-adsorption and coagulation- membrane filtration system are regarded as an alternative way to achieve a high removal efficiency of natural NOM (natural organic matter) and SOC (synthetic organic chemical) in a cost-effective manner (Lebeau et al., 1998). In this study, coagulation and GAC (granular activated carbon) adsorption are applied as a pre- and post treatment process for the microfiltration process. The aim of this study is to minimize disinfection by-product formation potential through the precursor removal and maximize the efficiency of the whole system through NOM characterization. The complicated characteristics of NOM were assessed by various analytical techniques to evaluate their removal efficiency in each process.

The experiments were carried out in laboratory using a bench scale reactor treating 40 litre of surface water per day, and the surface was taken from Wol-Pyeong water treatment plant in Korea. The MF membrane made of PTFE (polytetrafluoroethylene) having a nominal pore size of 0.1 um was submerged in the rectangular basin. Apparent molecular weight distribution was determined using ultrafiltration membranes with a Amicon® cell device (Model 8200, Millipore, USA). The dissolved organic carbon and UV absorbance at a wavelength of 254 nm (UVA254) were measured using a total organic carbon analyzer (Phoenix 8000, USA) and UV-VIS spectrophotometer (DU650, Beckman, USA), respectively

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Preferential removal of hydrophobic NOM fraction was achieved by GAC adsorption compared to transphilic and hydrophilic fractions. This is in agreement with the reported result that the humic fraction (hydrophobic NOM) was preferentially removed by GAC adsorption to the non-humic fraction (Krasner and Amy, 1995). A significant difference in NOM removal between coagulation and the GAC adsorption was found in terms of hydrophobic rejection: less than 30% by coagulation vs. 80% by GAC adsorption. Also small MW fraction of NOM was removed by GAC adsorption, while large MW fraction was mostly removed by membrane filtration. Unlike the coagulation results, medium molecular weight NOM (1k ~ 3k Da) was also effectively removed by GAC filter, which might be caused by the sieving mechanism of filter bed. In terms of disinfection by-product formation potential (DBPFP) removal, both of THMFP (trihalomethane formation potential) and HAAFP (haloacetic acid formation potential) were more effectively removed in the GAC column than coagulation or microfiltration membrane. Especially, the removal of bromide combined DBP (dichlorobromomethane, dibromo- chloromethane) was achieved only in the GAC adsorption due to the low molecular weight of their precursors.

When plotting the ultraviolet absorbance at 254 nm, correlations appeared between the dissolved organic carbon concentration and DBPFP. Both of DOC and THMFP concentration profile showed a similar trend, also the most of organic carbon and THMFP were preferentially removed by GAC adsorption. These correlations can be used for the selective operation of post treatment for microfiltration effluent with high DBPFP. The low R2 value (0.6) of correlation between UVA254 and DBPFP might be due to the low DOC/UVA value (22.8~86.7 mg/L/cm-1) of tested water compared to the previously reported values (Kim et al., 2007). Summarizing the experimental results, coagulation and GAC adsorption are playing a different role in NOM removal. Coagulation preferentially removed hydrophilic, large molecular weight, and THMFP related NOM, while GAC adsorption was responsible for hydrophobic, small molecular weight, and HAAFP related NOM removal. Therefore, combination of coagulation and GAC adsorption seemed to be an essential process to minimize the DBP concentration of treated water in membrane coupled drinking water treatment process.

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Polymeric Membranes II – 1 – Keynote

Wednesday July 16, 9:30 AM-10:15 AM, Moloka’i

Optical Resolution with Chiral Polymaide Membranes

M. Nakagawa, Kyoto Institute of Technology, Kyoto, Japan Y. Ikeuchi, Kyoto Institute of Technology, Kyoto, Japan M. Yoshikawa (Speaker), Kyoto Institute of Technology, Kyoto, Japan - [email protected]

Chirality plays an important role in biological processes. Production of enantiomerically pure compounds has attracted much attention in pharmaceutical industry, agrochemical applications, perfume production, food preparation, and so forth. There are a couple of ways to obtain optically pure enantiomers; one is asymmetric synthesis, the other resolution of racemates. In spite of the advances in asymmetric synthesis of pure enantiomers, the resolution of racemates is still the main method for the production of pure enantiomers in industry. Among chiral separation technologies, membrane processes are regarded as economically and ecologically competitive to other conventional chiral separation technologies. With the exception of optical activity, enantiomers show identical physicochemical properties. From this, physical stereoselectivity is an important factor for chiral recognition and chiral separation. To this end, novel polyamides with chiral environment were synthesized from aromatic diamines and the derivative of glutamic acids. Membranes with chiral environment were prepared from the present chiral polyamides. They showed chiral separation ability. Those abilities were dependent on the absolute configuration of constitutional repeating unit of chiral polyamides. The present results suggest that chiral polyamide membranes have potential to separate racemic enantiomers. The present results indicate the great possibility for practical applications.

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Polymeric Membranes II – 2

Wednesday July 16, 10:15 AM-10:45 AM, Moloka’i

Dehydration of Alcohols By Pervaporation Through Polyimide Matrimid® Asymmetric Hollow Fibers with Various Modifications

L. Jiang (Speaker), National University of Singapore, Singapore T. Chung, National University of Singapore, Singapore - [email protected] R. Rajagopalan, National University of Singapore, Singapore

Membrane development involving material selection and membrane fabrication is the heart for the successful development of pervaporation system applied in high temperature and corrosive environment. Among various polymers applied, polyimide is promising material that has already adopted by some commercial fiber producers for gas separation due to its good thermal and chemical stability. Nevertheless, intensive investigation of its asymmetric membrane, a more favorable structure, for pervaporation application is quite limited.

In this study, Matrimid® polyimide asymmetric hollow fibers have been fabricated and applied for pervaporation dehydration of isopropanol. The effectiveness of thermal annealing at high temperatures and/or chemical crosslinking using 1, 3-propane diamine (PDA) on the separation property of these fibers has been investigated. It is found that an increase in the cross-linking degree results in an increase in separation factor and a decrease in flux. This mainly arises from the restricted polymer chain mobility and redistributed free volume size and number induced by the crosslinking process. XRD characterization confirms a tighter polymer networking in hollow fibers with the crosslinking modification. Thermal annealing alone has failed to improve hollow fiber performance due to the cracks caused by inhomogeneous shrinkage in heating process. Nevertheless, appropriate application of thermal annealing as a pretreatment for crosslinking can produce fibers with the optimal performance. It is believed that the formation of charge transfer complexes (CTCs) within the polymer matrix during heat treatment not only assists polymeric chain packing and rigidification but also facilitates more efficient PDA crosslinking, thus results in higher size and shape discrimination in pervaporation. Apparently, PDA molecules could also fill up and seal the non-selective cracks (defects). Experimental results indicate the combined thermal and chemical modification possibly is an effective method independent of the initial status of the hollow fiber (e.g. defective or defective free) in revitalizing and enhancing the membrane performance. Comparison between the dehydration of different alcohols reveals that a better separation performance could be obtained for alcohols having a larger molecular cross-section.

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Polymeric Membranes II – 3

Wednesday July 16, 10:45 AM-11:15 AM, Moloka’i

New Cross-linked Membranes for Solvent Resistant Nanofiltration

K. Vanherck (Speaker), Centre for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Heverlee, Belgium S. Aldea, Centre for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Heverlee, Belgium P. Vandezande, Centre for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Heverlee, Belgium I. Vankelecom, Centre for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Heverlee, Belgium - [email protected]

No commercial membranes exist yet for applications in certain demanding solvents such as the aprotic solvents N,N-dimethylformamide (DMF), N-methylpyrrolidinone (NMP), N,N-dimethylacetamide (DMAc) and dimethylsulfoxide (DMSO). For solute recovery and solvent purification, industries that commonly use these aprotic solvents generally rely on conventional separation techniques such as energy-consuming distillations or waste-generating extractions. The development of a solvent resistant nanofiltration (SRNF) membrane with a high flux and a low molecular weight cut-off (MWCO) in the aprotic solvents can provide a sustainable alternative for these processes by lowering the economical and environmental costs. Since NMP, DMF, DMAc and DMSO are all good solvents for many polymers, the membrane-forming polymer should be chosen so that it can be modified to be able to withstand these solvents.

The effects of the chemical cross-linking of phase-inversion Matrimid® based membranes on the SRNF performance in different aprotic solvents were investigated. Since it is known that addition of inorganic fillers can significantly improve membrane performance, Matrimid® based membranes filled with nano-sized zeolite precursors were prepared as well. The effect of the filler on the cross-linking reaction was studied.

Cross-linking of this polyimide material was done by immersing the membrane in a bath of 100g/l p-xylylenediamine in methanol. To prevent drying out and collapsing of the pores, the membranes went through a solvent exchange procedure before drying. Pieces of the dried cross-linked membranes were immersed in DMF, NMP, DMAc and DMSO for several days. Filtration tests in IPA with these immersed pieces of membrane showed that 60 minutes of cross-linking time was sufficient to create stable membranes. This was confirmed by ATR measurements, showing a near-to-complete conversion of the imide bonds into amide bonds after 60 minutes immersion in the cross-linking bath. Since this was the case for both the filled and unfilled membranes, the cross-linking

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reaction didn�t seem to be influenced by the fillers. Both types of membranes had previously been optimized for applications in alcohol such as isopropanol. These optimal membranes were reproduced, crosslinked and tested for their performance in DMF, NMP, DMAC, DMSO and THF. The cross-linked membranes showed a remarkable performance in DMF with permeabilities at 6 bar ranging from 0,7 to 5,4 l/m² bar h. Rejections of rose Bengal (1017Da) up to 99% and of methyl orange (327,2 Da) up to 97% were found. Permeability of DMF, NMP and DMAc of filled and unfilled membranes dropped considerably at higher pressures (up to 40 bar), most probably due to compaction of the membrane. This may be resolved by further optimization and fine-tuning of the membrane composition. The long term stability was estimated by 10 h lasting dead end filtrations in DMF, DMSO and THF. The results showed that rejections and permeabilities remained virtually constant after an initial stabilizing period of about one hour.

Overall, these are very promising results. Modified polyimide membranes were created that are stable in a range of aprotic solvents. Both the unfilled polyimide membranes and those filled with nano-sized zeolite precursors have high permeabilities and a good MWCO in these solvents. The easy methodology may allow for a straightforward upscaling of these membranes.

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Polymeric Membranes II – 4

Wednesday July 16, 11:15 AM-11:45 AM, Moloka’i

Properties and Potential of Polymeric Nanofiber Membranes for Liquid Filtration Applications

G. Singh (Speaker), National University of Singapore, Singapore - [email protected] S. Kaur, National University of Singapore, Singapore S. Ramakrishna, National University of Singapore, Singapore N. Wun Jern, Nanyang Technological University, Singapore T. Matsuura, University of Ottawa, Ottawa, Canada

Membrane technology has been hailed as a promising solution in addressing the global water challenges. With increasing costs of fuel and concerns about environmental impacts of various technologies, their energy requirement is becoming an important focal point for governments and industrialists. The future of membrane technology requires the development of more efficient and energy-saving membranes. These next generation membranes should result in better performance i.e. permeation rate or flux at better or the same quality of the permeate i.e. selectivity. Nanofiber membranes represent a new class of membranes, which we have been developing and studying in the last few years. There is good potential for these membranes to be used for liquid filtration. In this paper, the properties of nanofiber membranes are explored and its performance compared with a top-end commercial membrane is evaluated.

Through nanotechnology, it has become possible to produce polymeric fibers in the nanometer range (<1µm), which can be collected as a mesh or membrane. The process used to produce these nanofiber membranes is called electrospinning. By this process, a random mesh of non-woven fibers is formed on the surface, which can be subsequently used after further treatment as nanofiber membranes.

A significant advantage of the nanofiber membrane is its high porosity. We have found that the nanofiber membranes have a porosity of approximately 80%, whereas commercial phase-inverted membranes (HVLP, Millipore) of the same surface pore size distribution only have a porosity of approximately between 40-60%. The nanofiber membrane depicts a more interconnected pore structure than the phase-inverted membrane. This difference in architecture is predicted to have a significant effect on the performance of the membrane. The higher porosity of the nanofiber membrane also indicates its large surface area per unit volume of membrane accessible to the liquid allowing it to serve as an effective depth filter.

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An interesting surface property of the nanofiber membranes is its higher water contact angle as compared to conventional polymeric films made of the same materials. A PVDF nanofiber membrane has an average static contact angle of 145°. In comparison the contact angle of a PVDF film is only about 60-90°. We believe that the surface roughness of the nanofibers and trapped air pockets, given the high porosity of the nanofiber membrane contribute to this increased hydrophobicity. This hydrophobic characteristic of the nanofiber membrane is particularly important in some liquid filtration applications e.g. membrane distillation.

Nanofiber membranes when produced may not have suitable mechanical strength to be used in liquid filtration processes. We have conducted extensive studies on the effect of heat treatment on the nanofiber properties. Tensile strength tests were conducted on two nanofibrous membranes, with one undergoing further heat treatment at 150°C for 3 hours. The heat treated membrane exhibited much higher mechanical strength with an ultimate tensile strength of 8.5 MPa for the heat treated membrane as compared to 0.4 MPa for the non-heat treated membrane. The mechanical strengthening of the heat treated nanofiber membranes, suggests that the structure of the nanofiber membranes changes after heat treatment. Differential scanning calorimetric profiles for the heat treated membranes indicate two peaks unlike the single peak found for non-heat treated PVDF nanofiber membranes. This signaled the presence of a more ordered fiber structure as a result of heat treatment. It was further found that when the heat applied is below the melting point (Tm) of the polymeric material used, it results in the overlapping nanofibers fusing together.

The produced PVDF nanofiber membranes have a pore size distribution of between 4-10.6 µm. This is too large to be compared with commercial microfiltration and ultrafiltration membranes. To reduce the pore size of the nanofiber membranes but still maintain the nanofiber architecture, plasma-induced graft copolymerization of poly(metharcylic acid) on the PVDF nanofiber membrane was carried out. The pore size distribution of the grafted PVDF nanofiber membrane was then found to be similar to a commercial hydrophilic MF membrane of pore size 0.45 µm (HVLP, Millipore). The surface contact angles of both the grafted nanofiber membrane and the commercial hydrophilic membrane were the same at approximately 60°. This allowed a fairer comparison between the membranes. Both membranes were tested for filtration flux using distilled water and the nanofiber membrane had a higher flux compared with the commercial membrane at all pressures tested. The grafted nanofiber membrane had on average fluxes that were 1.6-2.0 times that of the commercial membrane. The higher flux of the nanofiber membrane indicates its potential to be used as a new next generation membrane material for water filtration.

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Polymeric Membranes II – 5

Wednesday July 16, 11:45 AM-12:15 PM, Moloka’i

Perfluoropolymer Membranes for Gasoline Vapor Emissions Reduction

J. Bowser (Speaker), Compact Membrane Systems, Inc., Wilmington, Delaware, USA - [email protected] S. Majumdar, Compact Membrane Systems, Inc., Wilmington, Delaware, USA

The California Air Resources Board (CARB) has required that the 13,000 gasoline stations in California install vapor processing equipment to become compliant with new air quality regulations. The only technology currently certified by CARB for installation in 90% of these stations is an air/vapor separation process based on amorphous perfluoropolymer membranes.

This paper discusses why this class of membrane is ideal for abatement of gasoline vapor emissions and similar applications requiring the separation of volatile organic compounds from atmospheric gasses. Design of the vapor processor for optimal use of the membrane's characteristics will also be discussed.

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Polymeric Membranes II – 6

Wednesday July 16, 12:15 PM-12:45 PM, Moloka’i

Universal membranes for Solvent resistant nanofiltration (SRNF) and Pervaporation (PV) based on segmented polymer network (SPN)

X. Li (Speaker), Centre for Surface Chemistry and Catalysis, Belgium M. Basko, Centre for Surface Chemistry and Catalysis, Belgium P. Du Prez, Ghent University, Ghent, Belgium I. Vankelecom, Centre for Surface Chemistry and Catalysis, Belgium - [email protected]

Segmented polymer networks (SPN) are two- component networks of covalently interconnected hydrophilic/hydrophobic phases of co-continuous morphology. In the case of amphiphilic SPNs, their swelling properties can be easily tuned through their composition and the covalent bonding of the hydrophilic phases to the hydrophobic ones limits the maximal swelling to prevent the swollen network from disintegrating. This mechanical stability together with their particular tunable swelling behavior, crosslinking degree and nano-separated morphology offers a unique combination of properties to use them in membrane applications. In the present work, hydrophilic bisacrylate terminated poly(ethylene oxide) was used as crosslinker for different types of hydrophobic polyacrylates in the synthesis of amphiphilic SPNs. Composite membranes with thin SPN toplayers were prepared by in-situ polymerization. As the support consisted of hydrolyzed polyacrylonitrile, the high chemical resistance of the composite membrane allowed applications of the SPN based membranes in solvent resistant nanofiltration (SRNF) and pervaporation (PV). The membranes show very high retention on Rose Bengal (1017 Da) RB in different solvents, especially in strong swelling solvents such as tetrahydrofuran (THF) and dimethylformamide (DMF). In THF, the membranes have nearly 100% retention for RB. The membranes were used in pervaporation for dehydration of ethanol and isopropanol (IPA) as well. The selectivity of the membranes proved to be greatly dependent on the ratio of hydrophilic and hydrophobic phases of the SPN.

References

1. Koros, W. J.; Ma, Y. H.; Shimidzu, T.; J. Membr. Sci. 1996, 120, 149-159.

2. Vandezande, P.; Gevers, L. E. M.; Vankelecom, I. F. J.; Chem. Soc. Rev. 2008, DOI: 10.1039/b610848m.

3. Bhanushali, D.; Bhattacharyya, D.; Ann. N.Y. Acad. Sci. 2003, 984, 159-177.

4. Shao, P.; Huang, R. Y. M.; J. Membr. Sci. 2007, 287, 162-179.

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5. Erdodi, G.; Kennedy, J. P.; Prog. Polym. Sci. 2006, 31, 1-18

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Biomedical and Biotechnology II – 1 – Keynote

Wednesday July 16, 9:30 AM-10:15 AM, Honolulu/Kahuku

Macroporous Membrane Adsorbers: Correlations between Materials Structure, Separation Conditions and Performance in Bioseparations

M. Ulbricht (Presenting), Lehrstuhl für Technische Chemie II, Universität Duisburg-Essen, Germany - [email protected] J. Wang, Lehrstuhl für Technische Chemie II, Universität Duisburg-Essen, Germany F. Dismer, Institut für Biotechnologie, Forschungszentrum, Jülich, Germany E. von Lieres, Institut für Biotechnologie, Forschungszentrum, Jülich, Germany J. Hubbuch, Institut für Biotechnologie, Forschungszentrum, Jülich, Germany

Separations with membrane adsorbers are a very attractive and rapidly growing field of application for functional macroporous membranes [1,2]. The key advantages in comparison with conventional porous adsorbers (particles, typically having a diameter of >50 µm) result from the pore structure of the membrane which allows a directional convective flow through the majority of the pores; thus, the characteristic distances (i.e., times) for pore diffusion will be drastically reduced. The separation of substances is based on their reversible binding on the functionalized pore walls; the most frequently used interactions are ion- exchange and various types of affinity binding. However, there is still a large interest in improvement of performance for established membranes and in development of novel membranes with higher selectivity [2]. Further, for a better understanding of the complex interplay between mass transfer and reversible binding, a more comprehensive analysis of the (coupled) influences of pore structure and functional binding layer as well as their interactions with the mobile phase, all as function of flow rate, is strongly needed. Here we will present our recent efforts to elucidate influences of the materials and the process conditions onto resulting separation performance.

First, a detailed analysis of pore structure and protein binding in commercial cation-exchange membrane adsorbers (Sartobind®) by conventional and environmental scanning electron microscopy (ESEM) as well as confocal laser scanning microscopy (CLSM) has been performed [3]. The binding of mono-Cy5-labelled lysozyme inside fluoresceine-labelled and unlabelled Sartobind® membranes was monitored by CLSM. The characteristic fluorescence intensity distributions indicated that protein binding takes place predominately in a layer which is anchored to a fine cellulose fiber network. Due to the limited thickness of this binding layer, a significant fraction of the macropores remained free of protein. Protein binding as function of concentration and incubation times was also monitored by CLSM and discussed related to the binding isotherms for the membranes. For the first time, the binding and breakthrough of (dye-labelled) protein within a (dye-labelled) membrane adsorber has been monitored in situ and on-line by using CLSM. Distinctly different breakthrough times have been

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observed for different locations in the x-y plane, and this can presumably help to explain the observed significant dispersion for the same protein in the same membrane in conventional chromatographic experiments (performed in an Äkta system).

Second, various types of new cation-exchange membrane adsorbers with three-dimensional binding layers on macroporous support membranes from regenerated cellulose with 0.45, 1 and 3~5 µm pore diameter had been prepared via photo- initiated graft copolymerization [4]. A well-defined chemical cross-linking of the functional binding layer via addition of a cross-linker monomer during photo-grafting lead to a markedly improved separation performance because higher permeability and lower susceptibilities of permeability to salt concentration than with linear grafted polymer had been combined with high protein binding capacities.

Third, the system dispersion curves (using inert tracer and/or unmodified base membranes) and breakthrough curves (using proteins of various sizes) have been measured for the commercial and the various newly prepared porous membrane adsorbers (with varied pore structure and binding layer). The results will be interpreted in the frame of two models, a macroscopic ‘dead-volume’ model describing the influence of flow distribution in the membrane module, and a ‘dynamic binding’ model describing the interplay between convection through the membrane pores and the binding in three-dimensional (several 100s nm thick) functional layers on the pore walls.

In conclusion, the combination of advanced microscopy with detailed investigations of static and dynamic protein binding provides a better understanding of the coupling between mass transfer and reversible binding in membrane adsorbers onto separation performance, and it yields valuable guide-lines for the development of improved membrane adsorbers and separations based on such materials.

[1] R. van Reis, A. Zydney, J. Membr. Sci. 2007, 297, 16-50.

[2] M. Ulbricht, Polymer 2006, 47, 2217-2262.

[3] J. Wang, F. Dismer, J. Hubbuch, M. Ulbricht, J. Membr. Sci. 2007, submitted.

[4] J. Wang, M. Ulbricht, J. Chromatogr. A 2008, submitted.

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Biomedical and Biotechnology II – 2

Wednesday July 16, 10:15 AM-10:45 AM, Honolulu/Kahuku

Integrated Membrane-Based Sample Prep Approach for Viral and Microbe Capture, Lysis, and Nucleic Acid Purification From Complex Samples

R. Baggio (Speaker), Millipore Corporation, Bedford, Massachusetts, USA - [email protected] K. Souza, Millipore Corporation, Bedford, Massachusetts, USA J. Murrell, Millipore Corporation, Bedford, Massachusetts, USA L. Mullin, Millipore Corporation, Bedford, Massachusetts, USA M. Aysola, Millipore Corporation, Bedford, Massachusetts, USA J. Lindsay, Millipore Corporation, Bedford, Massachusetts, USA G. Gagne, Millipore Corporation, Bedford, Massachusetts, USA C. Martin, Millipore Corporation, Bedford, Massachusetts, USA

The detection of microbial and viral contamination in a timely, simple, and effective manner is a concern of high interest to bioprocess workflows. Anaerobic bacterial and mycoplasma detection based on growth and viral detection based on infectivity assays are notoriously slow, labor intensive, and costly. Our laboratory has developed an integrated membrane-based approach coupled to quantitative PCR (qPCR) for the detection of Pseudomonas aeruginosa, Propionobacter acnes, Mycoplasma hyorhinis,and Minute Virus of Mouse (MVM) in both simple and Chinese Hamster Ovary (CHO) cell loaded samples at levels as low as 100 CFU. In the sample preparation described in this work all cells in the sample are captured and processed. By configuring prefilters, retentive membranes, and affinity membranes in single or stacked interlocking devices more aseptic processing could also be realized. The closed devices have been engineered to be capable of multiple process work involving multiple and discontinuous solution handling. By configuring size exclusion membranes and affinity-based retentive membranes in sequential order, multiple process steps are simultaneously carried out. The approach simplifies sample preparation steps by combining size excluision chromatography and affinity chromatogarphy in a unified membrane-based format. The separate steps of microbe capture, microbe lysis, and nucleic acid purification are all performed in the devices, providing a simplified method of preparation for challenging samples. These results demonstrate the utility of an integrated method for sample preparation from samples that mimic the complex bioreactor environment.

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Biomedical and Biotechnology II – 3

Wednesday July 16, 10:45 AM-11:15 AM, Honolulu/Kahuku

Morphological and Functional Features of Neurons Isolated from Hippocampus on Different Membrane Surfaces

L. De Bartolo (Presenting), Institute on Membrane Technology, National Research Council of Italy, ITM-C, Italy - [email protected] M. Rende, Institute on Membrane Technology, National Research Council of Italy, ITM-C, Italy S. Morelli, Institute on Membrane Technology, National Research Council of Italy, ITM-C, Italy G. Giusi, Comparative Neuroanatomy Laboratory, Department of Ecology, University of C, Italy S. Salerno, Institute on Membrane Technology, National Research Council of Italy, ITM-C, Italy A. Piscioneri, Institute on Membrane Technology, National Research Council of Italy, ITM-C, Italy A. Gordano, Institute on Membrane Technology, National Research Council of Italy, ITM-C, Italy M. Canonaco, Comparative Neuroanatomy Laboratory, Department of Ecology, University of C, Italy E. Drioli, Institute on Membrane Technology, National Research Council of Italy, ITM-C, Italy

Biomaterials such as membranes have become of great interest, since they offer the advantage of developing neuronal tissue that may be used for in vitro simulation of brain function. In an attempt to develop a membrane biohybrid system constituted of membranes and neurons the behaviour of neurons isolated from the hippocampus of the hamster Mesocricetus auratus were studied on membranes with different morphological properties. Polymeric membranes in polyester (PE), modified polyetheretherketone (PEEK-WC), fluorocarbon (FC) and polyethersulfone (PES) coated with poly- L-lysine with different morphological surface properties (e.g., pore size, porosity and roughness) were used as substrate for cell adhesion. Confocal and SEM analyses of cells cultured on the different surfaces demonstrated that in response to varying the roughness of the membrane surface, hippocampal neurons exhibited a different morphology. Indeed cells grown on smoother membranes differentiated with a large number of neuritis with consequent formation of bundles. As a consequence while a very complex network was formed on FC membrane, cells tend to, instead, form aggregates and most of the processes are developed inside the pores of the membranes when rougher PEEK-WC surfaces were used. Metabolic results in terms of glucose consumption, lactate production and BDNF secretion confirmed the effect of roughness on the cell behaviour: neurons exhibited BDNF secretion at high levels on FC membranes with respect to the other membranes. Taken together these results suggest the pivotal role played by membrane roughness in the adhesion and differentiation of the hippocampal neurons and may thus constitute a valuable approach for future neurobiological studies.

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Biomedical and Biotechnology II – 4

Wednesday July 16, 11:15 AM-11:45 AM, Honolulu/Kahuku

Membrane Emulsification Technology to Enhance Phase Transfer Biocatalyst Properties and Multiphase Membrane Reactor Performance

L. Giorno (Speaker), Institute on Membrane Technology, ITM-CNR, Rende, Italy - [email protected] E. Piacentini, University of Calabria, Rende, Italy R. Mazzei, Institute on Membrane Technology, ITM-CNR, Rende, Italy F. Bazzarelli, Institute on Membrane Technology, ITM-CNR, Rende, Italy E. Drioli, Institute on Membrane Technology, ITM-CNR, Rende, Italy

Membrane emulsification is a relatively new technology; it has been developed in the last 20 years and nowadays it can be considered at a good stage of acceptance by stakeholders, with several applications being constantly developed. It is well recognized as a sustainable and efficient technology for precision making of droplets and particles with uniform and controlled size distribution.

In this paper, new feature of direct membrane emulsification will be emphasized. In particular, the droplet formation mechanism of membrane emulsification applied to assist the optimal distribution of phase transfer biocatalysts at the oil-water interface of stable and uniform oil droplets will be discussed. The process is carried out at room temperature, atmospheric pressure and very low shear stress, i.e. conditions that preserve the functional stability of labile macromolecules such as enzymatic proteins.

The process allowed fine and regular dispersion of the enzyme at the interface leading to a very efficient catalyst formulation to the point that unprecedented improved intrinsic catalytic properties are observed. Furthermore, the methodology is accurate enough to allow basic parameters evaluation. For example, the hydrodynamic diameter of macromolecule at the interface could be evaluated and compared to the molecular diameter calculated from crystallographic data.

The unique performance of the formulated biocatalyst were also applied to implement two- separate phase enzyme-loaded membrane reactors. In particular, enantiocatalytic selectivity and stability could be improved and mass transfer of polar/non-polar molecules through the membrane could be modulated.

The methodology opens for a large variety of process implementation in biotechnology, biomedicine, food, waste water treatment. Some major cases

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applied in the first two fields will be outlined to illustrate the technological perspectives.

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Biomedical and Biotechnology II – 5

Wednesday July 16, 11:45 AM-12:15 PM, Honolulu/Kahuku

Anti-Biofouling Membrane Surface with Grafted Zwitterionic Polysulfobetaine for Improved Blood Compatibility

Y. Chang (Speaker), R&D Center for Membrane Technology and Department of Chemical Engineering, Taoyuan, Taiwan - [email protected]

One of the most important requirements for membranes in biomedical applications is to reduce the nonspecific adsorption of biomolecules when living systems encounter membrane surfaces. Biofouling of membranes prepared from hydrophobic materials will lead to a change in biomolecular structure selectively decreasing the permeate flux with time, especially in the filtration of protein, platelet, or cell-containing solutions. In general, ester group in poly(ethylene glycol) (PEG)- based material is the ideal choice of surface functional moiety with anti-biofouling characteristics. However, it has been recognized that PEG decomposes in the presence of oxygen and transition metal ions found in most biochemically relevant solutions. Whereas, PEG exhibits an excellent nonfouling capability, but it faces the problem of long-term stability for biomedical uses. Therefore, materials containing zwitterionic phosphotidylcholine headgroups have become one of the popular synthetic materials for developing anti-biofouling surfaces. Recently, our works have shown that material surfaces containing similar zwitterionic structure to phosphorylcholine, such as sulfobetaine are ideal for resisting protein adsorption when the surface density and chain length of zwitterionic groups is controlled. In our current research, it was further demonstrated that a surface with well-packed grafted zwitterionic polysulfobetaine performs highly stable anti- biofouling properties for plasma protein repulsion. This work is aimed at addressing two important issues for polysulfobetaine (PSBMA) stability, i.e., (i) protein adsorption on PSBMA surfaces at different ionic strengths, solution pH values, and temperatures, (ii) PSBMA blood compatibility in the human body temperature. The results were systematically studied by surface plasmon resonance and will be summarized in the first part of the giving talk. This work concluded that zwitterionic PSBMA provides a significant impact and opportunity in searching for alternative stable nonbiofouling materials other than PEG. In this extended study, the strategy for creating zwitterionic PSBMA surface will be introduced to prepare anti-biofouling membranes. The general idea was performed by two different surface modification approaches for the case of segmented polyurethane (SPU) membrane, which will be presented in the second part of the giving talk. For the first case system, interpenetrating polymer networks (IPNs) on the prepared membrane surface were prepared by the modification of a SPU with a cross-linked sulfobetaine methacrylate (SBMA) polymer. The IPN membrane surfaces that were prepared can effectively resist nonspecific protein adsorption when the

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distribution of SBMA units within the SPU membrane is well controlled, and they retain high mechanical strengths inherent from the base SPU membranes. In this case system, various parameters governing the formation of IPNs containing SBMA were studied. The amount of adsorbed proteins on the IPN membrane was determined by an enzyme-linked immunosorbent assay. Results show that the amount of adsorbed proteins on the IPN membranes depends on the incubation conditions, including solvent polarity, incubation time, SBMA monomer ratio, and incubation concentration. It appears that the IPN membranes prepared in a mixed solvent of higher polarity with long incubation time lead to very low protein adsorption. For the second case system, SPU membranes grafted with PSBMA via surface- activated ozone treatment and thermally induced graft copolymerization. Blood compatibility of the modified SPU membranes was evaluated by the biofouling property of the platelet adhesion observed by scanning electron microscopy (SEM) and the plasma protein adsorption determined by an enzyme-linked immunosorbent assay (ELISA). This study not only determines the grafting quality with PSBMA, but also provides a fundamental understanding of various grafting density governing the effects on the correlation of surface hydration and plasma proteins adoption.

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Biomedical and Biotechnology II – 6

Wednesday July 16, 12:15 PM-12:45 PM, Honolulu/Kahuku

Supported Liquid Membranes with Strip Dispersion for the Recovery of Cephalexin

M. Vilt (Speaker), The Ohio State University, Columbus, Ohio, USA W. Ho, The Ohio State University, Columbus, Ohio, USA - [email protected]

Cephalexin is an important and widely used semi- synthetic cephalosporin. Cephalosprorins along with penicillins are Beta-lactam antibiotics, which account for the majority of the antibiotic world market. Cephalexin is traditionally produced by a 10-step chemical synthesis. An enzymatic synthesis for Cephalexin has been developed, and offers several advantages over the classical route. The enzymatic synthesis reduces energy and solvent waste, but has been used in industrial production on a limited basis. The enzymatic reaction mixture contains Cephalexin, side products, and unconverted reactants, which are similar in structure, are difficult to separate. Liquid membranes, in particular supported liquid membranes (SLMs), are a promising solution to the separation. Reactive extraction with the quaternary ammonium compound Aliquat 336 has been demonstrated for Cephalexin and other semi-synthetic cephalosporins. SLMs are still not used industrially, as they still plagued with problem of long term instability. The SLM with strip dispersion has been a recent development to solve the issue of stability.

SLM with strip dispersion can be described when an aqueous strip solution is dispersed in an organic membrane solution by a mixer, and passed on one side of a membrane support. When a microporous hydrophobic support is used, the organic phase of the dispersion becomes imbedded in the pores of the support, forming a stable SLM. Stability is maintained by having a constant supply of organic membrane solution to the pores.

In this study, Cephalexin has been separated and concentrated from an aqueous solution using the SLM with strip dispersion. Experiments used a Liqui-Cel® hollow fiber module as a microporous support. The organic membrane solution of the SLM consisted of Aliquat 336, Isopar L (isoparaffinic hydrocarbon solvent), and 1- decanol. The aqueous strip solution was composed of potassium chloride and citrate buffer. The following key parameters were investigated: feed and strip dispersion flowrate, strip dispersion mixing rate, carrier concentration, counter ion concentration, pH, and volume of aqueous strip solution. High extraction and recovery rates were achieved when maintaining a proper pH in the aqueous strip solution combined with an excess of potassium chloride. An enrichment factor of up to 3.2 was observed in the aqueous strip solution while achieving over 99% extraction and 96.2% total recovery. In this case, the aqueous feed solution of

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5500 ppm (15 mM) was lowered to 30 ppm when using an organic membrane solution containing 2.5% Aliquat 336. The resulting overall mass transfer coefficient was 1.6 x 10-5 cm/sec. The mass flux of Cephalexin for this system was found to be independent of aqueous feed and strip dispersion flowrates, suggesting a major mass transfer resistance due to chemical reaction kinetics, which is supported by calculated individual mass transfer resistances. The pH of the aqueous strip phase was found to play a more significant role when trying to achieve higher enrichment ratios. It was observed that the highest stripping efficiency occurs when the pH of the aqueous strip phase is between the values of 5 and 6.

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Membrane Modeling III - Process Simulations – 1 – Keynote

Wednesday July 16, 9:30 AM-10:15 AM, O’ahu/Waialua

Biopolymer Transport in Ultrafiltration: Role of Molecular Flexibility

A. Zydney (Speaker), The Pennsylvania State University, University Park, Pennsylvania, USA - [email protected] J. Molek, The Pennsylvania State University, University Park, Pennsylvania, USA D. Latulippe, The Pennsylvania State University, University Park, Pennsylvania, USA

Ultrafiltration is used extensively for the purification and concentration of a wide range of biomolecules including natural proteins, enzymes, diagnostic antibodies, and therapeutic proteins. These proteins typically have a dense hydrophobic core, giving them a highly globular structure with relatively little molecular flexibility. Consequently, the transport characteristics of these biomolecules are traditionally described using a hard sphere analysis accounting for the steric, hydrodynamic, and long-range (electrostatic) interactions in the membrane pores. In contrast, polymer transport in membrane systems has typically been described using models that account for the flow-induced elongation of the flexible polymer chain. There is growing interest in second generation biotherapeutics including PEGylated proteins, in which one or more long polyethylene glycol (PEG) chains are covalently attached to a therapeutic protein, as well as plasmid DNA, with the latter of interest in both gene therapy applications and for DNA-based vaccines. These molecules have more complex, and potentially flexible, morphologies. The objective of this study was to examine the role of molecular flexibility in the transport of these novel biomolecules through semipermeable ultrafiltration membranes.

PEGylated alpha-lactalbumin was produced by covalent attachment of an activated polyethylene glycol, having molecular weight of 5, 10, or 20 kDa. A 3.0 kilobase pair plasmid was obtained from Stratagene and prepared by Aldevron. Ultrafiltration experiments were performed in a stirred cell using composite regenerated cellulose membranes provided by Millipore. Biomolecule transmission was evaluated as a function of both filtrate flux and stirring speed to independently control the degree of concentration polarization and flow-induced elongation. Data were analyzed using both hydrodynamic models for hard-sphere solutes and flow-induced elongation models for flexible polymers.

The extent of plasmid transmission was a very strong function of the filtrate flux, with minimal transmission below a critical value of the flux. This critical flux was in good agreement with theoretical models accounting for the flow-induced plasmid elongation, suggesting that these large plasmids behave as nearly infinitely flexible polymers. In contrast, transmission of the PEGylated proteins at low flux was dominated by hard-sphere interactions, with the polyethylene glycol

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increasing the effective size of the biomolecule. However, there was clear evidence for elongation of the PEGylated proteins at high flux, causing the transmission to depend on both the total molecular weight and the number of polyethyleneglycol chains. These results provide the first quantitative demonstration of the importance of biopolymer flexibility on the ultrafiltration characteristics of these important second-generation biotherapeutics.

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Membrane Modeling III - Process Simulations – 2

Wednesday July 16, 10:15 AM-10:45 AM, O’ahu/Waialua

Effects of Long-Term Membrane Fouling on the Dynamic Operability of an Industrial Whey Ultrafiltration Process

K. Yee (Speaker), UNESCO Centre for Membrane Science and Technology, Sydney, Australia J. Bao, School of Chemical Sciences and Engineering, Sydney, Australia D. Wiley, UNESCO Centre for Membrane Science and Technology, Sydney, Australia - [email protected]

1. Introduction

In the production of whey protein concentrate (WPC) by ultrafiltration (UF), the flowrate and composition of the fresh whey feed often fluctuate. Automatic feedback controllers are implemented in industry to maintain the WPC product within its desired specifications. The manipulated variables of the automatic controllers include the ratios of the retentate and permeate streams that are recycled and mixed with the fresh feed, as well as the amount of diafiltration water added to the process. By adjusting the manipulated variables, the automatic controllers are able to mitigate the effects of fluctuations in feed flowrate and composition.

In order to achieve an optimal economic return from WPC production, the achievable control performance from a given process design needs to be determined before the actual feedback controller is implemented. This intrinsic property of the process design towards automatic control is called dynamic operability. Based on the dynamic behaviour of manipulated variables from an industrial whey UF process, the effects of the number of stages of the process and recycle streams on dynamic operability have been investigated by the authors [1, 2]. However, given that industrial whey UF processes usually operate for 16 hours every day, the effects of long-term membrane fouling on dynamic operability is not well understood. The aim of this study is therefore to investigate the effects of long-term fouling on the dynamic operability of an industrial whey UF process, and the implications on process operation. The study is based on dynamic models of an industrial whey UF process developed by the UNSECO Centre for Membrane Science and Technology.

2. Results and Discussion

Dynamic operability of the industrial whey UF process indicates that the required adjustments in manipulated variables to deliver the same level of control performance increase with time during the 16 hours of operation. Given the physical constraints of the manipulated variables (e.g. recycle ratios are bounded

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between 0 and 1), the automatic feedback controllers are not able to mitigate flucutations in feed flowrate and composition experienced by the whey UF process when long-term fouling becomes significant after long hours of operation.

While mid-run washing is often used during the industrial production of WPC to ensure that the desired specifications of WPC can be delivered in steady state, dynamic operability of the whey UF process suggests that mid-run washing is crucial to maintain the performance of automatic feedback controllers, especially after long hours of process operation.

Modifications in process design, such as the installation of a buffer tank to dampen the flucations of the fresh whey feed before supplying to the UF process, can also improve the achievable control performance of the automatic controllers when long-term fouling is significant. By studying the dynamic operability of the modified design, improvements on the achievable control performance can be assessed even before the modification is actually implemented.

References

[1] K.W.K. Yee, A. Alexiadis, J. Bao and D.E. Wiley, Effects of recycle ratios on process dynamics and operability of a whey ultrafiltration stage, Proceedings of IMSTEC�07, 5 � 9 November 2007, Sydney, Australia.

[2] K.W.K. Yee, A. Alexiadis, J. Bao and D.E. Wiley, Effects of multiple-stage membrane process designs on the achievable performance of automatic control, submitted to the Journal of Membrane Science.

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Membrane Modeling III - Process Simulations – 3

Wednesday July 16, 10:45 AM-11:15 AM, O’ahu/Waialua

CFD Modeling for the Concentration of Soy Protein in an Ultrafiltration Hollow Fiber Membrane System Using Resistance-in-Series Model

A. Rajabzadeh (Speaker), University of Waterloo, Waterloo, Canada B. Marcos, Genie Chimique, Universite de Sherbrooke, Quebec, Canada C. Moresoli, University of Waterloo, Waterloo, Canada - [email protected]

Computational Fluid Dynamics (CFD) is a robust technique for solving conservation equations for momentum (Navier-Stokes), mass (continuity), and heat (energy) simultaneously with minimal simplifications. Detailed local information on the fouling mechanism in hollow fiber ultrafiltration and microfiltartion membrane systems requires a rigorous analysis that CFD can provide. In this study, a CFD model was developed to investigate local flow behavior, concentration profile, and membrane fouling for unsteady-state ultrafiltration concentration operation of soy protein in a hollow fiber membrane. A new resistance model based on the local protein concentration comprising the reversible and irreversible fouling components is proposed. The effects of pH, feed velocity, as well as Trans Membrane Pressure (TMP) on the permeate flux were investigated and results were validated with experimental data for two types of soy proteins, pH 6 and pH 9. The hollow fiber ultrafiltration membrane module was 30 cm in length with 50 fibers of 1mm inner diameter. The retentate was returned back to the feed tank which agitated the feed solution and provided homogenous mixing. The viscosity and the diffusivity of the solution were considered as a function of concentration and pH, respectively. The membrane was assumed to be fully retentive for proteins. Fouling was considered to have no consequence on the flow conditions. Two ordinary differential equations representing the changes in the solution volume and the protein concentration in the feed tank were incorporated to the model. The model predictions and the experimental data revealed that the global resistance for the pH 6 soy protein extract is one order of magnitude larger than for the pH 9 extract. The variation of TMP, pH, and feed velocity will also be discussed in details during the presentation.

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Membrane Modeling III - Process Simulations – 4 Wednesday July 16, 11:15 AM-11:45 AM, O’ahu/Waialua

Hydrodynamic CFD Simulation of Mixing in Full-Scale Membrane Bioreactors with Field Experimental Validation

Y. Wang (Speaker), The University of New South Wales, Sydney, Australia M. Brannock, The University of New South Wales, Sydney, Australia G. Leslie, The University of New South Wales, Sydney, Australia - [email protected]

Membrane bioreactors (MBR) represent the ‘state of the art’ for the treatment of municipal wastewater. The optimisation of MBR units requires knowledge of biological treatment, membranes and hydrodynamics/mixing. Good mixing can ensure the effective use of the entire reactor volume and can affect nutrient removal efficiency. The degree of mixing and membrane configuration (e.g. flat sheets and hollow fibres) affects the output response describing the system’s flow regimes and expressed by the residence time distribution (RTD) profiles. The authors’ research group has investigated the mixing efficiency of pilot scale MBRs [1] and full-scale MBRs [2] with different membrane configurations via RTD analysis. Recently, we have developed a CFD model that has been validated with field experiments to show how membrane configurations can affect mixing conditions in the reactor.

CFD simulations were conducted using the commercial software package Fluent® on a 2.2 MLD hollow fibre membrane MBR in Sydney and a 2.5 MLD double deck flat sheet membrane MBR in South Australia. A 3-dimensional flow field consisting of the interacting phases of water and air were computed using the Eulerian-Eulerian multiphase model. The simulation results showed good agreement with the measured field RTD data. The hollow fibre MBR has a Peclet number of 0.24 and number of completely mixed tanks in series of 1.08, while the flat sheet MBR has a Peclet number of 0.37 and 1.13 of completely mixed tanks in series, which showed that the two MBRs were both close to completely mixed conditions. However, the mixing energy contributed by the mixer, bioreactor and membrane aeration, and recirculation pumps was 55.8 kW in total of the flat sheet MBR while 42.9 kW of the hollow fibre MBR, which indicated that the use of flat sheet membranes was 20% higher in mixing energy to create the same degree of mixing.

In conclusion, the development of MBR CFD model can provide the access to evaluate the effects of membrane configurations on energy consumption with the view of achieving the optimum mixing conditions at the lowest possible energy inputs for the design of large installations.

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References:

[1] Y. Wang, K. W. Ong, M. Brannock, and G. Leslie, Evaluation of Membrane Bioreactor Performance via Residence Time Distributions: Effects of Membrane Configuration and Mixing, Water Science & Technology, 57(3)

[2] M. Brannock, B. Kuchle, Y. Wang, and G. Leslie, Evaluation of Membrane Bioreactor Performance via Residence Time Distributions Analysis: Effects of Membrane Configuration, Presented at the 2nd IWA National Young Water Professional Conference, 4-5 June 2007, Berlin, Germany

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Membrane Modeling III - Process Simulations – 5

Wednesday July 16, 11:45 AM-12:15 PM, O’ahu/Waialua

Hybrid Modeling: An Alternative Way to Predict and Control the Behavior of Cross-Flow Membrane Filtration Processes

S. Curcio (Speaker), University of Calabria, Rende, Italy V. Calabro', University of Calabria, Rende, Italy G. Iorio, University of Calabria, Rende, Italy - [email protected]

The aim of the present paper is to develop a hybrid model predicting the behavior of ultrafiltration process, performed in pulsating conditions. The hybrid model actually consists of two different components: a fundamental, theoretical model describing the unsteady-state transport of both momentum and mass in the module channel and through the membrane, and a very simple cause- effect model, based on an artificial neural network (ANN). The theoretical model, described by a system of partial differential equations solved by Finite Elements Method (FEM), allows predicting the time evolution of concentration polarization and of permeate flux decay as a function of process input variables. The neural model, instead, is used to determine, in a wide range of operating conditions, the functional relationship existing between the concentration of the rejected species adsorbed on the membrane surface and the additional resistance due to the membrane fouling. The main advantage of hybrid modeling actually regards the possibility to describe some well-assessed phenomena, such as concentration polarization phenomena and their dependence on the operating conditions, by means of a fundamental theoretical approach. Some others, like the complex interactions existing between the adsorbed solute(s) and the membrane surface, could be very difficult to interpret and, therefore, to express in terms of proper mathematical relationships. An artificial neural network can make up for this limited knowledge of complex physical phenomena with the identification of rather simple single input single output (SISO) models, based on ANN. The observed reliability of hybrid model predictions suggested the possibility of implementing an advanced control system that could generate proper trans- membrane pressure and feed flow rate pulsations, thus promoting polarized layer disruption and, consequently, membrane performance enhancement. This feedback control system has been developed by the integration of different computational environments, thus resulting in the manipulation of the UF experiments operating conditions as control variables, according to the hybrid model suggestions for a permeate flux enhancement. In particular, the effects of proportional, integral and derivative control actions on the responses of the controlled process have been examined.

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Membrane Modeling III - Process Simulations – 6

Wednesday July 16, 12:15 PM-12:45 PM, O’ahu/Waialua

Artificial Neural Networks Analysis of RO Process Performance: RO Plant Performance and Organic Compound Passage

F. Giralt (Speaker), Universitat Rovira i Virgili, Catalunya, Spain - [email protected] R. Rallo, Universitat Rovira i Virgili, Catalunya, Spain D. Libotean, Universitat Rovira i Virgili, Catalunya, Spain J. Giralt, Universitat Rovira i Virgili, Catalunya, Spain Y. Cohen, University of California, Los Angeles (UCLA)

A neural network based modeling approach was investigated as a means of developing data-driven models for describing RO process performance in terms of flux and salt rejection in addition to evaluating the suitability of RO membranes for rejecting a broad range of organic compounds. The concept of plant �memory� time interval was introduced to capture the time-variability of plant performance. The time interval, for the present case of relatively short-term plant performance variability, was introduced as a unique input variable, along with basic input process operating parameters. ANN model training was carried out with the normalized permeate flux and salt passage for various model architectures and time intervals. Model results demonstrated that plant performance could be described to a reasonable level of accuracy (absolute average errors of less than one percent) with respect to both permeate flux and salt passage with a plant memory time interval. Forecasting of plant performance was also shown to be feasible and with good accuracy with a reasonable memory time interval (as high as ~ 48 hrs). The current approach is providing the basis for developing and incorporating neural network data-driven models in a control strategy and early-warning system of the deterioration of RO plant performance. In this regard, the passage of organics through RO membranes is particularly critical for applications that involve RO membranes in water treatment plants. Neural network models can be effective in generating Quantitative Structure-Property Relations (QSPR) for the organic passage (P), sorption (S) and rejection (R) using the most relevant set of molecular descriptors. In the present work, the approach was demonstrated based on an experimental data set of 50 organics with four different RO membranes. A number of feature selection methods were employed. Pre-screening was carried out, with Principal Components Analysis and SOM of the chemical domain for the study chemicals, as defined by chemical descriptors, to identify the applicability domain and chemical similarities. The QSPR models predicted organic passage, rejection, and sorption within the range of the standard deviations of measurements for the experimental data set of fifty compounds. The application for the approach for compounds of interest, for which experimental data were not available, demonstrated reasonable mass balance closures. The quality of the QSPR/NN

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models developed suggests that there is merit in extending the present approach to develop a comprehensive tool for assessing RO plant performance (with respect to both salt and organic solute removal) in RO water treatment processes.

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Ultra- and Microfiltration I - Transport – 1 – Keynote

Wednesday July 16, 9:30 AM-10:15 AM, Wai’anae

Dynamic Microfiltration: Investigation of Critical Flux Measurement Methods and Improved Macromolecular Transmission

S. Prip Beier (Speaker), CAPEC/Department of Chemical and Biochemical Engineering, Technical University, Lyngby, Denmark G. Jonsson, CAPEC/Department of Chemical and Biochemical Engineering, Technical University, Lyngby, Denmark - [email protected]

Introduction: Membrane fouling can be irreversible, such as adsorption [1], or reversible, such a concentration polarization and cake formation, or a combination. I) Fouling increases the hydraulic resistance of the membrane. Increasing the cross-flow velocity can minimize fouling, but this is expensive due to pumping costs. II) Fouling can change the membrane pore size distribution which can affect the transmission of certain components.

Our dynamic microfiltration set-up is constructed to handle both problems. I) Pumping energy is lowered because the shear at the membrane surface is disconnected from the feed suspension velocity by vibrations. II) The vibrations maintain the pore size distribution. Thus, an initial high transmission of macromolecules can be sustained when the flux is below the critical flux.

The dynamic microfiltration system, which has earlier been tested in filtration of yeast cell suspensions [2] and in separation of alpha-amylase enzymes from yeast cells [3], is tested using different critical flux measurement methods and constant flux experiments. ‘Fouling rate’ and macromolecular transmission are evaluated.

Experimental: The module consists of microfiltration hollow fibers with the skin layer on the outside placed vertically in a bundle. The module can be vibrated vertically at variable frequency and amplitude. The average pore sizes are 0.45E-6 m and the system operates at constant flux. Bakers yeast suspensions and bovine serum albumin (BSA) solutions are used. Results and Discussion: The critical flux determination ‘step-up-down’ method along with a ‘step-up’ method has been investigated. Parameters such as step height, step length and start level are varied and investigated in order to identify and improve a proper procedure for determining a critical flux. For a 8 g/l dry weight yeast cell suspension vibrated at 20 Hz and 1.375 mm amplitude (average surface shear rate around 1200 s-1) the average critical flux value for the different determination procedures is 32 L/(m2h) with a standard deviation of 8 L/(m2h). Thus, because of the relatively large standard deviation it is seen that the determination methods including their operational parameters such as step height, step length and flux

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start level has a huge impact on the critical flux level determined. The experimental critical flux determination methods are further evaluated by running 5-6 hours constant flux experiments below, at and above the experimentally determined critical fluxes. Based on our earlier defined acceptable fouling rate limit of 40 mbar/h [2,3] at the critical flux, the step-up method seem to be the most appropriate. Low flux start level (~ 7 L/(m2h)), a step-height of ~ 2 L/(m2h) and a step length of 5-10 minutes should be applied in order to determine critical fluxes at which operation slightly below makes long term constant flux operation without exceeding a fouling rate of 40 mbar/h possible.

The effect of module vibrations on the transmission of BSA macromolecules has also been investigated. For pure BSA solutions of 0.4 wt%, constant flux filtrations at 20 L/(m2h) yielded a constant BSA transmission around 85 % whereas the transmission without module vibration decreased from an initial value of 67 % to around 45 % after 6 hours of constant flux filtration at 20 L/(m2h). The BSA transmission was also investigated in the separation from yeast cells. A 8 g/L dry weight yeast cell suspension with 0.4 wt% BSA was filtrated at 20 L/(m2h). It was possible to retain yeast cells completely and obtain a BSA containing permeate with a constant BSA transmission of around 70 %.

Conclusion: A step-up method with a flux start level of around 7 L/(m2h), a step height of around 2 L/(m2h) and a step length between 5-10 minutes is appropriate for critical flux determination. This method yield critical fluxes that when running constant flux filtrations for 5-6 hours slightly below the critical flux do not exceed a defined critical flux fouling rate limit. Module vibrations facilitate constant BSA transmission and the ability to completely separate yeast cells from BSA with a constant BSA transmission of around 70 %. Overall the dynamic microfiltration system is able to reduce fouling problems and enhance the critical flux by module vibrations. Thus, pumping energy consumption is reduced. Furthermore, constant and high macromolecular transmission is possible.

References:

[1] S.P. Beier, A.D. Enevoldsen, G.M. Kontogeorgis, E.B. Hansen, G. Jonsson, Adsorption of Amylase Enzyme on Ultrafiltration Membranes, Langmuir 23 (2007) 9341-9451.

[2] S.P. Beier, G. Jonsson, M. Guerra, A. Garde, Dynamic Microfiltration with a Vibrating Hollow Fiber Membrane Module; Filtration of Yeast Suspensions, J. Membr. Sci. 281 (2006) 281-287.

[3] S.P. Beier, G. Jonsson, Separation of Yeast Cells and Enzymes with a Vibrating Hollow Fiber Membrane Module, Sep. Purif. Technol. 53 (2007) 111-118.

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Ultra- and Microfiltration I - Transport – 2

Wednesday July 16, 10:15 AM-10:45 AM, Wai’anae

An Integral Analysis of Crossflow Filtration

R. Field (Speaker), University of Oxford, Oxford, United Kingdom J. Wu, University of Durham, Durham, United Kingdom - [email protected]

Hermia’s analysis of dead-end filtration (in which he introduced four values of n, (n-2 complete pore blocking; n=1.5 standard pore blocking; n=1 incomplete pore blocking; n=0 cake filtration) was extended by Field et al (JMS 1995) to crossflow filtration who linked the removal terms to the concept of critical flux. However equating the critical flux to the steady-state flux needs to be questioned; the removal term during initial fouling will not be the same as that after a cake has formed. This mode of analysis also has one other fault and that is the use of flux (J) and time (t) plots. Distinguishing between one form of fouling on the basis of fits to J-t data can be problematic. Although the use of dJ/dt data should in principal be very informative, the noise in typical data is a major problem.

Besides examining the theoretical basis of the terms employed, a novel integral analysis is introduced for crossflow data. It is based upon combinations of volume collected per unit area (V), time (t) and functions of J. The plots that are created enable one to distinguish much more clearly between the various forms of fouling. Linear behaviour is found if the fouling corresponds to a given mode of fouling. Switches in the mode of fouling can readily be identified. A number of examples including yeast filtration, protein filtration and oily-water filtration will be covered.

The advantages and (fewer) disadvantages of this new approach will be discussed with candor.

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Ultra- and Microfiltration I - Transport – 3

Wednesday July 16, 10:45 AM-11:15 AM, Wai’anae

Flux Recovery During Infrasonic Frequency Backpulsing of Micro- and Ultrafiltration Membranes Fouled with Dextrin and Yeast

D. McLachlan (Speaker), UNESCO Assoc Centre for Macromolecules, Shellenbosch, South Africa - [email protected] E. Shugman, UNESCO Assoc Centre for Macromolecules, Shellenbosch, South Africa R. Sanderson, UNESCO Assoc Centre for Macromolecules, Shellenbosch, South Africa

The fouling of micro and ultra membrane filters during the filtration process necessitates that they be cleaned regularly. Back pulsing cleaning, as presented in this paper, has the advantage that the plant does not have to be shut down and that there are no soaps to dispose of.

In this paper Micro and Ultra membranes (Alpha Laval polysulphone 0.1 micron and 100 000 MWCO) are first fouled, using a feed pressure of 100 kPa, in a flat cell, with Dextrin or Yeast. After this infrasound backpulsing, directly into the permeate space, was used to clean the membrane. During the cleaning, the RO feed pressure remained at100 kPa and the cross flow rate at 30lt/hr. The back pulsing was done using permeate water and at peak pressures of 90, 140 and 180 kPa. The results to be given in the presentation show that flux values of over 80% of the clean water value, can be restored by this procedure. These results also show that when applied correctly regular and frequent backpulsing can maintain an overall higher flux.

The purpose of this work is to explore the efficiency of cleaning, various combinations of membrane materials and foulants, using backpulsing in flat cells, where changes can easily be effected. Work is done in conjunction with these experiments, is the use of backpulsing to clean spiral wrap elements (see R D Sanderson et al-these proceedings.)

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Ultra- and Microfiltration I - Transport – 4

Wednesday July 16, 11:15 AM-11:45 AM, Wai’anae

Electrostatic Contributions in Binary Protein Ultrafiltration

Y. Wang (Speaker), University of California Riverside, Riverside, California V. Rodgers, University of California Riverside, Riverside, California - [email protected]

The objective of the current research is to investigate the important electrostatic effects on binary protein ultrafiltration (UF) performance via factors such as system pH and ionic strength. Four proteins were used in this study: alpha-lactalbumin (aLA, 15 kDa), hen egg lysozyme (HEL, 15 kDa), cytochrome C (CytC, 15 kDa) and bovine serum albumin (BSA, 69 kDa). Cross-flow UF experiments (with diafiltration) were conducted for three binary protein systems: aLA/BSA, CytC/BSA and HEL/BSA. These systems were chosen due to their similar protein/protein size ratio however different charge properties, so they were ideal systems to study the non-solute-size effects, especially electrostatic effects, in binary protein UF. The membrane used in all experiments was 30,000-MWCO composite regenerated cellulose (CRC) membrane. This type of membrane has been known for its low extent of fouling, therefore, membrane fouling contributions can be minimized in the current research. The experiments were conducted at various pH values (pH 4.7, pH 6, pH 7, pH 8 and pH 10), and low to moderate ionic strengths (0.0015 M, 0.015 M and 0.15 M). During the experiments, the applied operating hydraulic pressure was varied randomly in the range from 0 to 145 kPa, and the permeate flux versus pressure dependence profiles, as well as the corresponding protein sieving behaviors, were recorded.

The pH and ionic strength dependences of the permeate flux were first observed in the single BSA UF experiments that served as controls. The permeate flux generally increased with increasing pH (which corresponds to the increase of BSA net charge), and decreased with increasing ionic strength. For the binary protein UF experiments, the permeate flux behaviors differed largely from system to system, as expected. For the aLA/BSA system in which aLA was similarly charged as BSA at all pH values studied, the flux-pressure behaviors were almost identical to those of the control experiments with BSA only. On the other hand, for the HEL/BSA system consisting two proteins that were always oppositely charged at the pH values studied, the permeate flux-pressure behaviors differed largely from control experiments. At lower ionic strengths, the significant pH dependence as well as unusual patterns in the permeate flux-pressure profiles strongly suggested reversible formation of HEL-BSA complex caused by electrostatic interaction. Though less significantly, the CytC/BSA system showed similar flux behaviors as the HEL/BSA system. The observed sieving coefficient (as a function of the permeate flux) of the 15 kDa proteins for

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all three binary protein UF systems also demonstrated clear pH and ionic strength dependences, as well as system dependence.

The free solvent-based model (FSB) previously developed by our group, which successfully predicts and characterizes of the flux behavior in protein UF with moderate electrostatic screening, was modified to include electrostatic contributions, and was applied to the theoretical modeling of the observed experimental observations. The FSB model uses the free-solvent model for osmotic pressure [Ref. 1] coupled with the Kedem-Katchalsky model and film theory, and in a paradigm shift, this model reestablishes the significance of osmotic pressure by examining its contribution to permeate flux behavior in the framework of the free-solvent model. The modified film theory [Ref. 2], which includes a permeate flux contribution resulted from the electrostatic forces on the solute particles in the concentration polarization layer, was used to study the pH and ionic strength dependences observed in single BSA UF flux behaviors. Through this approach, the regressed protein surface potential values for each solution condition agreed with the literature reasonably well; however, the limitations of this approach were also recognized. Hindered transport theory [Ref. 3] with electrostatic contribution was used to study the electrostatic interaction effects on the sieving behaviors in binary protein UF. For the aLA/BSA system that only contains repulsive interactions, the model calculations agreed well with the experimental observations. For the other two systems that contain attractive interactions, theoretical modeling is currently on-going.

In summary, the effects of electrostatic contributions in the UF performance of binary protein UF experiments were systematically studied. Theoretical approaches have also demonstrated preliminary success. Results will be discussed.

Ref. 1: M.A. Yousef, R. Datta, and V.G.J. Rodgers, J. Colloid Interface Sci., 197 (1998) 108-118.

Ref. 2: R.M. McDonogh, A.G. Fane, and C.J.D. Fell, J. Membr. Sci., 43 (1989) 69-85.

Ref. 3: W.M. Deen, AIChE Journal, 33 (1987) 1409-1425.

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Ultra- and Microfiltration I - Transport – 5

Wednesday July 16, 11:45 AM-12:15 PM, Wai’anae

Membrane Separation of High Added Value Milk Proteins

M. Mier (Speaker), University of Cantabria, Spain R. Ibáñez, University of Cantabria, Spain I. Ortiz, University of Cantabria, Spain - [email protected]

High Performance Tangential Flow Filtration (HPTFF) is an emerging technology that employs a new kind of porous membranes of recent development [1, 2]. The novelty of these membranes is the fact that they have a net charge either positive or negative. HPTFF claims to be a two-dimensional purification method that exploits differences in both size and charge characteristics of molecules [3], thus, enhancing the efficiency of difficult separations.

First applications of HPTFF dealt with the separation of biomolecules similar in size but different in charge as BSA / Fab; IgG / BSA or myoglobin. [2, 3]. HPTFF is expected to be a good alternative to traditional protein purification processes due to its unique characteristics and its ability to separate molecules with, virtually, the same size taking advantage of their differences in charge. The increasing interest of the food and pharmaceutical industry in the separation of pure protein fractions with nutraceutical properties motivates the development of new membrane separation technologies and the introduction of more efficient processes including different membrane technologies working in conjunction.

In previous works carried out by our research group, the suitability of electrodialysis with bipolar membrane technology (EDBM) for pH control of liquid fluids without the employment of chemical reagents have been demonstrated [4 - 6]. In this basis, this work aims to achieve the pH control of a organic matrix solution (milk) prior the HPTFF processing so that, taking advantage of both membrane technologies, the separation of minor whey proteins into different pure fractions can be achieve minimizing the use of chemicals.

In a first stage the evaluation of the performance of HPTFF membrane technology in the separation of minor whey proteins is studied. Commercial available membranes and prototype charged membranes are tested in order to determine the viability of using HPTFF for difficult separations as similar size protein mixtures but different in their isoelectric point (pI). In a second stage, EDBM is used in combination with HPTFF to achieve selective separation. Using solutions containing mixtures of proteins the solution pH is changed by means of EDBM allowing the selective protein fractionation performed by HPTFF.

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Synthetic solutions of ±-lactalbumin (140kDa - pIH4.5), bovine serum albumin (BSA) (69kDa - pIH4.8) and lactoferrin (78kDa - pIH8) are used in this study. EDBM experiments are carried out by means of a laboratory scale plant purchased by Elektrolyse Project (Netherlands). Commercial anionic and cationic (Ralex AMH and CMH) and bipolar membranes (NEOSEPTA BP-1) are used. HPTFF experiments are carried out by means of a laboratory scale plant from Millipore using BIOMAX and prototype membranes from Millipore.

Finally, a hybrid process combining both membrane technologies, EDBM and HPTFF, will be proposed and tested for the separation of whey proteins.

Bibliography

[1] R. van Reis, S. Gadam, L.N. Frautschy, S. Orlando, E.M. Goodrich, S. Saksena, R. Kuriyel, C.M. Simpson, S. Pearl, A.L. Zydney, High performance tangential flow filtration, Biotechnology and Bioengineering 56 (1997) 71-82.

[2] R. van Reis, J.M. Brake, J. Charkoudian, D.B. Burns, A.L. Zydney, High-performance tangential flow filtration using charged membranes, Journal of Membrane Science 159 (1999) 133-142.

[3] C. Christy, G. Adams, R. Kuriyel, G. Bolton, A. Seilly, High-performance tangential flow filtration: a highly selective membrane separation process, Desalination 144 (2002) 133-136.

[4] M.P. Mier, R. Ibáñez, I. Ortiz, Influence of ion concentration on the kinetics of electrodialysis with bipolar membranes, Separation and Purification Technology 59 (2008) 197 - 205.

[5] M.P. Mier, R. Ibáñez, I. Ortiz, Electrodialysis with bipolar membranes as an efficient method for the obtention of milk proteins, Récents Progrès en Génie des Procédés 94 (2007).

[6] M.P. Mier, R. Ibáñez, I. Ortiz, Influence of process variables on the separation of casein from milk by Electrodialysis with Bipolar Membranes, Biochemical Engineering Journal DOI: 10.1016/j.bej.2007.12.023.

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Ultra- and Microfiltration I - Transport – 6

Wednesday July 16, 12:15 PM-12:45 PM, Wai’anae

Tuning of the Cut-Off Curves By Dynamic Ultrafiltration

G. Jonsson (Speaker), Technical University of Denmark, Lyngby, Denmark - [email protected]

Ultrafiltration is mainly used to concentrate macromolecules and removing salts and smaller molecules through the membrane. Sharp separation is rarely seen which is partly due to the coupling of solute and water transport and the concentration polarization at the membrane surface. In case of real fractionation of macromolecules, a decoupling of the solute transport from the water transfer together with a minimization of the concentration polarization of the larger molecules, have to take place. Using hollow fiber membranes under high- frequency backflushing the concentration polarization can be minimized due to the non- steady state operation. The build-up of the polarized highly concentrated layer at the membrane surface takes typically 10-30 seconds why it is possible to obtain a dynamic layer with a substantially reduced surface concentration thereby increasing the selectivity of the membrane. The paper describes the modeling of the dynamics of the concentration polarization and how it influences the membrane selectivity and productivity. The modeling is further supported by experiments fractionating dextrans and proteins on a hollow fiber system using backflushing intervals from 1 to 30 seconds and backflushing times from 0,1 to 5 seconds.

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Oral Presentation Abstracts

Morning Session

Thursday, July 17, 2008

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Gas Separation IV – 1 – Keynote

Thursday July 17, 8:15 AM-9:00 AM, Kaua’i

Polymer-based Multicomponent Membranes for Gas Separation

K. Peinemann (Speaker), GKSS-Forschungszentrum Geesthacht GmbH, Geesthacht, Germany - [email protected]

In spite of significant developments of polymeric membranes for gas separation it seems that the race for better tailor made organic polymers with improved performance has slowed down during the last years. New developments in the area of hybrid materials (inorganic/organic, organic/organic) have instead stimulated membrane research. In recent years the phrases nanocomposites and nanostructured membrane materials have become the magic formula to attract attention. Some of the scientific achievements, which have been made in this field, will be highlighted. But in spite of these achievements very few (any?) of the sophisticated new materials have found their way into technical applications. Some will but many will never, because they are too complicated for large scale applications. This will be discussed using the example of carbon dioxide capturing. Nanostructured fixed-carrier membranes e.g. show fascinating performance in lab scale experiments but it is highly unlikely that they will be used for natural gas or flue gas treatment. Crossing the Robeson line should not the main criterion for development of a successful gas separation membrane. The author will discuss simple approaches for manufacturing nanocomposites for gas separation.

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Gas Separation IV – 2

Thursday July 17, 9:30 AM-10:00 AM, Kaua’i

Gas Separation Properties of C/SiO2/alumina Composite Membranes for CO2 Separation

S. Han (Speaker), Hanyang University, Seoul, Korea S. Kim, Hanyang University, Seoul, Korea H. Park, University of Ulsan, Ulsan, Korea Y. Lee, Hanyang University, Seoul, Korea [email protected]

Membrane-based gas separation is one of the promising separation technologies due to its high energy efficiency as well as excellent separation property. During the last several decades, polymer materials like polysulfone, poly (ether sulfone), and polyimide have been used for gas separation membrane. Recently, many researchers have shown interests in carbon membranes rendered from polymeric precursors as good candidate materials for gas separation with their superior separation performances, highly excellent stabilities for vapor and condensable gases, and extraordinary durability in heated and corrosive circumstance. In our previous study, we developed carbon-silica(C/SiO2) membranes for enhanced permeabilities of small gas molecules. The C/SiO2 membranes derived from poly(imide siloxane) copolymers were composed of the dispersed silica domains to give higher permeable region as well as the continuous carbon matrix to retain the selectivities of common carbon membranes. We have modified the C/SiO2 materials by UV treatment, by changing the ratio of siloxane domain to polyimide region, by adding sol-gel solution of alkoxysilane, or, by partial oxidation of siloxane domain in pyrolysis to obtain the most suitable membrane for CO2 separation. Furthermore, we have studied to develop the composite membrane coated on porous supports for large areas of inorganic membrane and practical applications. Here, we would like to demonstrate the gas permeation properties of supported carbon composite membrane modules prepared from polyimide and poly(imide siloxane) to fabricate a large inorganic membrane and to test their CO2/N2 separation properties for CO2 sequestration in flue gases. For preparing poly(imide siloxane) as polymeric precursors, a calculated amount of pyromellitic dianhydride(PMDA) was dropped to equimolar 4,4'- oxydianiline(ODA) and aminopropyl dimethylsiloxane (PDMS, Mw=900) solution in 1- methylpyrrolidinone (NMP) and tetrahydrofuran (THF). The alumina support(O.D. = 4.8 mm, I.D. = 3.0 mm, length = 400 mm) purchased from Nanoporous materialsTM were slip-casted by boehmite sol and calcinated at 700 C to prepare mesoporous intermediate layer. The prepared polymeric precursors were coated on the alumina supports modified by alumina layer, and the composite membranes were carbonized at

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600 C in a tubular furnace. Finally, a carbon membrane module was fabricated by sustainable stainless (SUS 316) housing and VitonTM O-ring for permeation test at high temperature. The effective area of carbon membrane module composed of 19 composite membranes was 1002.8 cm2. Gas permeation properties of pure gases were recorded to GPU unit by MFCs (mass flow controllers) and Baratron™ manometers at 1 to 5 atm. Mixed gas separation experiments were conducted by using binary gas mixtures(21% O2/79% N2, 15% CO2/85% N2, 50% CO2/50% CH4), and the compositions of permeate and retentate flow were measured with different stage-cuts by gas chromatography (GC- 2010 ATF, Shimadzu Co. Ltd., Japan) at room temperature to 150oC. The uniform mesoporous ³- alumina layer and defect-free carbon layer coated on the alumina support were 1-2 μm and 2-3 μm thick. Gas permeances of He, H2, CO2, O2, N2, CH4 were 207, 310, 169, 39, 6.1, and 2.7 GPU(1GPU=10- 6 cm3-cm-2-sec-cmHg), respectively. Ideal gas selectivities of the composite membrane were 7 and 27 to O2/N2 and CO2/N2 at 298 K, similarly with the factors calculated from gas permeabilities of flat carbon membranes by time- lag method in our previous study. The gas permeances increased at higher temperature, whereas the selectivities slightly decreased. For binary gas mixtures, composition (yi : conc. at inlet, yp : conc. at permeate, yr : conc. at retentate) and flux (Vi : flux at inlet, Vp : flux at permeate, Vr : flux at retentate) were recorded to calculate the stage-cut and recovery ratio. Stage-cut, the ratio of permeate flux(Vp) divided by inlet flux(Vi), provides information related to the capacity of a membrane module. The larger stage-cut indicates that large amount of feed gas can be supplied at a constant pressure, while the enrichment of the permeate stream should drop proportionally to the increasing stage-cut. Recovery ratio, the ratio of the recovered gas flux per supplied gas flux at inlet stream, is the value of stage-cut multiplied by the permeate concentration. Therefore, the recovery ratio approaches to 1 at higher stage-cut. In CO2/N2 separation test, the enriched CO2 concentration dropped from 85 to 15% at the stage-cut of 0 to 1, while the recovery ratio of CO2 approached from 0 to 1. At the optimized stage-cut of 0.25, the recovery ratio and the permeate composition were 0.9 and 60% CO2.

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Gas Separation IV – 3

Thursday July 17, 10:00 AM-10:30 AM, Kaua’i

Gas Transport Properties of Hyperbranched Polyimide-Silica Hybrid Membranes

Y. Yamada (Speaker), Kyoto Institute of Technology, Kyoto, Japan - [email protected] K. Itahashi, Nagoya Institute of Technology, Nagoya, Japan T. Suzuki, Nagoya Institute of Technology, Nagoya, Japan

Physical and gas transport properties of hyperbranched polyimide silica hybrid membranes were investigated. Hyperbranched polyamic acids as precursors was prepared by polycondensation of a triamine, 1,3,5-tris(4-aminophenoxy) benzene (TAPOB), and commercially available dianhydrides, and subsequently modified a part of end groups by 3-aminopropyltrimethoxysilane (APTrMOS). The hyperbranched polyimide silica hybrid membranes were prepared by sol-gel reaction using the polyamic acids, water, and various alkoxysilanes. 5 % weight-loss temperature of the hybrid membranes increased with increasing silica content, indicating effective crosslinking at polymer silica interface mediated by APTrMOS moiety. On the other hand, glass transition temperature of the hybrid membranes prepared with methyltrimethoxysilane (MTMS) showed a minimum value at low silica content region, suggesting insufficient formation of three-dimensional Si-O-Si network compared to the hybrid membranes prepared with tetramethoxysilane (TMOS). CO2, O2, N2, and CH4 permeability coefficients of the hybrid membranes increased with increasing silica content. Especially for TMOS/MTMS combined system, the hybrid membranes showed simultaneous enhancements of gas permeability and CO2/CH4 separation ability. It was concluded that the hyperbranched polyimide-silica hybrid membranes have high thermal stability and excellent CO2/CH4 selectivity, and are expected to apply to high-performance gas separation membranes.

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Gas Separation IV – 4

Thursday July 17, 10:30 AM-11:00 AM, Kaua’i

Carbon Membranes - Tackling the Aging Issue

E. Sheridan (Speaker), Norwegian University of Science and Technology, Trondheim, Norway J. Lie, Norwegian University of Science and Technology, Trondheim, Norway X. He, Norwegian University of Science and Technology, Trondheim, Norway M. Hägg, Norwegian University of Science and Technology, Trondheim, Norway - [email protected]

Carbon membranes are generally found to out- perform polymeric membranes in relation to selectivity, permeability and stability in highly corrosive and high temperature environments hence making them suitable candidates for processes such as pre-combustion separation of CO2 from natural gas and biogas upgrading. Although carbon membranes have been intensively researched over recent years, the development for commercially application has been hampered somewhat due to the high cost of commonly used precursor materials such as polyimides, the energy demanding carbonization process and the deterioration of performance over time due to membrane aging. The production of carbon membranes as hollow fibres offers a real potential for commercialisation although the major problem of membrane aging must first be addressed.

Our current work attempts to overcome some of the practical problems, by producing carbon hollow fibres by a dry-wet spinning process using a relatively cheap cellulosic precursor and investigating techniques to overcome membrane aging while enhancing membrane performance. Two approaches to defeating the aging effect on carbon membranes are examined. Firstly, the effect of carrying out the carbonization process in different gas atmospheres is investigated. Secondly, the investigation of electrothermal regeneration of the carbon membrane fixed in a module is presented. Results have shown that a carbon membrane may be restored to within 90-100% of its original permeability after this regeneration compared with a loss of 40% for the non-treated membrane. Additional considerations concerning a suitable module design to facilitate electrothermal regeneration are also presented.

The enhancement of the lifetime of carbon membranes through techniques such as regeneration is a key factor in commercialisation of these membranes. In addition, if the above issues are resolved, carbon membranes could surpass the usefulness of polymeric membranes due to their durability in harsh, high temperature environments.

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Gas Separation IV – 5

Thursday July 17, 11:00 AM-11:30 AM, Kaua’i

Glassy Perfluoropolymer - Zeolite Hybrid Membranes for Gas and Vapor Separations

G. Golemme (Speaker), Univ. della Calabria; ITM-CNR; and INSTM, Rende (CS), Italy - [email protected] J. Jansen, ITM - CNR D. Muoio, Univ. della Calábria, Rende, Italy G. De Luca, Univ. della Calábria, Rende, Italy A. Bruno, Univ. della Calábria, Rende, Italy R. Manes, Dip, Univ. della Calábria, Rende, Italy J. Choi, University of Minnesota, Minneapolis, Minnesota M. Tsapatsis, University of Minnesota, Minneapolis, Minnesota

This paper reports on the successful preparation of hybrid membranes of glassy perfluoropolymer and MFI zeolites, with significantly improved transport properties compared to the pure polymers. Perfluoropolymers withstand easily temperatures beyond 100°C, organic solvents and aggressive chemicals. As a result of the unusual sorption properties of glassy and amorphous perfluoropolymers, the permeability-selectivity combinations of some gas pairs exceed the Robeson upper bound [1,2]. Nanoscale fumed silica as a filler of highly permeable, stiff backbone polymers (Teflon AF 2400, PMP, PTMSP) was found to increase the free volume due to the disruption of the packing ability of the organic phase [3-6]; in Teflon AF 2400 and PMP, the increased free volume in turn was responsible of a higher permeability, especially for the most condensable species, and therefore, at the same time, of a better n-butane/CH4 separation factor.

Since porous fillers may have an even better effect on the performance of hybrid membranes than dense fumed silica, the scope of the present work was to study the separation capabilities of Teflon AF and Hyflon hybrid membranes with Silicalite-1 (MFI) crystals of different size. In the past it was demonstrated that surface modified sub-micron zeolites can be effectively dispersed inside the extremely hydrophobic matrix of glassy perfluoropolymer membranes [7]. Hybrid membranes containing up to 42 wt % of fluorophilic MFI crystals (80 to 1500 nm) were thus prepared. Their morphology was observed by SEM and TEM. Single gas permeation experiments (O2, N2, H2, He, CH4, CO2, n-butane) were carried out at 25°C and 1 bar of feed pressure in a constant volume - variable pressure device [8]. The gas diffusion coefficients were derived from the time-lag, the permeability from the steady state pressure increase rate, and the solubility from the permeability-to-diffusion ratio.

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Defect free membranes could be prepared in all cases. In Teflon AF 1600, the noteworthy increase of the gas solubility (especially CO2, CH4 and N2) indicated an active contribution of the MFI crystals to the transport of penetrants. Experimental evidences indicated the presence of a polymer-zeolite interface characterized by higher free volume and permeability. At the same time, the surface of the crystals probably offers a resistance to transport.

MFI fillers improve the separation performance of the poorly selective Teflon AF polymers. In fact the n-butane permeability of a membrane made of 1500 nm MFI crystals (40 wt%) in Teflon AF 2400 was 2230 Barrer, with an ideal n-C4/CH4 separation factor of 2.4, and a solubility selectivity of 38. A comparable membrane of the same polymer containing 40 wt% of amorphous silica, instead, in the same conditions had a lower n-C4 permeability (690 Barrer) and an ideal n-C4/CH4 separation factor of only 0.63 [3]. Mixed gas permeation experiments are now in progress.

Also for the more selective and less permeable Hyflon AD 60X polymer, the main effect of the MFI filler (1500 nm, 42 wt%) is the enhancement of solubility. A CO2 permeability of 500 Barrer and a CO2/CH4 ideal selectivity of 23 represent an interesting combination for the sweetening of natural gas, thanks to the resistance to plasticization of the polymer and also to the stabilizing effect of the inorganic phase [3]. The permeability-selectivity combination of the N2/CH4 gas pair (2.9 ideal selectivity, 63 Barrer for N2) also lies beyond the Robeson 1991 upper bound [2].

In conclusion, this study demonstrates that dispersing porous fillers in perfluoropolymer membranes is a viable principle for the improvement of their separation properties. For some gas pairs the original size selectivity of the pure polymer may be transformed in solubility selectivity in the hybrid material, which opens up new opportunities for the treatment of natural gas.

References

1. T. C. Merkel, I. Pinnau, R. Prabhakar, B. D. Freeman; "Gas and Vapor Transport Properties of Perfluoropolymers", in Yu. Yampol'skii, I. Pinnau, B. D. Freeman, Eds., Materials Science of Membranes for Gas and Vapor Separation; J. Wiley: Chichester (UK), 2006; Chapt. 9, pp. 251- 70.

2. L. M. Robeson, J. Membrane Science, 62 (1992) 165.

3. T. C. Merkel, Z. He, I. Pinnau, B. D. Freeman, P. Meakin, A. J. Hill; Macromolecules, 36 (2003) 8406.

4. T. C. Merkel, B. D. Freeman, R. J. Spontek, Z. He, I. Pinnau; Science, 296 (2002) 519.

5. Z. He, I. Pinnau, A. Morisato; Desalination, 146 (2002) 11.

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6. T. C. Merkel, Z. He, I. Pinnau, B. D. Freeman, P. Meakin, A. J. Hill; Macromolecules, 36 (2003) 6844.

7. G. Golemme, A. Bruno, R. Manes, D. Muoio, Desalination, 200 (2006) 440.

8. M. Macchione, J. C. Jansen, G. De Luca, E. Tocci, M. Longeri, E. Drioli; Polymer, 48 (2007) 2619.

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Gas Separation IV – 6

Thursday July 17, 11:30 AM-12:00 PM, Kaua’i

Development and Characterization of PPO-based Emulsion Polymerized Mixed Matrix Membranes

Q. Wang, University of Ottawa, Ottawa, Ontario, Canada F. Sadeghi, Natural Resources Canada, Varennes, Quebec, Canada A. Tremblay, University of Ottawa, Ottawa, Ontario, Canada B. Kruczek (Speaker), University of Ottawa, Ottawa, Ontario, Canada - [email protected]

Molecular level combination between organic polymers and inorganic materials has been of interest for two decades and one of the major challenges in this field is achieving the compatibility between the organic and inorganic phases, which is critical for the synthesis of gas separation membranes.

In this presentation we will present a novel method for preparation of poly (2,6-dimethyl-1,4-phenylene oxide) (PPO)-based organic/inorganic membranes. Essentially, an inorganic precursor, aluminium hydroxonitrate, contained in a stable water-in-oil (W/O) emulsion was mixed with a polymer solution containing a second inorganic precursor, tetraethyl orthosilicate (TEOS). Inorganic polymerization occurred in or at the surface of the aqueous droplets of the W/O emulsion. Subsequently, thin films were prepared by a spin coating technique, and the resulting membranes were referred to as emulsion polymerized mixed matrix (EPMM) membranes. The size of the inorganic particles, which greatly affects their dispersion in a continues polymeric phase and determines whether or not phase separation occurs, was controlled by an ultrasonic energy input into the W/O emulsion. Such prepared membranes were characterized by EDX-Ray measurements, SEM, TGA and DSC analyses. The permeability and selectivity of the membranes were determined in air separation tests. The air separation tests also confirmed achieving compatibility between the phases. The effect of inorganic loading on the gas transport and physical properties of the PPO-based EPMM membranes will also be presented and discussed.

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Gas Separation IV – 7

Thursday July 17, 12:00 PM-12:30 PM, Kaua’i

Novel Semi-IPN Carbon Membranes Fabricated by a Low-Temperature Pyrolysis for C3H6/C3H8 Separation

M. Chng (Speaker), National University of Singapore, Singapore Y. Xiao, National University of Singapore, Singapore T. Chung, National University of Singapore, Singapore- [email protected] M. Toriida, Mitsui Chemicals, Inc., Japan S. Tamai, Mitsui Chemicals, Inc., Japan

One of the most important processes in petrochemical industries and petroleum refining is the separation of hydrocarbon mixtures with close boiling points, such as olefins and paraffins. At present, the separation of olefin and paraffin mixture is mostly carried out using low temperature distillation which requires enormous capital and large energy consumption. Membrane technology, which has the advantages of both low cost and reduced energy consumption as compared to the conventional separation processes, is potentially an attractive option, although it is the largest challenge to find suitable membrane materials with both high permeability and propylene/propane separation performance. Carbon membranes are chemically strong materials and have tailorable gas transport properties with high separation performance for gas pairs with very similar molecular dimensions such as C3H6/C3H8 through a molecular sieving mechanism. We will report a carbon membrane derived from Poly (aryl ether ketone). Interpenetrating polymer networks (IPNs) are a unique polymer blend, which is defined as a combination of two or more polymers in the form of network with at least one of which is crosslinked in the immediate presence of the other. IPNs successfully created polymeric nano-scale blends having new extraordinary properties. Carbon membranes display superior permeabilities- selectivity combination than polymeric membranes. Low pyrolysis temperature not only keeps the membrane flexibility and toughness, but also tends to avoid excessive closure of the main selective ultramicropores and hence increase the permeability and selectivity. As a result, the newly developed carbon membranes show a significantly enhanced olefin/paraffin separation performance due to the molecular sieving mechanism.

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EMS Barrer Prize – 1a

Thursday July 17, 8:15 AM-8:35 AM, Maui

My Membrane World

H. Strathmann (Speaker), Professor, Germany [email protected]

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EMS Barrer Prize – 1b

Thursday July 17, 8:35 AM-9:00 AM, Maui

Climbing Membranes and Membranes Operations

E. Drioli (Speaker), Institute on Membrane Technology of the Italian National Research Council, Rende, Italy - [email protected]

Membranes and membrane operations are today dominant technologies and their visibility in large part of the public is growing continuously. The situation was quite different not too many years ago. It is interesting and useful to revisit and rediscuss some of the problems and efforts which researchers and engineers had to overcome to reach their goals. The success of membrane science and membrane engineering are mainly related to the work of researchers able to face the basic problems related to the understanding the final morphology of dense and microporous membranes, their transport mechanism, and to develop new membrane operations, for molecular separation, chemical conversions, mass and energy transfer between different phases.

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EMS Barrer Prize – 2

Thursday July 17, 9:30 AM-9:55 AM, Maui

Membrane Separation of Nitrogen from High-Nitrogen Natural Gas: A Case Study from Membrane Synthesis to Commercial Deployment

R. Baker (Speaker), Membrane Technology and Research, Inc., USA - [email protected]

Fourteen percent of U.S. natural gas contains excess nitrogen, and cannot be sent to the national pipelines without treatment. Nitrogen is difficult to remove economically from methane, by any technology. Currently, the only process used on a large scale is cryogenic liquefaction and fractionation, but this technology requires economies of scale to be practical. Many owners of small gas fields cannot produce their gas for lack of suitable nitrogen separation technology.

This paper describes the development of selective membranes to treat natural gas containing high concentrations of nitrogen. Membranes selectively permeate either nitrogen or methane, the principal constituent of natural gas. Our work has shown that methane-selective membranes are generally preferable. We have produced membranes with high permeances and methane/nitrogen selectivities of approximately 3-3.5. This selectivity is modest, so commercial systems often require multi-stage or multi-step process designs. Despite the design complexity and compression requirements, multi-step/multi-stage membrane systems are the lowest cost nitrogen removal technology in many applications.

The development of this membrane technology to the commercial scale is described. To date, nine membrane-based systems for nitrogen removal during natural gas processing have been installed.

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EMS Barrer Prize – 3

Thursday July 17, 9:55 AM-10:20 AM, Maui

Molecular Simulations of Membrane Transport Processes

N. van der Vegt (Speaker), Max Planck Institute for Polymer Research, Mainz, Germany - [email protected]

In my talk I will discuss the use of molecular models in computer simulations of membrane transport processes. Detailed models, which include nearly all atomistic degrees of freedom, as well as less detailed, coarse-grained models, in which several covalently linked atoms are lumped together into a single interaction site, will be introduced. I will illustrate how these models can be used in multiscale polymer simulations spanning a wide range of time and length scales. These simulations permit describing relaxed (equilibrated) polymer morphologies on length scales up to 0.1-1 micrometer and in a second step to "zoom-in" down to Angstrom-scale resolution if atomistic details need to be further understood. I will emphasize future perspectives for membrane transport modeling by invoking this multiscale simulation approach. The examples discussed in my talk include thin-layer protective coatings on a solid substrate; predictive modeling of residual monomer diffusion in molten polystyrene with coarse-grained models; and solubility of bulky penetrant molecules in large-size simulation volumes of bulk polycarbonate calculated by means of fast-growth thermodynamic integration.

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EMS Barrer Prize – 4a

Thursday July 17, 10:20 AM-10:45 AM, Maui

Beyond Academic Research

G.-H. Koops (Speaker), GE Water & Process Technologies, Burlington, Ontario, Canada - [email protected]

This paper discusses some typical research questions that need to be answered to bring a new UF hollow fiber membrane for water filtration from development to commercial production.

Academic researchers typically report on relationships/effects between various components in the polymer solution and their membrane properties. Or study the effect of various spinning parameters on the membrane properties. Sometimes exotic polymers are synthesized, polymers are modified, or membranes are coated/post treated. Normally, all testing is done on small samples sizes, reproducibility is often neglected and costs are not at all a consideration. This makes academic research so much fun: there are no limitations, no CTQs!

In the industrial world this is quite different. Most new membrane introductions start off with the same kind of academic research, but with significant restrictions due to clear CTQs (Critical to Quality objectives). When this stage is passed and a new chemistry has been developed many more development stages follow before a new product makes it to the market. This paper addresses some challenges that are normally not studied by academics, but are critical for new product introductions. The challenges that will be addressed are: cost and material choice, chemical resistance testing, fiber breaks, fiber fatigue testing, scale up challenges, and performance testing.

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EMS Barrer Prize – 4b

Thursday July 17, 10:45 AM-11:10 AM, Maui

New Challenges in membrane preparation by phase inversion technique

A. Figoli (Speaker), ITM-CNR, Rende, Italy - [email protected]

The phase inversion technique allows producing both symmetric and asymmetric (porous and dense) membranes. Prof. Heiner Strathmann gave his strong contribution in this field, already in 1971, elaborating an original approach in which the process of membrane formation is shown in a simplified way as a line through the phase diagram [1-3]. Nowadays, the phase inversion technique still represents the most used procedure for membranes preparation that are usually employed in traditional separation processes from microfiltration/ ultrafiltration (porous membranes) to nanofiltration/reverse osmosis/pervaporation/gas separation (dense membranes). In this work, innovative polymeric membranes prepared by this technique are presented for potential food, environmental, pharmaceutical and chemical applications: a) a multilayer membrane film b) polymeric capsules and c) elastomeric asymmetric SBS membranes. a) The multilayer membrane was developed as an innovative antimicrobial food packaging film [4-5]. The ´intelligent´ film should recognize the presence of bacteria in the food and release an amount of antimicrobials suitable to inhibit bacterial growth and prevent spoilage. The multilayer film is made of three layers: 1) an outer dense layer to control the exchange rate of gases and vapour between the external and internal environment of the food packaging, 2) an intermediate adhesive tie-layer which has also the function of reservoir of antimicrobials, 3) a porous third layer, made by non-solvent induced phase inversion (NIPS), which is able to control the release of antimicrobials to the food in time. The release of antimicrobials can be adjusted changing the morphology of the porous layer that can be controlled varying the phase inversion process conditions. b) Polymeric capsules using a membrane process combined with the phase inversion technique (NIPS) was exploited [6]. This method can be identified as an integration between the traditional chemical capsule techniques (coacervation or phase inversion) and the mechanical capsule technique (pressure extrusion). It allows the formation of monodispersed polymer (modified polyetheretherketone) micro-capsules with different morphologies. The capsule morphology, porosity, size and shell thickness is easily adjusted changing the ingredient parameters such as polymer concentration, solvent and non solvent involved phases in the process. c) Novel asymmetric elastomeric SBS membranes were prepared by NIPS [7] which allows to taylor the morphology of the prepared membrane and to obtain a resistant membrane with a thin active layer in a single step. The success of the preparation of asymmetric elastomeric hydrophobic membranes leads to an easier membrane production at lower cost

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with respect to the composite membrane traditionally produced for pervaporation purposes.

References

1) H. Strathmann, P. Scheible, R.W. Baker ‘A rationale for the preparation of Loeb-Sourirajan Type Cellulose Acetate Membranes’, J. Appl. Polymer Science, 15 (1971) 811.

2) M.T. So, F.R. Eirich, H. Strathmann, R.W. Baker, ‘Preparation of anisotropic Loeb-Sourirajan Membranes’, Polymer Letters, 11 (1973) 201.

3) H. Strathmann, K.Kock, ‘The formation of mechanism of phase inversion membranes’, Desalination, 21 (1977) 241.

4) A. Figoli, E. Drioli, J.Jansen, M.Wessling, Film antimicrobico per prolungare la shelf-life, Rassegna dell Imballaggio, ISSN0033-9687, Nov. 2004, n.16, Year 25°.

5) J.C.Jansen, M.G.Buonomenna, A.Figoli, E.Drioli, Asymmetric membranes of modified poly(ether ether ketone) with an ultra-thin skin for gas and vapour separations, Journal of Membrane Science, 272 (2006) 188-197.

6) A. Figoli, G. De Luca, E. Longavita, E. Drioli, PEEKWC Capsules Prepared by Phase Inversion Technique: A Morphological and Dimensional Study, Separation Science and Technology 42 (2007) 2809-2827.

7) S.K. Sikdar, J.O. Burkle, B. K. Dutta, A. Figoli, E. Drioli, Method for fabrication of Elastomeric Asymmetric Membranes from Hydrophobic Polymers, US 11/598,840, filed 13 November 2006, publish in May 2008.

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EMS Barrer Prize – 5

Thursday July 17, 11:10 AM-11:35 AM, Maui

Considerations for Normal Flow Filtration: Fouling Models, Modules, and Systems

W. Kools (Speaker), Millipore Corporation, Billerica, Massachusetts, USA - [email protected]

Normal flow filtration processes in biotech processes are often batch processes run at constant pressure. To consider implementation of membrane processes at scale, several scales need to be considered: membrane performance, module performance and system performance.

On a membrane disk level, several fouling models can be used to describe the filtration behavior. Recently both in academic and commercial setting new combined models are introduced based on older models. A quick retrospective look and review of the newer models will be covered in this presentation.

Depending on the choices made during module design certain (in)efficiencies can be realized. Scaling factors should be included in defining required areas on a module level.

Finally, system considerations should be taken into account to make final designs.

Sensitivities on fouling model choice, module construction and system considerations are reviewed to identify implementation risks in sizing the required surface areas.

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EMS Barrer Prize – 6

Thursday July 17, 11:10 AM-11:35 AM, Maui

Dialysis Membranes – Continuous Improvements

B. Krause (Presenting), Gambro Dialysatoren GmbH, Hechingen, Germany - [email protected] M. Storr, Gambro Dialysatoren GmbH, Hechingen, Germany H. Göhl, Gambro Dialysatoren GmbH, Hechingen, Germany

Today, dialysis membranes are highly engineered separation devices and the manufacturing processes are fully automated. More than 150 million dialyzers having an average surface area of 1.8 m² are manufactured in 2007 world wide to treat patients suffering from chronic kidney failure. The continuous request for increased removal rates of uremic toxins and improved biocompatibility results in new membrane generations. New generations of dialyzers combine different separation principles and functions to increase separation performance and reduce treatment complexity for customers. In addition to the standard dialysis membranes more advanced High Cut-Off membranes have been developed that allow effective removal of substances in the molecular weight range between 25 and 50 kDa (middle molecular weight substances). This unique development gives access to a whole group of new extra-corporeal therapies. One example are patients with multiple myeloma suffering from elevated serum concentrations of monoclonal free light chains (FLCs), which can result in irreversible renal failure secondary to cast nephropathy. Because, elimination of these middle molecular weight compounds is limited by conventional dialysis membranes. We have investigated the removal of FLC using a novel High Cut-Off membrane. This membrane is characterized by a tailored pore size distribution and separation characteristics compared with conventional dialysis membranes.

In the first part new developments with dialysis membrane towards multifunctional and biological separation devices will be shown. In the second part in-vitro and in-vivo results using the High-Cut-Off membrane will be presented. Kappa and lambda FLC sieving coefficient and clearance were studied in-vitro in hemodialysis and hemodiafiltration mode. The ability of the membrane to reduce serum free light chain levels in-vivo was investigated in a clinical pilot study with patients who presented with dialysis dependent renal failure and multiple myeloma. With a kappa FLC sieving coefficient of 0.9 measured in human plasma the High Cut-Off membrane is effective in eliminating FLCs. Clearance rates of both FLCs were many times higher using the high cut-off membrane compared with a conventional High Flux dialysis membrane. In patients with multiple myeloma very large quantities of FLCs were removed with High Cut-Off dialysis. This resulted in post treatment reductions in serum FLC concentrations of between 45 and 81%. The removal rates of other

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therapy options have been modelled to confirm the advantages of the High-Cut-Off concept. Patients who achieved a sustained reduction in serum FLCs of greater than 65% became dialysis-independent following a mean treatment period of 21 days. Moreover, is has been shown that the mortality of the High Cut-Off membrane treated population decreases drastically.

Dialysis membrane research is path leading in the development of multi-functional synthetic and hybrid separation devices. High cut-off membranes exhibit a significant permeability for nephrotoxic free light chain proteins. High cut-off hemodialysis treatments allowed a rapid reduction of serum FLC concentrations in patients with multiple myeloma and dialysis dependent renal failure. Preliminary clinical data suggests that this treatment modality can improve renal outcomes in these patients.

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EMS Barrer Prize – 7

Thursday July 17, 9:30 AM-9:30 AM, Maui

On the Origin of the Overlimiting Current in Electrodialysis

M. Wessling (Speaker), University of Twente, Netherlands - [email protected]

The origin of the current flow above the limiting current density has been a puzzle ever since its discovery. Loss in membrane selectivity, gravitational convection, and in particular enhanced water splitting have been used as arguments to explain the occurrence of the overlimiting current. Yet another explaination is the emergence of electro-convection. This presentation reflects on these theories, but will present for the first time explicit experimental proof of the existance of electro-convection.

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Ultra- and Microfiltration II - Processes – 1 – Keynote

Thursday July 17, 8:15 AM-9:00 AM, Moloka’i

Membrane Applications in the Pulp and Paper Industry: New Developments and Case Studies

F. Lipnizki (Presenting), Alfa Laval Product Centre Membranes, Soborg, Denmark - [email protected] T. Persson, Lund University, Lund, Sweden A.-S. Jönsson, Lund University, Lund, Sweden

Every year, 100,000 tons of dissolved hemicelluloses are discharge unused with wastewater from thermomechanical pulp mills around the world. Isolation of these hemicelluloses from the wastewater would not only reduce the treatment costs for the pulp mills but would also provide an excellent raw material for high value applications such as oxygen barriers in food packaging. The isolation of the hemicelluloses can be combined with polishing of the wastewater by using different filtration processes. The initial step in this combination is either a drum filter or a microfiltration treatment to remove solid residues from the wastewater followed by ultrafiltration to concentrate the hemicelluloses. The permeate from the ultrafiltration can then be further polished by reverse osmosis before recycling. The focus of this paper is on the optimisation of the ultrafiltration step concentrating on the membrane selection and its impact on the process economics. The membrane selection includes the newly developed commercial UFX5 pHt membrane (Alfa Laval, Denmark) based on hydrophilised polyethersulfone. The feed studied in this paper is process water from the thermomechanical pulp mill Stora Enso Kvarnsveden (Sweden). The temperature of this process stream is 75°C. To reduce the need for cooling and preserve the energy, temperature tolerance is an important membrane selection parameter. Further, since the process water contains resin and lignin, which tend to foul membranes, the hydrophilicity of the membrane is another important selection parameter. Based on this, five membranes with molecular weight cut- offs (MWCOs) between 1 - 10 kD were pre-selected: (1) a hydrophilised fluoro polymer membrane ETNA10PP, MWCO: 10 kD, (2) a hydrophilised fluoro polymer membrane ETNA01PP, MWCO: 1 kD, (3) a hydrophilised polyethersulfone membrane UFX5 pHt, MWCO: 5 kD (all Alfa Laval, Denmark), (4) a regenerated cellulose membrane UC005, MWCO: 5 kD, and (5) a polyethersulfone membrane UP005, MWCO: 5 kD (all Microdyn-Nadir, Germany). The ETNA10PP, ETNA01PP, and UC005 are limited to a temperature of 60/55°C and to a pH range of 1 to 11, whereas the UP005 and UFX5pHt can be operated up to 75°C and in a pH range from 1 to 14/13. In the initial study, a small flat test module was used to study the pure water fluxes and the fouling behaviour of the membranes related to octanoic acid, a fouling substance which represents a significant number of small hydrophobic substances. Based on this,

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ETNA01PP, ETNA10PP, and UFX5pHt were selected for further experiments in 2.5 spiral wound modules using process water from Kvarnsveden pulp mill. In these experiments, among others the flux decline with increasing concentration of hemicelluloses at different transmembrane pressures and cross-flow velocities as well as the retention of hemicelluloses under these conditions were studied. The experimental results of ETNA10PP, ETNA01PP and UFX5pHt were then used as basis for the development of a full-scale system to treat a feed stream of 100 m3/h with an initial feed temperature of 60/75ºC. Both investment and operating costs were analysed as well as the impact of retention and operating conditions on the ultrafiltration process. It was revealed that operating temperature and membrane selection/retention had an impact on both the investment and operating costs. In conclusion, the results show that ultrafiltration is an attractive process unit in the hemicelluloses isolation process.

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Ultra- and Microfiltration II - Processes – 2

Thursday July 17, 8:15 AM-9:00 AM, Moloka’i

PAA and Thiol Functionalized MF/UF Membranes for Surfactant Separation and High Value Metal Capture: Experimental Results and Modeling

A. Ladhe (Speaker), University of Kentucky, Lexington, Kentucky, USA - [email protected] P. Frailie, University of Kentucky, Lexington, Kentucky, USA D. Bhattacharyya, University of Kentucky, Lexington, Kentucky, USA

Modification of microfiltration membranes with desired functional groups and their subsequent applications for selective separations is receiving increasing attention. The desired membrane functionalization can be achieved through chemical modification, graft copolymerization, covalent binding, layer by layer attachment of polyelectrolytes etc. In this study two types of functionalized microfiltration membranes were studied for surfactant separation from hydrophobic solvent and high value metal capture from aqueous solutions.

Commercially available hydrophilized polyvinylidene fluoride (PVDF) MF membrane (pore diameter 0.45 micrometer) was functionalized with poly(acrylic acid) (PAA) with subsequent partial cross-linking by ethylene glycol at 110 degree celcius. Ethoxylated nonionic surfactant solution in siloxane based solvent was permeated through this membrane to study surfactant separation. PAA is known to form a complex with ethoxylated nonionic surfactants in aqueous phase through hydrogen bonding between carboxyl groups of PAA and ethylene oxide groups of the surfactants. Hydrophobic attraction between alkyl chain of the surfactants and PAA also contributes towards the interaction. The role of ethylene oxide content of surfactant molecule on the surfactant separation was studied and it was observed that extent of separation increased by 20 fold when ethylene oxide groups per surfactant molecule increased from 3 to 8. The pH dependence of the membrane permeability due to ionization changes of the functionalized PAA inside membrane pore was also studied. The membrane flux decreased from 60E-4 to 2E-4 cm3/cm2-s (applied pressure = 2 bar) with increasing pH from 1 to 6. The pH sensitivity of the surfactant-PAA complex was useful for membrane regeneration. The successful regeneration and reuse of the membrane is attractive in terms of process development for surfactant based cleaning operations.

Another way of membrane functionalization is to incorporate solid inorganic particles with desired functional groups inside membrane matrix. These types of mixed matrix membranes (MMMs) have been studied extensively for gas separations. Preparation of MMM by phase inversion method in order to have highly interconnected porous UF type membranes opens new domain for

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convective flow liquid phase applications. Silica particle functionalization by silane chemistry is well studied in the literature. In this particular case, silica particles were functionalized with 3-mercaptopropylsilane in order to obtain free surface thiol groups and incorporated into polysulfone matrix. Thiol groups strongly interact with various metals like Au, Hg, Ag etc which may be applied advantageously in various applications like water treatment and high value metal capture processes. In order to demonstrate applicability of the MMMs, silver ion is selected as the target metal ion for separation from its aqueous silver nitrate solutions. The silica-polysulfone MMMs were characterized by SEM and permeability measurements. It was observed that membrane permeability increased with increasing silica loading (weight fraction) in the membrane. The effect of silica properties like particle size, specific surface area, and porous/nonporous morphology on the silver ion capture capacity was studied. Typical silver capture capacity was in the range of 1.5 to 2 mmole per gram of silica (20E-4 mmole per square meter of particles). Dynamics of the silver capture process were studied by performing experiments at various applied transmembrane pressure. Initially, the dynamic silver capture capacity decreased from 70% to 40% of equilibrium capacity with increasing membrane flux and became flux independent thereafter. It was also demonstrated that the membrane can capture silver selectively in presence of significant concentration of other metal ions like calcium. One dimensional unsteady state model with overall volumetric mass transfer coefficient was developed and solved to predict silver ion concentration in liquid phase and silica phase along the membrane thickness at varying time. The breakthrough curve data predicted using model solution is comparable with the experimental observations. Furthermore, fundamental silver ion � thiol interaction was studied by QCM (Quartz Crystal Microbalance) technique.

Peter Frailie was supported by the NSF-REU program.

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Ultra- and Microfiltration II - Processes – 3

Thursday July 17, 10:00 AM-10:30 AM, Moloka’i

Assuring Biodiesel Quality via Selective Membrane Filtration

M. Gutierrez-Padilla (Speaker), University of Colorado, Boulder, Colorado, USA J. Downs, University of Colorado, Boulder, Colorado, USA J. Pellegrino, University of Colorado, Boulder, Colorado, USA - [email protected] J. Bzdek, Symbios Technologies, LLC, Fort Collins, Colorado, USA

Biodiesel is produced by transesterification/esterification of lipids derived from vegetable oils and waste fats. As a transportation fuel, biodiesel has some desirable end-use attributes (including particulate emissions) versus petrodiesel and thermochemically produced "green" diesel, which support its continued use as part of the "sustainable" transportation fuel infrastructure. Nonetheless, commercial experience has shown infrequent incidents of formation of a cloudy-haze, and vehicle filter clogging problems, presumably due to trace contaminant species, which need to be resolved. There may be several causes for each of these quality-related events, and due to the variable feedstock sources, a broad- based processing approach merits consideration. We have studied crossflow membrane filtration of biodiesel with a variety of membrane structures and material chemistries. Besides obtaining some process design-related figures-of-merit, for example, the membrane permeances versus applied transmembrane pressure, we assayed the streams using the modified ASTM 6217 test (aka the "cold soak" test), which is used as a quality control metric for filterability. We will report results from several membranes, icluding a polyethylene microfiltration membrane; several ultrafiltration membranes made from polyethersulfone and polyvinylidene fluoride, and a solvent resistant nanofiltration membrane. The filtration process was performed continuously with a retentate recycle until permeate recoveries of 30 to 75% were obtained. (NB. Commercial processing can be done to much higher recovery, ~98-99%, using a feed-and-bleed design.) The main effect we studied was the transmembrane pressure, which was in the range of 34 to 207 kPa (5 to 30 psi). Membrane cleaning for some membranes was performed after the filtration tests by running methanol or ethanol across the top of the membrane. These membranes could be reused after the cleaning. Permeances in the range of 1.3x10-7 to 6x10-8 m/s/kPa could be consistently obtained with some of the UF membranes. The hazy feedstock and the retentate from all trials failed the cold soak test, but the ultrafiltration permeates passed it. The microfiltration membrane was not fully acceptable in assuring that the permeate passed the cold soak test. In addition, we analyzed our samples using GCMS to quantify the fatty acid methyl esters (FAME) profile in the original feedstock (soybean oil-based) and permeate. We found that the filtration process

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did not perceptibly change that profile. To date we have not been able to identify the contaminants.

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Ultra- and Microfiltration II - Processes – 4

Thursday July 17, 10:30 AM-11:00 AM, Moloka’i

High Oxidative Resistant PVDF UF Membrane for Metal-CMP Wastewater Treatment

S. Shiki (Speaker), ASAHI KASEI CHEMICALS, Shizuoka, Japan - [email protected] G. Furumoto, ASAHI KASEI CHEMICALS, Shizuoka, Japan

We developed a novel ultrafiltration (UF) hollow fiber membrane made of polyvinylidenfluoride (PVDF) suitable for wastewater treatment including oxidants and organic solutes. In this paper, we describe the membrane characteristics and an example of filtration by using semiconductor industry wastewater including turbidities and oxidative chemicals.

Recently, as it becomes high integration of semiconductor, the metal chemical mechanical polishing (metal-CMP) process is spreading in the semiconductor industry. This process puts out an oxidative wastewater including the polishing slurry, and it is necessary to treat this wastewater. Conventionally, UF membranes have been used for semiconductor industry wastewater, but for the metal-CMP wastewater, the polymeric membranes are damaged by oxidants and that leads to membrane breakage.

Asahi Kasei Chemicals is the pioneer on developing PVDF microfiltration (MF) hollow fiber membrane, and because of its high mechanical strength and chemical resistance, it has been used for many applications, especially for water purification and membrane bioreactor (MBR). However, it is difficult to use MF membrane for metal-CMP wastewater treatment because the slurry with a size of about 10 to 100 nm, pass through the MF membrane pores.

The necessity of UF membrane for metal-CMP wastewater treatment has been increasing, however, our existing UF membrane could not stably be used in that application due to their low oxidant resistance. Therefore we developed the epoch-making PVDF UF hollow fiber membrane. And also, there were no PVDF UF hollow fiber membranes with high durability and good permeability because it was difficult to make PVDF UF membrane due to its low processability.

Our new PVDF UF membrane has high permeability, sufficient mechanical strength and high chemical resistance, especially to oxidants, compared to our conventional polymeric membranes, such as those made of polysulfone and polyacrylonitrile. In addition, we also found that chemical resistance of our novel PVDF UF membrane was superior to other PVDF membranes and that the difference in chemical resistance among PVDF membranes was derived from the

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membrane structures, which would be determined by their different manufacturing processes.

The result of long term filtration test, using semiconductor plant metal-CMP wastewater, showed that the permeated water quality was good, for example Si: 100ppm (raw water) to 5 ppm (filtrate); TOC: 20 ppm to 0.4 ppm and filtration was stable for over 5 months.

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Ultra- and Microfiltration II - Processes – 5

Thursday July 17, 11:00 AM-11:30 AM, Moloka’i

Hygienic Barrier Efficiency of a Coupled Coagulation / Flocculation and Ceramic Microfiltration System for Potable Water Production

T. Meyn (Speaker), Norwegian University of Science and Technology, Trondheim, Norway - [email protected] A. König, Technical University Berlin, Berlin, Germany T. Leiknes, Norwegian University of Science and Technology, Trondheim, Norway

Due to climatic and geographical conditions, Norway has an abundance of water resources and about 90% of drinking water supplies are from surface water sources, mostly lakes with very low turbidity. In general, the drinking water sources are characterized by high concentrations of natural organic matter (NOM), low pH, low alkalinity and low turbidity. Typical values are; colour of 30-80 mg Pt/l, TOC 3-6 mg C/l, COD 4-8 mg Mn/l, turbidity < 1 NTU, alkalinity < 0,5 meq/l and hardness < 5 mg Ca/l. The removal of NOM is a primary treatment concern since coloured water is unattractive to consumers, results in colouring of clothes during washing, can cause odour and taste, increases corrosion and biofilm growth in the distribution network, and is a precursor to the formation of disinfection by-products (DBP) when water is disinfected. Coagulation / flocculation coupled with a MF ceramic membrane filtration plant is a promising alternative membrane process for the removal of NOM to produce potable water. National regulations for drinking water production requires minimum of two hygienic barriers and the object of this study has been to assess the hygienic barrier efficiency of this treatment alternative.

Bacteria and viruses in drinking water can cause diseases among consumers. These viruses belong to the group of adenoviruses, astroviruses, enteroviruses, hepatitis-A and hepatitis-E viruses, noroviruses and rotaviruses. These human pathogenic viruses mostly reproduce themselves in the gastrointestinal tract and get together with the faeces in big amounts into wastewater and the environment. This especially becomes important because viruses can be regularly found in the effluent of conventional treatment plants and the fact that the portion of treated waste water in rivers can be high.

The MF ceramic membrane filtration unit used in this study is based on dead-end operation of multi-bore tubular membranes with a pore size of 0,1 µm. The filtration pilot plant consists of three trains with an integrated flocculation step. The membranes were operated at a flux of 140 LMH. Two different coagulation agents, polyaluminium chloride and iron chloride were tested. The virus and bacteria removal capacity was determined by using MS2-bacteriophage and Escherichia coli respectively. Possible virus inactivation by the applied

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coagulants was also investigated. The virus removal was examined in dependence on the operational parameters of the coagulation step: pH-value, coagulant dose and type and flocculator setup.

Without any flocculation nearly all viruses passed through the microfiltration membrane. Even at low doses of coagulant the removal was improved significantly. For example, at iron concentrations of 8 mg / L and alum concentrations of 4 mg / L, virus concentrations of d 1 plaque forming units per millilitre (pfu/mL) were observed in the permeate, depending on the operating conditions and starting with a virus concentrations of 107 to 108 pfu/mL in the raw water. More detailed results will be shown in the presentation.

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Ultra- and Microfiltration II - Processes - 6

Thursday July 17, 11:30 AM-12:00 PM, Moloka’i

Pioneering Explorations of Rooting Causes for Morphology and Performance Differences in Hollow Fiber Kidney Dialysis Membranes Spun From Linear and Hyperbranched Polyethersulfone

Q. Yang (Speaker), National University of Singapore, Singapore T. Chung, National University of Singapore, Singapore - [email protected] M. Weber, BASF Aktiengesellschaft V. Warzelhan, BASF Aktiengesellschaft

The adoption of conventional polyethersulfone (PES) material with linear structure for kidney dialysis membrane application has attracted intensive attention due to its excellent stability under sterilization, superior bio-compatibility after the polyvinylpyrrolidone (PVP) modification, and minimal degradation in membrane performance over extended period of time. On the other hand, polymers with highly branched structure have also witnessed gaining interests during the past decade due to their large number of functional groups and high surface reactivity in contrast to their linear analogues. Although much progress has been achieved in the structural understanding and the synthesis of hyperbranched polymers, fundamental understanding and especially industry application of these hyperbranched polymers are still in infancy. In addition, there were few studies conducted to systematically compare hyperbranched polymers properties with their linear analogues, but not to speak of identifying the differences between hollow fiber membranes spun with the linear and hyperbranched counterparts.

First of all in this NUS-BASF joint research program, the science and engineering of hollow fiber membrane formation by a dry-jet wet-spinning technique was investigated in-depth in order to identify a membrane with desirable structure, suitable pore size and pore size distribution for kidney dialysis applications. The dual-bath coagulation technique has been employed for the first time in this study for fabricating kidney dialysis membranes: with a weak coagulant isopropanol (IPA) serving as the first external coagulation bath while water as the second bath, the as-spun membrane can achieve a tight inner selective skin and loose outer supporting layer structure. This is a desirable membrane structure for removing low and middle molecular weight uremic toxins such as uric acid, urea, creatinine, inulin and beta2-microglobulin but retaining proteins molecules during hemodialysis.

In addition, we have identified that the addition of PVP into the polymer dope (both linear and hyperbranched PES) during the hollow fiber membrane spinning could not only provide a macrovoid-free and completely sponge-like structure but

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also improve the resultant membrane’s hemocompatibility. After being treated in 8000 ppm NaOCl solution for 1 day, fibers show larger pore sizes and porosity in both inner and outer surfaces, and thinner inner and outer layers than their as-spun counterparts. Based on SEM observations and solute rejection performance, the further heat treated fibers in an aqueous solution is found to be an effective way to fine tune membranes morphology and molecular weight cut-off (MWCO) for kidney dialysis application.

Last but not the least, comprehensive comparisons of the linear and hyperbranched PES, especially their as-spun hollow fiber kidney dialysis membranes were conducted based on their physical, chemical, thermal and rheological properties. The most significant differences between the hyperbranched PES material and its linear analogue were identified by its higher molecular weight, wider molecular weight distribution and a much more compact structure. The molecular characteristics of hyperbranched PES led its as-spun membrane with smaller pores, narrower pore size distribution, and a smaller MWCO. In addition, hyperbranched PES bound stronger with the additive PVP and their blend displayed a lower coefficient of thermal expansion (42.16μm/°C) than that for linear PES (89.08μm/°C). Both factors resulted in a less effectiveness of PVP leaching by the NaOCl solution and hot water. A higher water temperature was required to tailor the as-spun hyperbranched PES hollow fibers with the pore size and pore size distribution suitable for kidney dialysis application. To our knowledge, this is the first work to reveal the morphologies and solute separation performances differences between hyperbranched- and linear- PES made membranes based on the comprehensive explorations and fundamental understandings of these two polymer analogues properties.

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Ultra- and Microfiltration II - Processes – 7

Thursday July 17, 12:00 PM-12:30 PM, Moloka’i

Pressurized Porous Nanocrystalline Silicon Membranes Exhibit High Permeability to Water and Gas

T. Gaborski (Speaker), University of Rochester, Rochester, New York, USA D. Fang, University of Rochester, Rochester, New York, USA C. Striemer, University of Rochester, Rochester, New York, USA M. Kavalenka, University of Rochester, Rochester, New York, USA J. Snyder, University of Rochester, Rochester, New York, USA M. Hoffman, University of Rochester, Rochester, New York, USA J. DesOrmeaux, SiMPore Inc., West Henrietta, New York, USA P. Fauchet, University of Rochester, Rochester, New York, USA J. McGrath, University of Rochester, Rochester, New York, USA - [email protected]

We recently introduced porous nanocrystalline silicon (pnc-Si) as a molecularly thin membrane material capable of size and charged based separation of proteins and other nanometer-sized solutes (Striemer et al. Nature, 2007). The membranes can be produced in massive arrays with membranes freely suspended over millimeter support spacings. Mechanical tests indicate surprising strength with failure at or above 15 psi with no fatigue prior to rupture. Average membrane pore sizes can be tuned between 5 nm to 100 nm with porosities between 0.1-10%.

The structure of pnc-Si membranes suggests that they should display extraordinary permeability to water and gas under pressure. To test this prediction, we formatted membranes for easy assembly into gas pressure cells and centrifuge tube inserts. For membranes with mean pore sizes ~ 20 nm and porosities ~ 2%, we measured hydraulic permeabilities of nearly 2 x 10-8 m/(s-Pa) and air permeability in excess of 5 x 10-5 (m/s-Pa). These values are at least tenfold higher than the permeability values for commercial ultrafiltration membranes measured in side-by-side comparisons. The permeabilities to air and water are also more than one order higher than literature values for carbon nanotube/polymer composite membranes. Because pores can be directly imaged in electron microscopy, we employ known pore sizes and distributions to test existing theories for gas and water permeability of ultrathin membranes (Tong et. al. Nano Letters, 2004). For both water and air, we find that the existing theories are predictive of the flow rates we measure through specific membranes. Interestingly, native pnc-Si membranes are impermeable to water if one side of the membrane is left dry, highlighting the significance of surface tension and high curvature for liquid flow through nanoporous membranes.

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Drinking and Wastewater Applications IV – 1 – Keynote

Thursday July 17, 8:15 AM-9:00 AM, Honolulu/Kahuku

Optimization of Bubbly Flow in Flat Sheet Membrane Modules

H. Prieske (Speaker), Technische Universität Berlin, Berlin, Germany A. Drews, Technische Universität Berlin, Berlin Germany M. Kraume, Technische Universität Berlin, Berlin, Germany - [email protected]

Introduction and Aim

In the operation of membrane bioreactors for wastewater treatment, continuous or intermittent air scour is applied to reduce cake layers and thus to minimise fouling. Optimisation of module design and operating conditions (e.g., distance between flat sheet membranes, crossflow velocity, aeration intensity, etc.) requires knowledge of the most suited hydrodynamic conditions for the filtration task. Especially the circulation velocity which is induced by the bubble movement is of importance. However, many fundamentals of this gas/liquid flow are still unknown and difficult to access experimentally. While a number of studies on the influence of bubble motion have been carried out for hollow fibre membranes, much less work has been published on bubbly flow in flat sheet modules. Thus, the aim of this study is the fundamental investigation of gas/liquid flow between flat plates and the corresponding wall shear stresses. Special attention is drawn on the movement of differently sized single bubbles in the gap between plates. Using experimental and numerical methods, the optimum bubble size and air flow rate for fouling control in relation to the respective plate distance will be determined.

Methods

The examined module was operated in airlift loop configuration with a circulating flow induced by the aeration of the flat sheets (riser section) whereas the outer area was not aerated and represented the downcomer section of the total airlift. Experiments were carried out with water and air in a quasi two-dimensional MBR model with 2.1 m height, 1.2 m width and 0.1 m depth. Particle Image Velocimetry and an impeller anemometer were applied to measure the liquid velocities. Bubble distributions were optically analyzed by video imaging through the transparent walls of the tank. The movement of differently sized air bubbles rising in stagnant water between differently spaced flat plates was recorded using a highspeed camera. From this, the terminal bubble rise velocity was determined which together with the observed bubble shape serves as a validation for the numerical investigations. The velocity profile between the membrane plates was calculated by a CFD code (CFX) based on the Eulerian-Eulerian approach for two-phase flow. Additionally the flow field and especially the wall shear stresses

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in the vicinity of the rising bubbles were simulated with CFD (Fluent) in combination with the volume of fluid (VOF) method (constant surface tension, time step 10-6 - 10-4 s). All these numerical simulations were also used to perform parameter studies by varying geometrical values or operating conditions (e.g. channel width, bubble diameter) studying their influence on the wall shear stresses in order to minimise fouling.

Results For the circulating flow the measured and simulated liquid velocities showed good agreement. So CFD simulations are an appropriate tool for the optimisation of module and filtration tank geometry. Furthermore typical problems in the operation of flat sheet membrane modules became evident such as insufficient aerated gaps in the outer region of the module. In practice this will lead to an accelerated fouling in this area and a subsequent permeability reduction of the total module. By an improved design of the gas sparger a more homogeneous bubble distribution in the membrane module and an accelerated circulation was achieved. The rise velocity of bubbles ascending between differently spaced plates showed that small bubbles move like in an unconfined liquid. Above a certain diameter, however, which is smaller for narrowly spaced walls, bubbles briefly slow down as the deceleration effect caused by the walls becomes dominant. With further increased size, the presence of the walls drastically changes the bubble shape: they become elongated and flat cap bubbles. Due to the thus decreased projected area, bubbles with a diameter above 10 mm overcome the deceleration effect and even achieve higher rise velocities between plates than in unconfined environments. Although this acceleration is independent of channel width, the plate distance influences the maximum possible stable bubble size. Even small bubbles disrupt due to the higher shear in narrow channels. In order to optimize bubble size and wall distance for fouling control, the shear rates must be known. From the CFD simulations the maximum wall shear stresses have been deduced. As expected, highest shear can be achieved for narrow channels which, however, would become clogged too easily in sludge systems. For practical applications an optimum bubble size and membrane gap of both 5 mm is suggested.

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Drinking and Wastewater Applications IV – 2

Thursday July 17, 9:30 AM-10:00 AM, Honolulu/Kahuku

Removal of Organic Micropollutants with NF/RO Membranes: Derivation and Validation of a Rejection Model

A. Verliefde (Speaker), Delft University of Technology, Delft, The Netherlands - [email protected]

E. Cornelissen, Kiwa Water Research, Nieuwegein, The Netherlands B. Heijman, Kiwa Water Research, Nieuwegein, The Netherlands G. Amy, UNESCO-IHE, Delft, The Netherlands B. Van der Bruggen, University of Leuven, Leuven, Belgium H. van Dijk, Delft University of Technology, Delft, The Netherlands

Drinking water utilities in Europe are facing a growing presence of organic micropollutants in the water sources. Not only surface waters, but also ground waters are increasingly contaminated with a wide range of organic pollutants, such as pesticides, hormones, pharmaceutically active compounds and other problematical substances, e.g. the fuel additive MTBE or the potent carcinogenic NDMA. Even though these substances often only occur at low concentrations, removal in the drinking water treatment is still desirable, since health effects related to consumption of drinking water containing traces of these substances are yet unknown. Nanofiltration (NF) and reverse osmosis (RO) as water treatment processes are often considered as effective remediation techniques for trace organic pollutants, since the molecular weight cut-off values of the membranes are often in the range of the molecular weights of the organic micropollutants. In some cases, however, organic solutes are still detected in the permeate of NF/RO installations, indicating incomplete removal.

An integrated understanding of trace organic rejection mechanisms has begun to emerge, which now includes the perspective of solute-membrane interactions such as steric, electrostatic, and hydrophobic (solute-membrane affinity) effects. These solute-membrane interactions are influenced by solute and membrane properties, process conditions and feed water composition.

In this research, the effect of solute-membrane interactions on trace organics transport through NF/RO membranes was studied and translated into mathematical models. By carrying out selected rejection tests with model organic solutes and different membranes on single 4-inch NF/RO membrane elements, the effects of the different solute-membrane interactions on rejection could be determined. With this knowledge, a rejection model for uncharged solutes was developed, based on a convection- diffusion model, but extended with parameters accounting for membrane-solute affinity (hydrophobic interactions). Secondly, the influence of both solute and membrane charge (and the influence

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of feed water ionic strength) on rejection was also investigated and incorporated into the mathematical model. Results suggest that, in contrast to the rejection of inorganic solutes, the Donnan-exclusion mechanism does not seem to play a role in the rejection of charged organic solutes. The models for uncharged and charged solutes were then combined into a general rejection model for organic solutes in aqueous solutions. Using mass balances, this general rejection model was then extended to a mathematical expression for the rejection of organic solutes in full-scale installations.

The full-scale rejection model was tested and validated by spiking a cocktail of 25 pharmaceutically active compounds and pesticides on a 2 stage pilot installation. The pilot scale installation contained 18 4-inch membrane elements (12 in the first stage, 6 in the second stage) and was operated during 2 different runs at 75% and 83% recovery. During these runs, permeate samples of the different stages and of the first and last membrane element were collected and analysed for pharmaceuticals and pesticides. This way, rejection values at different recoveries could be determined and compared to the modelled rejection values. The modelled rejections seemed to correspond to the measured full-scale rejection values at different recoveries quite well.

Results obtained in this study may prove to be very useful for future applications of membrane filtration for potable water purposes. The derived models may provide an a priori evaluation of the performance of a full-scale membrane filtration plant: based on selected parameters of solute and membrane, the rejection of an organic solute with a full-scale NF/RO plant can be estimated.

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Drinking and Wastewater Applications IV – 3

Thursday July 17, 10:00 AM-10:30 AM, Honolulu/Kahuku

Anaerobic Membrane Bioreactor (AnMBR) for Landfill Leachate Treatment and Removal of Hormones

A. Do, University of South Florida, Tampa, Florida, USA A. Prieto, University of South Florida, Tampa, Florida, USA D. Yeh (Speaker), University of South Florida, Tampa, Florida, USA - [email protected]

To date, the majority of the studies on trace pharmaceuticals and endocrine disrupting compounds (EDCs) have focused on their fate in sewage treatment plants. However, EDCs can enter the landfill via several routes, including household solid waste and sludge from wastewater treatment plants. Increasingly, in light of the ineffectiveness of conventional wastewater treatment systems to completely remove these contaminants, the public is instructed to dispose of PPCP in household trash in the US. In a recent survey conducted in the UK, two-thirds of the subjects disposed of unwanted or expired mediation through household trash. With the maturing of the Baby Boom Generation and our society's increasing reliance on mediation, there is good reason to anticipate that states with high populations of the elderly, such as Florida, will receive high loadings of EDCs to landfills in years to come. Even if the EDCs are disposed in bags or containers, it is likely that they will be released once they enter the general trash stream, either through mechanical compaction and breakage in the garbage trucks or at the landfill. Additionally, containers can lose integrity in the landfill from degradation, thereby enabling the contents to enter the general contents of the landfill. In short, landfills can serve as a long-term source of EDCs for soil and groundwater contamination.

To prevent environmental contamination and to comply with state and local regulations, an effective method is needed for treating and removing xenobiotic compounds from landfill leachate. Landfill leachates are among the most difficult waste streams to treat, as they typically contain high concentrations of dissolved and colloidal organics (much of which may be recalcitrant and hard to degrade), inorganics (e.g., ammonium), heavy metals (e.g., arsenic, mercury, cadmium, copper, and xenobiotic organic pollutants (e.g., chlorinated organics). Further, constituents of the effluent can be toxic or inhibitory to many conventional biological treatment processes. Although there is a growing trend to operate landfills themselves as biological reactors, young landfills will rely most heavily on an external leachate treatment system while the biological activity establishes within the landfill itself.

The membrane bioreactor (MBR), in which biological waste treatment and membrane separation (typically MF or UF) are synergistically-coupled, is a

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technology that has gained growing popularity in the past fifteen years. To date, MBRs are used primarily for the treatment of municipal and some industrial wastewaters. While MBRs have been used with success for the treatment of landfill leachate in Europe (more than 30 installations in Europe during the 1990's), there has been relatively few applications of such in the United States, with only one full-scale plant commissioned in North America.

The objective of the present study is the development of an anaerobic MBR technology to treat leachate. In the initial phase of the current research, a laboratory-scale system was developed to treat simulated young landfill leachate with comparable COD, ammonium, inorganic species, etc. A 5L anaerobic membrane bioreactor is equipped with temperature and pH control, sensors and automatic logging of bioreactor (total gas, methane, temperature, pH, ORP, ammonium) and membrane (TMP and permeate flux) performance data. The reactor includes dual external crossflow membrane system (with CIP) for parallel comparison of membrane materials and operating conditions. We are testing PVDF UF membranes (with and without anti-fouling coating) provided for this study by Membrane Technology Research, Inc. (MTR, Menlo Park, CA). The reactor was started with anaerobic digestion sludge from a local WWTP.

The target EDC is 17beta-estradiol (E2), a prevalent female hormone used for contraceptives and hormone replacement therapy. Due to the nature of packaging and widespread use in households, the entry of E2 into landfills is highly likely. E2 has also been measured in leachate. The quantification of E2 in this project is performed by the use of solid-phase microextraction (SPME) with GC/MS. To facilitate E2 retention and removal by the AnMBR, as well as to control membrane fouling, we added powder activated carbon (PAC) to the reactor. Separate batch assays were conducted to determine the anaerobic biodegradability of E2 as well as to measure the respective distribution coefficients of E2 to PAC and sludge biomass. The biodegradation kinetics and distribution coefficients were used to guide reactor operational conditions. In this presentation, we will report on the reactor design, initial testings and startup operation of the anaerobic MBR.

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Drinking and Wastewater Applications IV – 4

Thursday July 17, 10:30 AM-11:00 AM, Honolulu/Kahuku

Comparison of Multi-Parameter Optimization Strategies for the Development of Nanofiltration Membranes for Salt and Micropollutants Removal

A. Cano-Odena (Speaker), Katholieke Universiteit Leuven, Leuven, Belgium P. Vandezande, Katholieke Universiteit Leuven, Leuven, Belgium I. Cools, Katholieke Universiteit Leuven, Leuven, Belgium K. Vanderschoot, Katholieke Universiteit Leuven, Leuven, Belgium K. De Grave, Katholieke Universiteit Leuven, Leuven, Belgium J. Ramon, Katholieke Universiteit Leuven, Leuven, Belgium L. De Raedt, Katholieke Universiteit Leuven, Leuven, Belgium I. Vankelecom, Katholieke Universiteit Leuven, Leuven, Belgium - [email protected]

Introduction

The currently and since years growing water demand worldwide, together with new and more strict regulations for potable and waste water levels, lead to the need of better cleaning technologies to decrease the concentration of micropollutants (pharmaceutical active compounds, endocrine disrupting compounds,etc) in water streams, whose properties affect environmental and human health. Membrane-based technologies (nanofiltration and reverse osmosis) seem better positioned to remove trace contaminants than conventional techniques.[1]

There are several parameters involved in membrane synthesis, including compositional and non-compositional. Multi-parameter optimization strategies are extremely useful in membrane technology to minimize time and material consumption to develop better performing membranes. Combinatorial synthesis refers to change in the nature of the compositional parameters. High-throughput experimentation(HT) enables rapid and accurate collection of large data-sets essential for the implementation of combinatorial synthesis together with miniaturization (cost, waste reduction).[2] Combinatorial techniques have been used already in the pharmaceutical industry, material development and catalysis leading to successful implementation and great revolutionary impact. Its combination with membrane technology is still incipient but promising to direct membrane synthesis towards better separation properties (selectivity) of the targeted compounds combined with useful fluxes.

Objectives

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Optimize polymeric membranes for salt and micropollutants removal in aqueous streams. Explore compositional and non-compositional parameters of membrane synthesis in such membrane optimization strategies. Compare different multi-parameter optimization strategies and machine learning methods to optimize membrane performance (permeability, selectivity) for these applications. Evaluate which one leads to faster convergence and better results.

Methods

Polymeric NF membranes will be prepared via phase inversion. Their performance will be evaluated to retain ibuprofen from water. Ibuprofen is selected as one of the smallest molecules from relevant micropollutants currently present in drinking water. Its succesful removal would most probably also allow retention of all other possible micropollutants. High performance composite RO membranes will be prepared by interfacial polymerzation for see or brackish water desalination. The parameters to be optimized will refer to membrane composition (polymer concentration, solvent) but also for first time, on the level of the membrane synthesis process and post treatment (temperature, annealing time), which via classical research have proven to have a great impact on membrane performance.

Genetic Algorithms (GA), Artificial Neural Networks (ANN) and Active Learning using Gaussian Processes (GP) are different multi- parameter optimization techniques. GA, the combination (hybrid) of GA with ANN, and GP will be compared to evaluate which approach leads faster to the best optimum. GAs are stochastic search techniques inspired by the principles of natural evolution. If a membrane is experimentally found to be more successful it will have more offspring and more variants (generated by mutation and crossover) of it will be tested in the following experiments. ANNs are data mining techniques used to model complex functions in multidimensional spaces and can be trained using earlier observations. A GA can be combined with an ANN in a hybrid process where the neural network models the fitness of the individuals of the GA. The model is used to avoid doing experiments defined as very unpromising by the ANNS in the next generation. This hybrid approach has already shown advantages over the use of only a GA[3] by reducing the population size and the number of generations. Active learning has recently been introduced into the field of function optimization using Gaussian Process regression as the underlying predictive model. GPs are a fully Bayesian probabilistic modelling framework. A key property of a GP model is that it provides both a prediction and an uncertainty interval, hence allowing the active learning strategy to explicitly trade off exploration of the search space against exploitation of the knowledge gained through previous experiments. This results in finding the optimal points in a smaller number of experiments.

[1] A.I. Schäfer, A.G. Fane, T.D. Waite, Nanofiltration principles and applications, Elsevier, 2003.

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[2] P. Vandezande, L.E.M. Gevers, J.S. Paul, I. F.J. Vankelecom, P. A. Jacobs. Journal of Membrane Science 250 (2005) 305-310. [3] J. M. Serra, A. Corma, S. Valero, E. Argente, V. Botti. QSAR and Combinatorial Science 26 (2007) 11-26.

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Drinking and Wastewater Applications IV – 5

Thursday July 17, 11:00 AM-11:30 AM, Honolulu/Kahuku

Study of an External MBR for Degradation of Endocrine Disrupter 17(alpha)-ethinylestradiol

L. Clouzot (Speaker), University of Aix-Marseille, France B. Marrot, University of Aix-Marseille, France - [email protected] P. Doumenq, University of Aix-Marseille, France N. Roche, University of Aix-Marseille, France

The xenobiotic 17±-ethinylestradiol (EE2), a common oral contraceptive component, is an endocrine disrupter with fish feminization induced at concentrations as low as 0.1 ng.L-1. EE2 occurrence in the aquatic environment (0.5-5 ng.L-1) is due to inefficient removal in municipal wastewater treatment plants (WWTPs). EE2 biodegradation is achieved by nitrifying micro- organisms (autotrophic biomass), characterized by slow growth. Therefore, EE2 removal requires activated sludge (AS) with a high sludge retention time (SRT). However, in WWTPs, there is often an incomplete separation of water and AS, resulting in low biomass concentrations and low SRTs. Membrane bioreactors (MBRs), with a complete physical retention of AS, are a promising solution to enhance EE2 degradation. During the past 10 years, an exponential increase in MBRs research and literature has been observed worldwide. Membrane fouling is a key issue that has slowed MBR technology commercialization; however, a significant increase in the breadth of application areas is anticipated. The aim of this study is to use MBR technology to improve EE2 elimination during municipal wastewater treatment. First, nitrifying AS acclimation was developed to obtain a specific biomass effective for EE2 degradation. Subsequently, purification of a synthetic wastewater containing EE2 will be tested in an external MBR with the acclimated AS. External MBR configuration has been selected because it results in a more effective biomass, and fouling is easier to control. Compared to immersed MBRs, floc size is smaller in external MBRs, providing a greater exposed surface area. To limit fouling during purification experiments, operational MBR conditions were optimized beforehand; hydrodynamics parameters and flux were adjusted. Acclimation of nitrifying AS from municipal WWTPs was developed in an 80 L immersed MBR with a SRT of 30 days. An immersed MBR provides a less harsh environment for AS acclimation because the bacteria are not recycled through a pump (as is the case for external MBRs). Autotrophic characteristics of the biomass required a culture media composed of NaHCO3 (inorganic carbon source), (NH4)2SO4 (energy and nitrogen source) and mineral salt supplements (MgSO4, KH2PO4, CaCl2). The pH was controlled at 7 by automatic titration with NaHCO3. Biodegradation experiments were performed after 96 days of acclimation, with EE2 concentrations of 1 mg.L-1, 500 µg.L-1 and 250 µg.L-1. Sample analysis is currently underway. Membrane fouling

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behaviour was investigated in a 10 L external MBR (microfiltration), at constant operating conditions. Initial permeability was fixed at 265 L.h-1.m-2.bar-1, with a relative standard deviation of 8%. A mixed liquor suspended solids (MLSS) concentration of 10 g.L-1 was chosen. When MLSS was increased from 8 g.L-1 to 16 g.L-1, at a transmembrane pressure (TMP) of 2.5 bar and a crossflow velocity of 3 m.s-1, there was a 20% decrease in permeate flux. Critical flux, defined as the minimum flux that creates an irreversible deposit on the membrane [1], is the key parameter used to predict fouling. However, MBRs are typically operated at fluxes above the critical flux of the system. At 4 m.s-1 crossflow velocity, critical flux appeared between 0.7 and 0.9 bar, with a permeate flux of 70-85 L.h-1.m-2. Critical flux also depends on the membrane state. At 5 m.s-1, a new membrane had an irreversible fouling between 0.7 and 0.9 bar whereas a previously fouled membrane had a critical flux below 0.7 bar. One method for reducing membrane fouling consists of increasing the crossflow velocity. At a fixed TMP of 2.5 bar, when crossflow velocities were increased from 2 to 5 m.s-1, the permeate flux increased from 142%. Backpulses can also be used to reduce membrane fouling. For one-day experiments, with 2 and 4 m.s-1 crossflow velocities and 1 bar TMP, 1 s backpulses per minute did not improve flux permeate. A four-day experiment at 5 m.s-1 and 1 bar gave the same result. Therefore, backpulses can influence filtration but not during short term experiments. Previous research [2] has indicated extracellular polymeric substances (EPS) as the most significant factor affecting fouling in MBRs. EPS effects on fouling mechanisms occurring in the external MBR are currently being investigated. First, experiments without the membrane will show the effect of the pump shear stress on the EPS concentration. The same type of experiments, performed with the membrane, will show the effect of the membrane on the EPS concentration.

[1] Espinasse B, Bacchin P and Aimar P. On an experimental method to measure critical flux in ultrafiltration. Desalination; 2002, 146:91-96.

[2] Le-Clech P, Chen V and Fane TAG. Fouling in membrane bioreactors used in wastewater treatment. Journal of Membrane Science; 2006, 284:17-53.

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Drinking and Wastewater Applications IV – 6

Thursday July 17 ,11:30 AM-12:00 PM, Honolulu/Kahuku

Pressurized and De-pressurized Membrane Photoreactors for Removal of Pharmaceuticals from Waters

R. Molinari (Speaker), University of Calabria, Rende, Italy - [email protected] A. Caruso, University of Calabria, Rende, Italy P. Argurio, University of Calabria, Rende, Italy T. Poerio, University of Calabria, Rende, Italy

Pharmaceutically active compounds (PhACs) are an important group of toxic organic contaminants that are not completely removed during conventional wastewater treatments and, therefore, can be found with concentration levels up to the µg L-1 in sewage, surface and groundwater [1, 2]. Because of drawbacks of conventional purification methods, hybrid systems based on coupling membranes and photocatalysis could represent an useful solution to these problems [3, 4]. The photocatalytic process allows the complete degradation (mineralization) of the organic molecules in harmless products and, at the same time, using a suitable membrane, it is possible to retain the pollutant and its degradation products in the reaction environment, the recovery and reuse of the photocatalyst and the separation of clarified solution. Besides, an interesting perspective is the possibility to use photocatalysis exploiting the solar light as energy source [5], with significant energy saving. In this work the performance of two configurations of catalytic membrane photoreactors (pressurized and de-pressurized) in batch and continuous systems for the degradation of two pharmaceuticals (Gemfibrozil and Tamoxifen), using TiO2 as suspended catalyst, have been studied. With the aim to understand the influence of some parameters on the efficiency of membrane photoreactors, the effects of pH of aqueous TiO2 suspensions, recirculation flow rate and membrane clean-up were previously studied. In the experimental studies on membrane photoreactor two different operative procedures were used: in the first one (closed membrane system) the permeate was continuously recycled, with the aim to determine the ability of the membrane to retain the drug and the oxidation products in the oxidant environment, while in the second one, in order to simulate the continuous photodegradation process that could be applied at industrial level, the removed permeate was replaced by an equal volume of initial feed drug solution. The achieved data showed that the photodegradation of the two selected drugs resulted quick and complete with a drug abatement of 99 % in the first 20 minutes and a mineralization higher than 90 % in about 120 minutes in the batch membrane system. Nevertheless a small or no- rejection to degradation products of both the drugs was evidenced. Tests in the pressurized continuous system, performed with Gemfibrozil solutions, underlined a good system operating stability, reaching a steady state in ca. 120 minutes with a complete abatement of

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the drug and values of mineralization (60 %) and permeate flux (38.6 L h-1 m-2) that remained constant until the end of a run. The TOC rejection of about 62 % at steady state showed the need to identify a membrane with higher rejection to the intermediate products, to maintain almost all of them in the reaction environment for the necessary time to reach their complete degradation. One of the major problems observed in the NF membrane photoreactor with the suspended catalyst is the membrane flux decline due to catalyst deposition and membrane fouling. To solve this problem our research has been addressed towards the use of a different configuration of membrane photoreactor, the de- pressurized (submerged) membrane system, in which the submerged membrane module was located separately from the photoreactor and the oxygen was bubbled on the membrane surface. The results obtained in this system confirmed that the presence of the suspended catalyst allows a complete degradation of Gemfibrozil in about 15 - 20 minutes and a partial mineralization of the organic intermediates with a TOC value at steady- state in the retentate of about 4.2 ± 0.7 mg L-1, though the no TOC rejection underlined the necessity to identify a membrane selective to intermediate products. The submerged membrane photoreactor, however, resulted more advantageous in terms of permeate flux, with values almost two times (65.1 L h-1 m-2) greater than those measured with the pressurized membranes. Actually, other types of membranes, more selective to substrates and intermediates, are under consideration.

[1] M.J. Gòmez, M.J. Martìnez Bueno, S. Lacorte, A.R. Fernàndez-Alba, A. Aguera, Chemosphere, 66 (2007) 993.

[2] L. Comoretto and S. Chiron, Sci. Total Environ., 349 (2005) 201.

[3] R. Molinari, F. Pirillo, V. Loddo, L. Palmisano, Catal. Today, 118 (2006) 205.

[4] R. Molinari, F. Pirillo, M. Falco, V. Loddo, L. Palmisano, Chem. Eng. Process., 43 (2004) 1103.

[5] V. Augugliaro, E. Garcia-Lopez, V. Loddo, S. Malato-Rodriguez, I. Maldonado, G. Marcì, R. Molinari, L. Palmisano, Sol. Energy, 79 (2005) 402.

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Drinking and Wastewater Applications IV – 7

Thursday July 17, 12:00 PM-12:30 PM, Honolulu/Kahuku

Mechanisms governing the effects of membrane fouling on the nanofiltration of micropollutants

L. Nghiem (Speaker), University of Wollongong, Wollongong, Australia - [email protected] C. Espendiller, University of Wollongong, Wollongong, Australia G. Braun, University of Applied Science Cologne, Cologne, Germany

The influence of membrane fouling on the retention of five micropollutants namely sulfamethoxazole, ibuprofen, carbamazepine, bisphenol A, and triclosan by nanofiltration membranes was investigated in this study. Humic acid, alginate, bovine serum albumin, and silica colloids were selected as model foulants to simulate various organic fractions and colloidal matter that are found in secondary treated effluent and surface water. Membrane fouling was achieved with foulant cocktails containing individual model organic foulants in a background electrolyte solution. The effects of membrane fouling on the separation process was delineated by comparing retention values of clean and fouled membranes and relate them to the membrane properties (under both clean and fouled conditions) as well as physicochemical characteristics of the micropollutants. Results reported here indicate a strong correlation between membrane fouling, foulant characteristics, and membrane properties. The effects of fouling on retention were found to be membrane pore size dependent. It was probable that the influence of membrane fouling on micropollutant retention could be governed by four distinctive mechanisms: modification of the membrane charge surface, pore constriction, cake enhanced concentration polarisation, and modification of the membrane hydrophobicity. The presence of the fouling layer could affect the retention behavior of charged solutes by altering the membrane surface charge density. While the effect of surface charge modification was clear for inorganic salts, it was less obvious for the negatively charged pharmaceutical species (sulfamethoxazole and ibuprofen) examined in this investigation, possibly due to the interference of the pore constriction mechanism. Behavior of the very loose TFC-SR2 membrane was found dominated by pore constriction and this membrane consistently showed an increase in retention under fouled conditions. In contrast, evidence of the cake enhanced concentration polarisation effect was observed with the smaller pore size NF-270 and NF-90 membranes, particularly under colloidal fouling conditions. In addition, the fouling layer could also interfere with the solute membrane interaction, and therefore, exerted considerable influence on the separation process of the two hydrophobic micropollutants bisphenol A and triclosan used in this study.

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Inorganic Membranes II – 1 – Keynote

Thursday July 17, 8:15 AM-9:00 AM, O’ahu/Waialua

High Temperature Gas Permeation Characteristics of MFI and DDR type Zeolite Membranes

J. Lin (Speaker), Arizona State University, Tempe, Arizona, USA - [email protected] M. Kanezashi, Arizona State University, Tempe, Arizona, USA J. O'Brien-Abraham, Arizona State University, Tempe, Arizona, USA X. Zhu, Arizona State University, Tempe, Arizona, USA

This presentation compares synthesis and gas permeation/separation properties of two thermally stable zeolite membranes: intermediate pore MFI type and small pore DDR type zeolite membranes. These membranes have minimized defects and pinholes and exhibit unique gas separation and permeation properties for separation and membrane reactor applications. Experimental data for permeation of small gases such as hydrogen, helium, carbon dioxide and carbon monoxide through these two zeolite membranes in the temperature range of 25-500°C will be presented and analyzed by the translational gas permeation model. The permeation and separation properties of these small gases at high temperatures for these microporous membranes feature a combined Knudsen and activated diffusion mechanisms, depending on the relative size of the diffusing gas to the membrane pores and quality of the membranes. The experimental data show that at high temperatures the molecules of these gases in the zeolite pores retain their gas characteristics. For MFI type zeolite membranes, the permeance decreases with increasing temperature and is determined by the molecular weight, not the kinetic diameter of the molecules. Diffusion of small molecules in the small pore DDR type zeolite membranes exhibits activated process, with permeance decrease with increasing size of the molecules.

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Inorganic Membranes II – 2

Thursday July 17, 9:30 AM-10:00 AM, O’ahu/Waialua

Adding Ion-Selective Functionality to Desalination Membranes with Unique Charge and Structural Properties of MFI Silicalite and ZSM-5 Zeolites

M. Duke (Speaker), Victoria University, Melbourne, Australia - [email protected] J. Lin, Arizona State University, Tempe, Arizona, USA J. Diniz da Costa, The University of Queensland, St. Lucia, Australia

Inorganic membranes such as zeolites have unique structural and surface properties which can be tailored to achieve ion-selective desalination. In this work we show how variation in the Si/Al ratio of MFI membranes influences not only membrane flux, but also the ability for the membrane to selectively pass specific ions in seawater. In membrane distillation, the pure silicalite membrane exhibited NaCl rejection from 3.8 wt% seawater of 97%, but alumina containing ZSM- 5 membranes showed outstanding rejections >99.5%. With most membrane formulations, permeate flux decreased upon switching form fresh water feeds to seawater, however the Si/Al = 100 membrane displayed a unique potential to increase flux by 30% when seawater was introduced. Also, for the same membrane, rejection was discovered to switch to negative values (-80%) after increasing the feed pressure to 700kPa using 0.5 wt% seawater feeds. Ions in seawater clearly influence the zeolite structure in ways which allow either total rejection or salt enrichment through the membrane, serving niche ion- selective applications, or potentially reducing the energy required for desalination.

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Inorganic Membranes II – 3

Thursday July 17, 10:00 AM-10:30 AM, O’ahu/Waialua

Carbonate-Ceramic Dual-Phase Membrane for High Temperature Carbon Dioxide Separation

M. Anderson (Speaker), Arizona State University, Tempe, Arizona, USA J. Lin, Arizona State University, Tempe, Arizona, USA - [email protected]

Carbon dioxide is produced as a byproduct in many industrial processes, such as the generation of electricity via coal combustion. Flue gas from conventional coal-burning power plants contains roughly 13% carbon dioxide, 73% nitrogen, 10% water, 3% oxygen and less than 1% various pollutants. It is of increasing importance to find ways to effectively separate carbon dioxide because it is a known greenhouse gas. In this work we report the synthesis of a novel carbonate-ceramic dual-phase membrane for improved high temperature carbon dioxide separation. The dual-phase membrane is composed of a ceramic (solid) phase, which acts as a support for a molten carbonate (liquid) phase. La(0.6)Sr(0.4)Co(0.8)Fe(0.2)O(3-delta) (LSCF) was chosen as the support material to take advantage of its mixed conductivity and improved oxidation resistance in comparison to the previously used metallic dual-phase membrane.

LSCF supports were prepared by pressing and sintering powder synthesized using the citrate method at 900 C. The pore radius of the sintered LSCF supports was determined to be approximately 330 nm via both steady state helium permeance and mercury porosimetry measurements. Dual-phase membranes were successfully prepared by direct infiltration of molten carbonate at 520 degrees C. Helium permeances of the LSCF support before and after infiltration were on the order of 10-6 and 10-10 mol/s.m2.Pa respectively, indicating that the membrane was completely infiltrated. High temperature carbon dioxide permeation experiments were performed from 650-900 C by feeding carbon dioxide and argon on the upstream side of the membrane, and using helium as a sweep gas on the downstream side of the membrane. It was observed that LSCF’s relatively high oxygen ion conductivity made it possible for the support to provide oxygen ions and facilitate formation of CO3

= in accordance with the following reaction: CO2 + O= CO3

=. Upon reaching the downstream side of the membrane, the reverse reaction occurs, leading to separation of pure carbon dioxide. The LSCF dual-phase membrane exhibited a high carbon dioxide permeance of 3.6x10-8 mol/s.m2.Pa at 900 C. Additionally, the amount of argon present in the permeate was found to be lower than the detection limit (~10-10 mol/s.m2.Pa) of the gas chromatograph, indicating an ideal separation factor of carbon dioxide over argon of at least 360. The activation energy for this membrane was found to be 75 kJ/mol, which is comparable to the values for the activation energy of oxygen vacancy diffusion in this particular material. This

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confirms that the carbon dioxide permeance through the dual-phase membrane is largely controlled by oxygen ion conductivity of the ceramic phase. A theoretical model was developed to predict the high temperature permeation characteristics for the material studied. It was found that the experimental results and theoretical predictions were in agreement, furthering proving the feasibility of the carbonate-ceramic dual-phase membrane.

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Inorganic Membranes II – 4

Thursday July 17, 10:30 AM-11:00 AM, O’ahu/Waialua

High Quality Tubular Silica Membranes for Gas Separation

M. Luiten (Speaker), University of Twente, The Netherlands - [email protected] C. Huiskes, University of Twente, The Netherlands H. Kruidhof, University of Twente, The Netherlands A. Nijmeijer, University of Twente, The Netherlands

Highly selective silica membranes have been made on repaired extruded commercial ±-Al2O3 tubular supports with lengths of 10 and 55 cm. To decrease the surface roughness of commercial extruded ±- Al2O3 tubular supports Pervatech (Enter, Netherlands) developed a repairing technology. Silica membranes coated on the inside of these repaired commercial ±- alumina tubes (10 resp. 55 cm) have been prepared and analysed by using SEM, permporometry, XPS and single gas permeance measurements. These permeance measurements were carried out at temperatures between 100 and 450ºC. The hydrogen permeance (at 450ºC) was around 2x10-6 mol m-2 s-1 Pa-1 and the permselectivity for hydrogen over light gases was very high; F(H2/CH4) > 1200, F(H2/CO2) >100 and the F(H2/N2) = 250. A long term (>2600 h) permeation test shows that the permeance of hydrogen (at 200ºC and ΔP=3.8bar) was in the range of 6-8x10-7 mol m-2 s-1 Pa-1. The excellent gas separation performance of the silica membrane on a tube with a length of 55 cm indicates a large potential for the future of these membranes as it opens the way for a large number of industrial applications.

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Inorganic Membranes II – 5

Thursday July 17, 11:00 AM-11:30 AM, O’ahu/Waialua

Recent Developments on the Preparation and Modeling of Nanoporous Silicon Carbide Membranes for Gas Separation Applications

R. Mourhatch (Speaker), University of Southern California, Los Angeles, Califorinia, USA - [email protected] B. Elyassi, University of Southern California, Los Angeles, Califorinia, USA F. Chen, University of Southern California, Los Angeles, Califorinia, USA M. Sahimi, University of Southern California, Los Angeles, Califorinia, USA T. Tsotsis, University of Southern California, Los Angeles, Califorinia, USA

Silicon carbide (SiC) is a material with very attractive chemical and physical properties, which have made it a great candidate for membrane applications, especially those related to gas separation and hydrogen production. The focus of the present paper is on using two different approaches to prepare asymmetric nanoporous silicon carbide membranes which are applicable in reactive separations involving the water-gas shift and methane steam reforming reactions, where the membrane has to function in the presence of high-temperature steam. The first approach for the preparation of SiC microporous membranes, involves the pyrolysis of thin allyl-hydridopolycarbosilane (AHPCS) films coated, using a combination of slip-casting and dip-coating techniques, on tubular SiC macroporous supports. Combining slip-casting with dip-coating significantly improved the reproducibility in preparing high quality membranes. The membranes were studied for their transport characteristics, and steam stability. In addition, a novel method, based on the use of sacrificial interlayers, was also developed for the preparation of nanoporous SiC membranes, which involves periodic and alternate coatings of polystyrene sacrificial interlayers and SiC AHPCS layers on the top of slip-casted tubular SiC supports. Membranes prepared by this technique exhibit single gas ideal separation factors of He and hydrogen over Ar in the range of (176-420) and (100-200), respectively, with permeances that are typically two to three times higher than those of SiC membranes prepared previously by the more conventional techniques.

Preparation of asymmetric nanoporous SiC membranes is also carried out using chemical-vapor infiltration/chemical-vapor deposition (CVI/CVD) techniques. We have used macroporous SiC disks and tubes as supports, and tri-isopropylsilane as the precursor. We have also developed two dynamic models to describe the preparation and the transport characteristics of the membranes by the CVD/CVI technique. First, a coarse-grained pore network model was developed for the membranes, that provides accurate predictions for the ideal selectivities, as well as the transport of binary gas mixtures. A continuum model of the CVD/CVI membrane preparation process has also been developed, which is validated by the results of a comprehensive experimental study. The results of the model

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indicate that the CVI/CVD process of the TPS on the SiC support continues only so long as the pore sizes are larger than the molecular radius RTPS of the TPS. Once the pores shrink to a size smaller than (or equal to) RTPS, the permeance of argon no longer changes, even if one continues the deposition process. Moreover, the model shows that, significant porosity changes occur mostly in the region very close to the top surface. We have optimized the model in order to achieve the best operating conditions for preparing high quality membranes.

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Inorganic Membranes II – 6

Thursday July 17, 11:30 AM-12:00 PM, O’ahu/Waialua

Preparation and Gas Separation Performance of Carbon Hollow Fiber Membrane Module

M. Yoshimune (Speaker), AIST, Tsukuba, Japan - [email protected] K. Haraya, AIST, Tsukuba, Japan

We have studied carbon molecular sieve membranes derived from poly(phenylene oxide) (PPO) as a new type of carbon precursor. Carbon hollow fiber membranes are promising for the industrial use of membrane modules, however, one of the main problems of carbon hollow fiber is brittleness. In this study, a flexible carbon hollow fiber membrane derived from PPO derivative is investigated and a membrane module containing hundreds of carbon hollow fibers is successfully prepared. This carbon hollow fiber membrane module showed not only better mechanical stability but excellent performance for the gas separation such as CO2/CH4.

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Inorganic Membranes II – 7

Thursday July 17, 12:00 PM-12:30 PM, O’ahu/Waialua

Viability of ITM Technology for Oxygen Production and Oxidation Processes: Material, System and Process Aspects

M. den Exter (Speaker), Energy Research Centre of the Netherlands, Petten, The Netherlands - [email protected] W. Haije, Energy Research Centre of the Netherlands, Petten, The Netherlands J. Vente, Energy Research Centre of the Netherlands, Petten, The Netherlands

The threat of global warming due to increasing CO2 concentrations has been recognized as one of the main environmental challenges of this century. To limit atmospheric CO2 concentrations to acceptable levels, major changes in energy consumption are required in the coming decades. Still, fossil fuels are widely expected to remain the world’s major source of energy for well into the 21st century. While supply of oil and gas is under threat due to political instability and uncertainties on reserves, the use of coal is increasing, with concomitant higher CO2 emissions. To meet the targets set for atmospheric CO2 concentrations, the development of break through technologies is essential. Otherwise, it will proof to be impossible to reach the dramatic decrease of the CO2 emission to the atmosphere during the conversion of fossil fuels to other forms of energy, e.g. electricity or hydrogen. Three main routes for mitigation of CO2 emissions in electricity plants can be defined:

1. Post-combustion processes: CO2 is captured from the flue gases. 2. Pre-combustion processes: The fuel (natural gas or coal) is converted into hydrogen and CO2. The CO2 is separated and hydrogen is combusted in a gas turbine. 3. Oxyfuel processes: Combustion is carried out using pure oxygen, resulting in a flue gas that mainly contains H2O and CO2.

These routes are connected with carbon capture with subsequent sequestration. An additional approach is to avoid the production of CO2 emissions altogether through increased industrial energy efficiency and thus lower energy consumption. Oxygen production is related to the last two points.

This contribution is devoted to the state of the art of ionic transport membrane (ITM) technology as alternative for energy-demanding distillations in large-scale oxygen production. The most important aspects in the development of high temperature ceramic air separation membranes, based on perovskite as oxygen conducting material, will be treated starting from membrane development to module designs and process schemes. Development of (tubular) membranes will be explained in terms of preparation methods and choice of perovskite-types. The latter is based on physical and chemical properties such as oxygen

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permeability, stability issues comprising kinetic phase demixing, creep, unwanted phase transitions and manufacturing issues that come to for. Module concepts, based on single-hole tubes, monoliths, hollow-fibers and plate-tube designs will be shown and techno-economically evaluated, directing the choice of the most desirable membrane configuration while sealing design options will be revealed, based on chemical/physical issues and economical viability.

Additionally, fields of application of ITM technology will be discussed in terms of oxygen consumption in chemical processes.

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Fuel Cells II – 1 – Keynote

Thursday July 17, 8:15 AM-9:00 AM, Wai’anae

Fuel Cell Membranes from Nanofiber Composites

R. Wycisk (Speaker), Case Western Reserve University, Cleveland, Ohio, USA - [email protected] J. Choi, Case Western Reserve University, Cleveland, Ohio, USA K. Lee, Case Western Reserve University, Cleveland, Ohio, USA P. Pintauro, Case Western Reserve University, Cleveland, Ohio, USA P. Mather, Syracuse University, Syracuse, New York, USA

New generation of proton conducting membranes meeting the needs of the emerging fuel cell industry will have to appear soon if fuel cells are to play an important role in the transformation towards greener energy production. Those membranes will combine the latest developments in both materials chemistry and nanomorphology control.

The most obvious trend in sulfonic acid type membrane polymers is to increase the sulfonation degree so as to maximize proton conductivity and water retention capability, which are especially important for applications in hydrogen fuel cells. Unfortunately, this approach leads to problems with membrane dimensional/mechanical stability. Recent studies on the advantageous nanomorphologies of multiblock sulfonic copolymers open up an interesting avenue for improvements. Still this approach has limits imposed by the monomer/oligomer reactivity, block stoichiometry and casting solvent availability.

An entirely new approach for fabricating fuel cell membranes has been developed by the present authors. It can be universally applied to a wide range of proton conducting materials. Briefly, a three-dimensional, interconnected network of proton-conducting polymer nanofibers fabricated via electrospinning is embedded in an inert/impermeable polymer matrix. The nanofiber network, occupying about 40-70% of the dry membrane volume, is composed of a high ion-exchange capacity sulfonic acid polymer to ensure high water affinity and a high concentration of protogenic sites. The inert (hydrophobic) polymer matrix controls water swelling of the nanofibers and provides overall mechanical strength to the membrane. Unlike other fuel cell membranes, the role of the mechanical support is decoupled from that of the proton conductor. This composite structure is also free from the limitations imposed by the percolation effects typical of classic phase-separated systems.

The talk will be on the experimental details of nanofiber composite membranes fabrication. Water swelling, proton conductivity, and thermal/mechanical properties of the resulting membranes will be discussed.

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Fuel Cells II – 2

Thursday July 17, 9:30 AM-10:00 AM, Wai’anae

Hybrid Nanocomposite Membranes for PEMFC Applications

B. Lafitte (Speaker), Commissariat à l’Energie Atomique, Monts, France - [email protected] F. Niepceron, Commissariat à l’Energie Atomique, Monts, France J. Bigarre, Commissariat à l’Energie Atomique, Monts, France H. Galiano, Commissariat à l’Energie Atomique, Monts, France

Fuel cells[1,2] are important enabling technologies for the reduction of green-house gases emissions, offering cleaner, more-efficient alternatives to combustion of gasoline and other fossil fuels. Current Polymer Electrolyte Membrane Fuel Cell (PEMFC) systems predominantly use perfluorosulfonic acid based membranes, such as Nafion®. However, Nafion® membranes tend to significantly dehydrate at high temperatures or at low relative humidity leading to low proton conductivity and poor PEMFC performance under these conditions. Thus, new proton exchange membrane (PEM) materials have been developed in order to increase the performance over a large temperature window and at low humidification.

These new materials[3-5] are based on a hybrid organic-inorganic formulation in which the inorganic phase contributes to the enhancement of the water retention properties around 100°C. In particular, the development of a new family of PEMs where the proton conductive characteristics rely exclusively on the inorganic phase gives promising results.[6] In the present contribution, a report of the incorporation of original acid-functionalized inorganic nanoparticles in inert membranes (low-cost polymer) is given. Membranes with different amounts of inorganic particles have been prepared by evaporation and recasting techniques. These membranes were tested for their proton conductivities and their morphologies have been investigated. Finally, the performance of membrane-electrode assemblies (MEAs), using selected hybrid membranes, was evaluated by single cell fuel cell tests. Remarkably, such hybrid membrane systems exhibited up to 1.2 W/cm2, at 80 °C using non-hydrated gas feeds.

ACKNOWLEDGEMENTS This work was carried within the framework of a Pan-H program financed by the Agence Nationale pour le Recherche and co-supported by the Commissariat à l’Energie Atomique and the Region Centre.

REFERENCES

1. Song, C. Catalysis Today 2002, 77, 17.

2. Costamagna, P.;Srinivasan, S. Journal of Power Sources 2001, 102, 242.

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3. Shao, Z.-G.; Loghee, P.; Hsing, I.-M. Journal of Membrane Science. 2004, 229, 43.

4. Kwak, S.-H. Solid State Ionics 2003, 160, 309.

5. Chang, H. Y.; Lin, C. W. Journal of Membrane Science. 2003, 218, 295.

6. Bébin, P.; Caravanier, M.; Galiano, H. Journal of Membrane Science. 2006, 278, 35.

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Fuel Cells II – 3

Thursday July 17, 10:00 AM-10:30 AM, Wai’anae

Hybrid Self-Organized Membranes: New Strategies for Promising Fuel Cell Energy Applications

M. Michau, Institut Europeen des Membranes, Montpellier, France M. Barboiu (Speaker), Institut Europeen des Membranes, Montpellier, France - [email protected]

Artificial membrane materials are the subject of various investigations,offering great potentialities as well on the level of their chemical composition or organization as to that of the concerned applications. Of special interest is the structure-directed function of hybrid membrane materials and control of their build-up from suitable units by self- organisation.

The main interest focus on functional hybrid membranes in which the recognition-driven transport properties could be ensured by a well- defined incorporation of receptors of specific molecular recognition and self-organization functions, incorporated in a hybrid dense materials.

Actual and potential applications of such self- organized systems can emerge for new membrane materials presenting combined features of structural adaptation in specific nanodomains randomly ordered in the hybrid matrix. These oriented nanodomains are resulted from the controlled self-assembly of simple molecular components that encodes the required information for ionic assisted-diffusion within hydrophilic pathways. Our results simply that the control of molecular interactions can define the self- organized supramolecular architectures presenting a strong communication between the organic and the siloxane layers. Although these pathways do not merge to cross the micrometric films, they are well defined along nanometric distances. It results that these systems may transport protons through structure diffusion under low-humidity conditions. In addition some potential research directions for the development of new efficient fuel cell PEMFC materials presenting enhanced conduction properties.

[1] A. Cazacu, C. Tong, A. van der Lee, T.M. Fyles, M. Barboiu, J. Am. Chem. Soc. 2006, 128 (29), 9541-9548.

[2] C. Arnal-Herault, A. Pasc-Banu, M. Michau, M. Barboiu, Angew. Chem. Int. Ed. 2007, 46, 8409- 8413.

[3] C. Arnal-Hérault, M. Barboiu, A. Pasc, M. Michau, P. Perriat, A. van der Lee, Chem. Eur. J. 2007, 13, 6792

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[4] M. Michau, M. Barboiu, R. Caraballo, C. Arnal- Hérault, A. van der Lee, Chem. Eur. J. 2008, 14, 1776-1783.

[5] C. Arnal-Herault, A. Pasc-Banu, M. Barboiu A. van der Lee, Angew. Chem. Int. Ed. 2007, 46, 4268- 4272.

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Fuel Cells II – 4

Thursday July 17, 10:30 AM-11:00 AM, Wai’anae

Ion-Exchange Membranes from Side-Chain Sulfonated Poly(arylene ether)s

J. Meier-Haack (Speaker), Leibniz Institute of Polymer Research Dresden, Dresden, Germany - [email protected] K. Schlenstedt, Leibniz Institute of Polymer Research Dresden, Dresden, Germany W. Butwilowski, Leibniz Institute of Polymer Research Dresden, Dresden, Germany C. Vogel, Leibniz Institute of Polymer Research Dresden, Dresden, Germany

Polymer electrolyte membranes and in particular cation exchange membranes are used in a broad field of applications such as low fouling membranes in water and wastewater treatment, solid polymer electrolytes in electrochemical processes (e.g. low temperature fuel cells) or as ion-selective membranes in sensors.

Despite of some drawbacks, today poly(perfluoroalkylsulfonic acid)s such as Nafion® and similar materials are still the standard membrane materials for polymer electrolyte fuel cells (PEMFC). The disadvantages of these materials and the demand for new energy conversion/production systems have initiated world-wide research activities on the development of alternative membrane materials for PEMFC. Among the various materials suggested, sulfonated poly(arylene ether)s are seen as the most promising ones due to their outstanding chemical and thermal stabilities, high glass transition temperature (Tg) as well as their good solubility in dipolar aprotic solvents such as N-methyl-2-pyrrolidone (NMP), dimethylsulfoxide (DMSO) or N,N- dimethylacetamide (DMAc) and film forming properties. However these materials have two main disadvantages over Nafion-like materials, namely: (1) the hydrolytic instability of aromatic sulfonic acids [1] and (2) the lower acidity of the sulfonic acid groups, leading to lower conductivities at comparable ion-exchange capacities.

Vogel et al. reported on a surprisingly high hydrolytic stability of polystyrene sulfonic acid [1]. First indications of hydrolysis were found only after treatment in water at 200°C for 24h. On the other hand poly(styrene sulfonic acid) is not suitable for applications in fuel cells due to its chemical instability arising from the tertiary carbon in the polymer backbone. These results led us to the idea to prepare chemically stable poly(arylene ethers) with a pending phenyl ring, which can be sulfonated selectively, in order to mimic poly(styrene sulfonic acid). Having the sulfonic acid group in the side chain has further advantages as has been described in the literature by Lafitte et al. [2 - 4] or Guiver et al. [5]. Recently, we reported on poly(arylene ether)s prepared from bis-(4- fluorophenyl)-sulfone bis-(4-hydroxyphenyl)- sulfone and phenylhydroquinone [6, 7], which can be selectively sulfonated at the external benzene ring. Secondly, to

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support a phase separation between sulfonated and non-sulfonated domains, block copolymers have been prepared. A block copolymer with short segments showed similar or better transport properties as the random copolymer of same composition. It is expected that blockcopolymers with longer blocksegments will show better performance than their random counterparts. The properties will be further discussed in terms of proton conductivities and PEMFC-performance.

[1] C. Vogel, J. Meier-Haack, A. Taeger, D. Lehmann, Fuel Cells 4, 320 (2004).

[2] B. Lafitte, L. E. Karlsson, P. Jannasch, Macromol. Rapid Commun. 23, 896 (2002).

[3] L. E. Karlsson, P. Jannasch J. Membr. Sci. 230, 61 (2004).

[4] B. Lafitte, P. Jannasch J. Polym. Sc.: Part A: Polym. Chem. 43, 273 (2005).

[5] B. Liu, G. P. Robertson, D.-S. Kim, M. D. Guiver, W. Hu, J. Zhenhua Macromolecules 40, 1934 (2007).

[6] J. Meier-Haack, C. Vogel, W. Butwilowski, K. Schlenstedt, D. Lehmann Pure and Applied Chemistry 79, 2083 (2007).

[7] J. Meier-Haack, C. Vogel, H. Komber, W. Butwilowski, K. Schlenstedt, D. Lehmann Macromol. Symp. 254, 322 (2007).

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Fuel Cells II – 5

Thursday July 17, 11:00 AM-11:30 AM, Wai’anae

Ionomer Blend Membranes for Low T and Intermediate T Fuel Cells

J. Kerres (Speaker), University of Stuttgart, Stuttgart, Germany - [email protected] F. Schoenberger, University of Stuttgart, Stuttgart, Germany M. Schaefer, University of Stuttgart, Stuttgart, Germany A. Chromik, University of Stuttgart, Stuttgart, Germany K. Krajinovic, University of Stuttgart, Stuttgart, Germany V. Gogel, Zentrum für Sonnenenergie- und Wasserstoff-Forschung, Ulm, Germany L. Jörissen, Zentrum für Sonnenenergie- und Wasserstoff-Forschung, Ulm, Germany Q. Li, Technical University of Denmark, Lyngby, Denmark J. Jensen, Technical University of Denmark, Lyngby, Denmark N. Bjerrum, Technical University of Denmark, Lyngby, Denmark

This contribution comprises an overview about the work done by our research group in the development of ionomers/ionomer (blend) membranes for membrane fuel cells. The topics include the development of novel sulfonated arylene main chain nonfluorinated and partially fluorinated homo polymers, block and statistical copolymers by nucleophilic displacement polycondensation procedures; the preparation of covalently or ionically cross-linked membranes prepared by mixing these polymers with PBI Celazol or other basic polymers; the application of these membranes to PEFC and DMFC, particularly up to a temperature of 60°C under atmospheric pressure (air-breathing) for the application in micro fuel cells; development of novel base-excess PBI/sulfonated polymer/H3PO4 blend membranes, and test of these membranes in fuel cells at intermediate fuel cell operation temperatures (170-200°C). From the sulfonated ionomers, acid-excess ionically cross-linked membranes have been prepared by mixing the sulfonated ionomer with the basic polymer PBI.Covalently cross-linked blend membranes have been prepared by blending sulfonated arylene polymers with PSU-sulfinate under cross-linking of the sulfinate groups with different cross-linkers via sulfinate S-alkylation. These membranes have been tested in a DMFC to investigate their suitability for the DMFC up to a temperature of 60°C under atmospheric pressure which is interesting for the use of DMFC as power supply for mobile electronic applications, under comparison with Nafion. The i/U polarization curves of the membranes along with their MeOH permeability, determined via monitoring the CO2 flux in the cathode effluent gas using an optical IR CO2 sensor, showed a better performance than Nafion which is mainly due to the lower meOH permeability of the arylene ionomer membranes, compared to Nafion. Membrane-electrode assemblies (MEAs) using the new ionomers have been built up using different methods: 1) by coating the membranes with anode and cathode inks; 2) by building up the MEA from the cathode; 3) by building up the MEA from the anode. Among all applied methods,

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1) yielded the MEAs with the best DMFC performance. One of the MEAs was tested for 4 weeks in a DMFC and showed continuously increasing performance within this period of time. PBI/sulfonated polymer/H3PO4 blend membranes for the application in intermediate T fuel cells have been developed as well. These membranes showed good performance in fuel cells in the temperature range 170-200°C, their chemical stability being even better than that of pure PBI membranes, which was ascertained by H2O2 and Fentons degradation test: during H2O2 treatment, the base-excess base-acid PBI blend membranes showed markedly less molecular weight degradation than pure PBI or sulfonated polymer, as determined by gel permeation chromatography (GPC).

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Fuel Cells II – 6

Thursday July 17, 11:30 AM-12:00 PM, Wai’anae

Hygrothermal Aging of Nafion

F. Thominette (Speaker), ENSAM, Paris, France - [email protected] F. Collette, ENSAM, Paris, France G. Gebel, CEA, Grenoble, France

1. Introduction

Nafion membranes are mostly used in PEMFC fuel cell as an electrolyte. Nafion molecular structure, in the acid form, consists of polytetrafluoroethylene hydrophobic backbone with perfluorinated pendant chains terminated by hydrophilic sulfonic groups. These hydrophilic end-groups permit water sorption, contributing to protons transport and, thus, to ionic conductivity. Water and temperature are viewed as systematically existing parameters in fuel cells in use. Their influence on the polymer is reported in this study. Our aim is to study the evolution of Nafion hydrophilicity properties with aging time and to link it with the modifications of its chemical structure.

2. Experimental

Commercial perfluorinated sulfonic acid membranes Nafion® 112 membranes were used as received for durability tests. Aging was done at 80° C, either at 0%RH or 80%RH. Samples were removed throughout aging and were characterized by Dynamical Vapour Sorption (DVS), infrared spectroscopy and nuclear magnetic resonance.

3. Results

For pristine sample, a sigmoidal isotherm is obtained by DVS. The concave part, for low activities, is relative to water molecules fixed preferentially on sulfonic acid groups. It corresponds to Langmuir population with strong interactions caused by hydrogen bonds. The quasi linear region of the sorption isotherm can be attributed to Henry mode sorption which corresponds physically to molecules of water sorbed by an ordinary dissolution mechanism, in the hydrophilic phase. At higher activities, the sorption isotherm displays a positive curvature that corresponds to the clusters formation. With aging, the isotherms are significantly modified. The most spectacular feature is the progressive disappearance of Langmuir contribution. This implies that the proportion of water sorbed on the Langmuir sites decreases with aging time, indicating that probably the number of sulfonic acid sites decreases too. It is also observed that the concentration of water at equilibrium decreases with aging time: At water activity of 0.9, for

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samples aged at 80%RH, water concentration decreases from 15% to 6.5% up to 80 days and remains constant beyond. With aging, Nafion absorbs less water: It becomes less hydrophilic.

Pristine and aged samples are analysed in parallel by infrared spectroscopy (transmission mode). The most spectacular phenomenon is the appearance of a new band at 1440 cm-1 which is clearly observed in all IR spectra of aged samples. The intensity of this absorbance band increases with aging and remains constant after exposure times very close to that observed from DVS measurements.

19F NMR spectra show that aged Nafion backbone is not chemically altered by aging but that the environment of chemical functions located on pendant chains is slightly modified.

To follow the influence of aging on the sulfonic groups of Nafion, 1H NMR MAS spectra of aged samples are observed in parallel of the 19F NMR spectra. In its original state, Nafion pristine membrane displays only one protonated site. 1H NMR spectra of Nafion aged in a climatic chamber display a second peak at 3.4ppm with aging. Heteronuclear correlation NMR experiments 1H- 13C did not point out any interaction of these protons with the carbonated structure of Nafion. This peak does not result from a chemical degradation of the polymer.

The same observations are done for samples aged at 80°C, 0%RH except that it evolves more slowly (stabilization over 200 days).

4. Discussion

One of the most interesting features of Nafion aging is the decrease of Nafion water uptake. After exposure at 80°C, Nafion becomes less hydrophilic as shown by DVS. Aged Nafion isotherms do not display Langmuir contribution anymore: water is no longer trapped by sulfonic acid end-groups as in pristine Nafion.

The apparition of an infrared absorption band at 1440 cm-1 strongly suggests anhydride formation and will be considered as a degradation tracer. The mechanism proposed here is a condensation of two sulfonic acids creating a cross-link S-O-S between two side groups which is accompanied by loss of one water molecule.

Modifications observed in 19F NMR reveals a change of the chemical environment of the pendant chains as expected by the anhydride formation. With aging, a new 1H NMR peak located at 3.4ppm appears after exposure at 0 or 80%RH. According to its chemical shift, this peak is attributed to non- acidic water molecules located around anhydrides. The observation of the non-acidic water peak at 3.4 ppm, on the 1H NMR spectra, can be considered as a tracer of the polymer aging.

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5. Conclusion

In this work, the evolution of Nafion chemical structure highlights sulfonic anhydrides formation, creating a cross-link between two side chains. This leads to the decrease of the polymer hydrophilicity with a proton conductivity drop off. These changes are observed for all aged samples.

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Fuel Cells II – 7

Thursday July 17, 12:00 PM-12:30 PM, Wai’anae

Automotive Hydrogen Fuel Cell Membrane Applications

A. Brenner (Speaker), General Motors, Honeoye Falls, New York, USA - [email protected] F. Coms, General Motors, Honeoye Falls, New York, USA C. Gittleman, General Motors, Honeoye Falls, New York, USA R. Jiang, General Motors, Honeoye Falls, New York, USA Y. Lai, General Motors, Honeoye Falls, New York, USA A. Nayar, General Motors, Honeoye Falls, New York, USA M. Schoeneweiss, General Motors, Honeoye Falls, New York, USA Y. Zhang, General Motors, Honeoye Falls, New York, USA

Automotive fuel cell systems have requirements that differ from other fuel cell applications. The challenge is dynamic operation over the wide range of operating conditions experienced by the vehicle during its 5500 hour target life. How the vehicle requirements translate to membrane targets and related testing is reviewed for two membrane focus areas within the automotive system: the PEM fuel cell stack and humidification subsystem. The in-situ and ex- situ measurements used to evaluate these membranes for use in commercial automotive fuel cells will be described in addition to corresponding targets and status.

Recovery of water from the cathode exhaust with a humidification membrane can extend the durability and enhance performance of the PEM. Water transport and gas separation are the key performance metrics of the humidification membranes. The primary functions of the PEM membrane are proton transport, gas separation and electrical insulation. The PEM can fail due to chemical degradation, mechanical degradation or a combination. The humidification membrane is subject to some similar factors contributing to mechanical degradation, such as high temperatures and drier conditions. Cycling of humidity and freeze and oxidative environments can also contribute to degradation. Durability, performance, and processability of each membrane are critical to meeting the cost, life, and performance targets of the fuel cell vehicle.

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Oral Presentation Abstracts

Afternoon Session

Thursday, July 17, 2008

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Hybrid and Novel Processes II – 1 – Keynote

Thursday July 17, 2:15 PM-3:00 PM, Kaua’i

Cyclic Hybrid Adsorbent-Membrane Reactor (HAMR) Studies for Hydrogen Production

A. Harale, University of Southern California, Los Angeles, California, USA H. Hwang, University of Southern California, Los Angeles, California, USA P. Liu, Media and Process Technology Inc., Pittsburg, Pennsylvania, USA M. Sahimi, University of Southern California, Los Angeles, California, USA T. Tsotsis (Speaker), University of Southern California, Los Angeles, California, USA - [email protected]

1. Introduction

As a result of stricter environmental regulations worldwide, hydrogen is progressively becoming an important clean energy source. For H2 to replace fossil fuels in mobile applications, it will require the creation of a production and delivery infrastructure equivalent to that currently existing for fossil fuels, which is an immense task. As an alternative, and as an interim step towards the new hydrogen economy, various groups are currently studying steam reforming of methane (SRM) for the on- board generation of hydrogen, or for on site production, in order to alleviate the need for compressed or liquid hydrogen gas storage(1-4). Conventional technologies are, however, neither convenient nor economical to apply for small-scale (on site or on-board) hydrogen generation. Reactive separation processes have, as a result, been attracting renewed interest for application in H2 production through SRM. One such technology is the hybrid adsorbent-membrane reactor (HAMR) system, which couples reaction and membrane separation steps with adsorption on the reactor and/or membrane permeate side. The HAMR concept was originally proposed by our group(5,6) for esterification reactions, and it was adapted recently for on-board or on-site hydrogen production applications. Our early studies involved the development of a mathematical model for the HAMR system (applied to hydrogen production through SRM(7)); recently experimental investigations with the water-gas shift reaction(8), using microporous membranes and CO2 hydrotalcite-type adsorbents, were carried out in order to validate the HAMR design models. Experimental data were compared with the model predictions, and found to be consistent. In this paper we focus on the practical process design aspects of the HAMR hydrogen production process. A continuous HAMR process scheme has been investigated, both experimentally and through modeling studies. 2. HAMR Cyclic Process The steps involved in the proposed cyclic HAMR process for the direct production of pure H2 are described below. It consists of four steps: 1.Adsorption-Reaction-Membrane Separation Step. The reactor is initially pre-saturated with H2 and steam at the desired reaction temperature and pressure. A mixture of steam and CH4 (or CO) at a prescribed ratio are fed to the reactor, and

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an essentially pure H2 product is collected at the permeate side. The reaction step is continued up to the time needed for breakthrough to occur. This time depends upon adsorbent and membrane characteristics, and membrane parameters such as the residence time, and transmembrane pressure.At the breakthrough point the feed is diverted into a second identical reactor. 2.Blow-down Step. The reactor is depressurized to a lower pressure of PL countercurrently to the feed flow direction. The effluent gas stream from this step contains all the components left in the reactor at the end of Step 1, and can either be recycled as a feed to another reactor or be used as fuel. 3. Purge Step.The reactor is countercurrently purged with a weakly adsorbing gas such as steam or H2 to desorb the CO2. The desorption step operates at PL. The desorbed gas consists of CO, CH4, CO2, H2, and H2O and is either separated for recycle or used as fuel. 4.Pressurization step. The reactor is countercurrently pressurized to the reaction pressure (for Step 1) using a mixture of steam and H2. At the end of this step, reactor regeneration, and the reactor is ready to undergo a new cycle.

In our studies, a 24 min, 4-bed-4 step cycle was investigated for the water-gas shift reaction. A H2- selective carbon molecular sieve membrane together with a CO2-selective hydrotalcite adsorbent, and a commercial Cu/Zn catalyst was used. Virtually 100% conversion is achieved during the reaction step, while simultaneously 100% of CO2 is being captured during this step. Since the membrane excludes CO, the hydrogen product in the permeate side is highly pure, and ready to use in a fuel cell. A more detailed description of the characteristics of the HAMR cyclic process will be discussed during the conference presentation.

Acknowledgement: The support of the US Department of Energy and NASA is gratefully acknowledged.

1.Y. Choi, H. Stenger, J. Power Source, 124, 432 (2003).

2.N. Darwish,N. Hilal, G. Versteeg, B. Heesink, Fuel, 83, 409 (2003).

3.Z. Liu, H.Roh, S.Park, , J. Power Sources, 111, 83. ( 2002)

4.T. A. Semelsberger, L. F. Brown, R. L. Borup, M. A. Inbody, Int. J. Hyd. Energ. 29, 1047. (2004)

5.B. Park, Ph.D. Thesis, University of Southern California, Los Angeles, California, (2001)

6.B. Park, T.T. Tsotsis, Chem. Eng. Proc. 43, 1171.(2004)

7.B. Fayyaz, A. Harale, B.G. Park, P.K.T. Liu, M. Sahimi, and T. T. Tsotsis, Ind. Eng. Chem. Res., 44 (25), 9398 -9408, (2005)

8.A. Harale, H. Hwang, P.K. Liu, M. Sahimi, and T.T. Tsotsis, Chemical Engineering Science 62:4126- 4137(2007)

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Hybrid and Novel Processes II – 2

Thursday July 17, 3:00 PM-3:30 PM, Kaua’i

Nanoparticle-Enhanced Microfiltration for Low Energy Metal Removal from Water.

A. Jawor (Speaker), University Of California Los Angeles, Los Angeles, California, USA - [email protected] E. Hoek, University Of California Los Angeles, Los Angeles, California, USA

Polymer-enhanced ultrafiltration (PEUF) is highly effective for selectively removing metal ions from water, but this process is difficult to implement in practice because polymer gel formation and pore plugging lead to severe, often irreversible flux decline. Recently, dendritic polymers (a.k.a., dendrimers) have been proposed as a high-binding capacity, low-fouling alternative to traditional polyelectrolytes. However, dendrimers are very expensive and require use of tight, ultrafiltration membranes. Nanoparticle-enhanced microfiltration (NEMF) is a hybrid membrane process, like PEUF, where a target contaminant selectively reacts with nanoparticles added to a mixed reactor. Contaminant-nanoparticle complexes are removed using low-pressure microfiltration membranes.

In this study, we evaluate nanoparticle-enhanced microfiltration using inorganic nanoparticles. Our objective is to demonstrate selective removal of divalent metal cations from simple and complex electrolytes through addition of metal-binding nanoparticles followed by microfiltration. As a first step towards testing this concept, we evaluate a traditional polyelectrolyte (polyacrylic acid), a succinic and carboxylic acid functionalized PAMAM dendrimers, and a NaA zeolite nanocrystals as metal-binding agents in combination with various microfiltration and ultrafiltration membranes. Electron microscopy, light scattering, particle electrophoresis, direct titrations, and contact angle analyses are used to characterize nanoparticle size, shape, hydrodynamic radius, zeta potential, charge density, and surface energy, respectively. Preliminary metal-binding experiments are performed to elucidate nanoparticle binding kinetics, capacity and strength (i.e., reversibility) using various divalent metal ions (Ca2+, Mg2+, Ba2+, Sr2+, Cd2+). Nanoparticle rejections and flux decline are determined using polysulfone- based UF and MF membranes ranging from molecular weight cut-off (MWCO) of 5 kD up to a characteristic pore size of 100 nm. Mechanisms of membrane fouling by polymers, dendrimers, and nanocrystals are elucidated by fitting flux decline data with classical blocking filtration models. Clean and fouled membrane surfaces are analyzed by SEM/EDX to confirm morphology and composition of fouling layers formed. Additional membrane characterization includes pure water permeability and zeta potential by electrolyte filtration experiments, plus surface roughness and energy via AFM and contact angle analyses.

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In the presentation, we will present results from membrane filtration experiments used to characterize (1) metal ion sequestration by the different binding agents, (2) optimal membrane MWCO/pore size for nanoparticle filtration, and (3) the extent, mechanisms, and reversibility of membrane fouling by each nanoparticle.

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Hybrid and Novel Processes II – 3

Thursday July 17, 3:30 PM-4:00 PM, Kaua’i

Crystallization in Hollow Fiber Devices

D. Zarkadas (Speaker), Schering Plough Research Institute, Union, New Jersey, USA K. Sirkar, New Jersey Institute of Technology, Newark, New Jersey, USA - [email protected]

Membrane based crystallization has recently attracted interest as an alternative crystallization technique. Both hollow fiber and flat membrane devices have been tested. This paper focuses on the use of hollow fiber devices for cooling and antisolvent crystallization. Their compactness, high heat and mass transfer volumetric efficiency, scalability and ease of operational control makes hollow fiber devices ideal for the creation of homogeneous supersaturation conditions and hence for tight crystal size distribution (CSD) control.

Cooling crystallization was studied in hollow fibers with solid, nonporous walls. These devices are extremely efficient heat exchangers with a relatively flat radial temperature profile inside the hollow fibers. Therefore, they can serve as standalone crystallizers or supersaturation creation devices in combination with a completely stirred tank. The performance of hollow fiber devices as standalone crystallizers for aqueous KNO3 was characterized by broader CSDs and lower reproducibility compared to literature data from Mixed Suspension Mixed Product Removal (MSMPR) crystallizers due to generation of a large number of fines causing slow filtration and localized growth on the filters. However, when the hollow fiber module was used for supersaturation creation in combination with a stirred tank, it yielded narrow and reproducible CSDs with mean sizes between 100-150 μm, 3-4 times lower than MSMPR crystallizers. Also, 90% of the crystals were smaller than 370 μm compared to 550-600 μm for MSMPR crystallizers. Further, the number of crystals generated per unit volume was 2-3 orders of magnitude higher.

When hollow fiber devices were used as supersaturation creation devices in combination with a static mixer for cooling crystallization of paracetamol in ethanol, it was illustrated that the solution can be kept stable even 30-40oC below published metastable zone values. This leads to the achievement of very high nucleation rates and hence small crystal sizes. The nucleation rates were 2-4 orders of magnitude higher than values obtained for potassium nitrate and salicylic acid and reached values encountered only in impinging jet crystallization. A qualitative comparison with existing literature data showed that the CSD was confined to smaller sizes and a narrower range. Finally, a linear relationship between the mean crystal size and the cooling medium temperature

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was observed, indicative of the simplicity of CSD control available in solid hollow fiber devices.

Porous hollow fiber antisolvent crystallization was tested for a well studied biological molecule, L-asparagine monohydrate. The antisolvent for the aqueous solution was isopropanol. The process proved to be successful despite the fact that the geometrical design of the membrane hollow fiber crystallizers used was not optimal. Mean crystal sizes between 34-86 μm and 33-40 μm were obtained respectively in standalone membrane hollow fiber crystallizers (MHFC) and their combinations with completely stirred tanks. The CSD was confined below 150 μm for the former and 70 μm for the latter, levels that are sufficient for most pharmaceutical crystalline products, for which bioavailability and formulation concerns dictate the desired CSD. In addition, porous hollow fiber devices achieved 1-5 orders of magnitude higher nucleation rates compared to batch stirred crystallizers. Considerable improvements can be obtained by carefully designing membrane hollow fiber crystallizers.

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Hybrid and Novel Processes II – 4

Thursday July 17, 4:00 PM-4:30 PM, Kaua’i

Selectivity between Potassium, Sodium and Calcium Ions in Synthetic Media and Juice Media Using Wafer Enhanced- Electrodeionization

T. Ho (Speaker), University of Arkansas, Arkansas, USA R. Cross, University of Arkansas, Arkansas, USA J. Hestekin, University of Arkansas, Arkansas, USA - [email protected] A. Kurup, University of Arkansas, Arkansas, USA

Wafer enhanced electrodeionization (WE-EDI) is a new technology that has been shown to removal ions from fermentation broths to very dilute levels (Arora et al., 2007). The novelty in the process is producing unique wafers, that transport ions, and incorporating these into an electrodialysis stack. Although the technology has been shown to be viable for dilute ion separations, areas such as selective separations, wafer enhancement, and ion exchange bead selection have not been explored. This paper is focused on the removal of sodium ion in the present of other competing ions such as potassium and calcium. The purpose is to produce low sodium juice for health purpose especially for low sodium tolerance patients. Using WE-EDI technology would allow controlling the selectivity of the ions. Moreover, WE-EDI will provide and attractive alternative to the use of bipolar membranes in electrodialysis. The WE-EDI technology has been shown to increase the performance of the membranes by increasing the transport of ions through the system. For instance, early studies of removal of sodium and potassium show up to a 40% reduction of power under certain conditions. WE-EDI also may increase the life time of the membrane especially in high complex media such as juice by allowing water dissociation on the surfaces of the resin beads instead of on the surface of the membranes, which is violent and hard on the surface layer. This paper addresses the characteristics of wafer: porosity and capacity with different composition. We also propose a mathematical model that provides a good prediction for product quality, especially for low sodium juice production. The selectivity difference between sodium, potassium, and calcium will be evaluated in order to optimizing the process performance. The experimental will ensure the accuracies of the model as well as provides the reason why WE-EDI technology has an economic advantage in comparison with the bipolar membrane electrodialysis or conventional electrodialysis.

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References

Arora, M.B., J.A. Hestekin, S.W. Snyder, E.J. St. Martin, M.I. Donnelly, C. Sanville-Millard and Y.J. Lin, ‘The Separative Bioreactor: A Continuous Separation Process for the Simultaneous Production and Direct Capture of Organic Acids’, Separation Science Technology, 42, 2519-2538, 2007.

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Hybrid and Novel Processes II – 5

Thursday July 17, 4:30 PM-5:00 PM, Kaua’i

Capillary ElectroChromatography and Membrane Technology: Merging the Advantages

K. Kopec (Speaker), University of Twente, The Netherlands D. Stamatialis, University of Twente, The Netherlands - [email protected] M. Wessling, University of Twente, The Netherlands

Introduction

Capillary ElectroChromatography (CEC) is a separation technique that is a hybrid of capillary electrophoresis (CE) and high performance liquid chromatography (HPLC). The flow of mobile phase is driven through the column by an electric field (a phenomenon known as electroosmosis) generated by applying a high voltage across the column. Application of electrical current, rather than pressure, and presence of a stationary phase result together in fast separations that combine the efficiency of capillary electrophoresis and the selectivity of liquid chromatography. CEC with its precision, accuracy and possibility of separation of complex mixtures is an eligible technique for dealing with biomolecules (proteins, peptides) and pharmaceuticals. Currently three types of columns are used in capillary electrochromatography: in-situ polymerized monoliths, capillaries packed with particles and capillaries with inner coatings (open tubular). In each case, the stationary phase is incorporated into fused silica capillary and in each case manufacture of a CEC column is a time consuming and expensive process.

Experimental

In our approach, membrane technology is employed to produce porous polymer fibers and apply them as stationary phase in CEC. Full, as well as, small bore-fibers, both with uniform porosities are manufactured via phase inversion by immersion precipitation spinning. In this work, fibres are prepared from two different blends: poly-ether-sulphone (PES) with sulphonated poly-ether-ether-ketone (S-PEEK), and polyimide P84 with S-PEEK. The sulphonation degree of S-PEEK and the blend ratios of PES/S- PEEK and P84/S-PEEK are tailored to achieve fibre with high charge density and mechanical stability. The sulphonic functional groups of S-PEEK, which are ionized over a wide range of pH, generate high electroosmotic flow.

Results and conclusions

The produced fibres have outer diameters ranging from 400 to 1000 micron, small bores up to 60 micron and sizes of the pores from 0.5 to 15 micron. The

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performance of fibers is analyzed and compared with commercially available CEC columns in a home-built CEC set-up enabling testing of fibers with various diameters and lengths. The characteristics of the polymeric fibers are not inferior to the current stationary phases introduced into fused silica. This, together with the ease and low cost of fabrication makes the polymer fiber competitive to the silica capillary and allows scaling up of the separation process into massively parallelized fashion.

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Hybrid and Novel Processes II – 6

Thursday July 17, 5:00 PM-5:30 PM, Kaua’i

Chitosan Chiral Ligand Exchange Membranes for Sorption Resolution of Amino Acids

H. Wang, Sichuan University, Sichuan, China L. Chu (Speaker), Sichuan University, Sichuan, China - [email protected] R. Xie, Sichuan University, Sichuan, China C. Niu, University of Saskatchewan, Saskatoon, Canada M. Yang, Sichuan University, Sichuan, China H. Song, Sichuan University, Sichuan, China

The concept of chiral ligand exchange is employed in the present study to achieve the chiral resolution of tryptophan (Trp) enantiomers by using chitosan (CS) membrane in a sorption resolution mode and copper(II) ion as the complexing ion. CS porous membranes are prepared by freeze-drying method (CS-LT) and sol-gel process at high temperature (CS-HT) respectively to investigate their sorption resolution characteristics. The proposed CS chiral ligand exchange membranes exhibit good chiral resolution capability. Meanwhile the sorption selectivity of the CS membranes is found to be reversed from L-selectivity at low copper(II) ion concentration to D-selectivity at high copper(II) ion concentration, which is attributable to the competition between the copper(II)-Trp complex behavior on the CS membrane and in the bulk solution as well as the stability difference between the copper(II)-L-Trp and copper(II)-D-Trp complexes. Moreover, the CS-HT membrane shows better performance with respect to both sorption selectivity and sorption capability than the CS-LT membrane, which is resulted from its more amorphous structures compared with the more crystalline structures of the CS-LT membrane.

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Membrane Fouling III - RO & Biofouling – 1 – Keynote

Thursday July 17, 2:15 PM-3:00 PM, Maui

Biofouling of Spiral Wound Nanofiltration and Reverse Osmosis Membranes: A Feed Spacer Problem

J. Vrouwenvelder (Speaker), Wetsus, Delft University of Technology, Delft, The Netherlands - [email protected] D. Graf von der Schulenburg, University of Cambridge, Cambridge, United Kingdom J. Kruithof, Wetsus Centre of Excellence for Sustainable Water Technology, Leeuwarden, The Netherlands M. Johns, University of Cambridge, Cambridge, United Kingdom M. Van Loosdrecht, Delft University of Technology, Delft, The Netherlands

Biofouling - growth of biomass, i.e. biofilms - is a major fouling type in nanofiltration and reverse osmosis membrane systems. Biofouling increases the pressure drop, thereby increasing the process costs [1,2]. In spiral wound membrane elements, two types of pressure drops can be discriminated: the feed spacer channel pressure drop and the trans membrane pressure drop. The trans membrane pressure drop is related to the membrane flux (permeation rate).

The objective of this study was to determine (i) the effect of biofouling on the feed spacer channel pressure drop and trans membrane pressure drop and (ii) the role of feed spacer on the pressure drop.

The development of feed spacer channel pressure drop and biofouling was investigated with monitors (named membrane fouling simulators [3]), single membrane element test rigs, a pilot and a full scale membrane filtration installation, operated with NF and RO membranes with and without permeate production. Additionally, the development of pressure drop and biofouling was determined in monitors without feed spacer. The feed water used for the laboratory studies was tap water with or/and without dosage of biodegradable compounds to stimulate biofouling. The development of fouling was monitored by (i) the pressure drop, (ii) in-situ real-time non- destructive observations such as nuclear magnetic resonance (NMR [4]) and using the sight glass of the membrane fouling simulator and (iii) analysis of coupons sampled from the monitor or membrane modules. The parameters determined were adenosine triphosphate (ATP), total direct cell counts and total organic carbon (TOC).

Biofilm accumulation affected the feed spacer channel pressure drop without influencing the trans membrane pressure. The same feed channel pressure drop development in time was observed in nanofiltration and reverse osmosis membrane modules. Apparently, the membrane type was not influencing biofouling development. From the observations it can be concluded that the pressure drop increase due to biofouling is a feed spacer problem. This

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conclusion is based on (i) in-situ observations on the fouling accumulation and velocity distribution profiles using NMR, (ii) in-situ visual observations on the fouling accumulation using the monitor sight glass and (iii) the development of pressure drop and biomass in monitors with and without feed spacer.

In summary, biofouling is a feed spacer problem. The membrane fouling simulator in combination with NMR measurements are suitable measurement tools for in-situ, real-time and non-destructive studies of the biofouling formation process in nanofiltration and reverse osmosis membranes. Biofouling research should be focused on the feed spacer (channel) so that biomass accumulation has low(er) impact on the feed channel pressure drop.

Literature

[1] Ridgway, H.F. (2003). Biological fouling of separation membranes used in water treatment applications, AWWA research foundation.

[2] Characklis, W.G., Marshall, K.C. (1990) Biofilms. John Wiley & Sons, New York.

[3] Vrouwenvelder, J.S. van Paassen, J.A.M., Wessels, L.P., van Dam A.F., Bakker, S.M. (2006). The Membrane Fouling Simulator: a practical tool for fouling prediction and control. Journal of Membrane Science. 281, 316- 324.

[4] Graf von der Schulenburg, D.A., Vrouwenvelder, J.S., Creber, S.A., Van Loosdrecht, M.C.M., Gladden L.F., Johns, M.L. (to be submitted). Nuclear Magnetic Resonance microscopy studies of membrane biofouling.

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Membrane Fouling III - RO & Biofouling – 2

Thursday July 17, 3:00 PM-3:30 PM, Maui

Microbial-Sensing Membranes Functionalized with a Temperature Sensitive Polymer Film

C. Gorey (Speaker), University of Toledo, Toldeo, Ohio, USA - [email protected] I. Escobar, University of Toledo, Toldeo, Ohio, USA C. Gruden, University of Toledo, Toledo, Ohio, USA

The presence of microorganisms in feed water can further exacerbate fouling due to the accumulation of microorganisms onto the membrane surface and on the feed spacer between the envelopes, or biofouling. Microorganisms transported to the membrane element can attach to the feed side of the membrane and the spacer. Attachment depends on Van der Waals forces, hydrophobic interactions and electrostatic interactions between the microorganisms and the surface. Biofouling control has been attempted via biocide additions; however, while a biocide may kill the biofilm organisms, it usually will not remove the biofouling layer, and may cause bacteria that survive disinfection to potentially become more resistant. Therefore, bacterial detection is essential in determining biofouling potential. In situ detection of bacteria in membrane-based water treatment systems is critical since biofouling can significantly impact membrane efficiency. Moreover, there is a keen interest in tracking and eliminating potential pathogens in these systems. With very few exceptions, techniques for specific detection of bacteria in aqueous systems are based on membrane filtration followed by culturing and phylogenetic or functional analysis. Direct detection strategies, which eliminate the bias introduced in culture-based methods, are gaining in popularity. Biorecognition molecules have been designed to label characteristic artifacts (e.g., exocellular proteins, fatty acids) and genomic material (e.g., nucleic acids). Methods based on the detection of antibodies against microbial specific exocellular proteins (antigens) are characterized by their simplicity, rapid response, and financial viability. For specific detection, antibodies (Ab) can be immobilized on surfaces for immunocapture of target bacterial species and subsequent separation of the target species from complex matrices. Antibodies have been applied to target a wide range of bacteria in various sample types including natural waters and sediments. Support media for antibody-based sensors have included the surfaces of magnetic beads, microplates, and glass slides. We propose to produce a fouling-resistant membrane by attaching a stimuli-responsive polymer film on the surface, which offers the potential to collapse or expand the polymer film. The phase change arises from the existence of a lower critical solution temperature (LCST) such that the polymer precipitates from solution as the temperature is increased. This temperature is determined to be where the mass is changing the fastest. This capability can be exploited to control

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adsorption/desorption. We then will use the polymer film to act as the support medium for bacterial sensing. To our knowledge, this is the first application of conjugated polymers attached to membranes for bacterial sensing. While this project will focus on developing fouling resistant membranes with in-situ bacterial sensing, this technology can easily be translated to small membrane coupons. The polymers being studied for this application are Hydroxypropyl Cellulose and N-Isopropylacrylamide and have LCSTs in a usable temperature range. Attachment to the Cellulose Acetate surface has been studied using a Primary method, which involves building the film from the surface. The latest method we have been attempting deals with the Secondary method, this synthesis works by building the film first and then attaching it to the surface. Wetcell Atomic Force Microscopy allows us the image the surface and do roughness analysis while under different temperatures in an aqueous environment. This means we can detect how rough the surface is at the low temperatures, where the film should be extended; and at high temperatures, where the film should be collapsed. The method of immunocapture uses antibodies and we attach those antibodies using a carbodiimide acting as a zero-length linker to connect a hydroxyl group from the HPC to the carboxyl group on the antibody. So far only work has been done with HPC in this area. Exposure of the completely modified membrane to bacteria has yielded successful capture of said bacteria which can be visualized using fluorescence.

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Membrane Fouling III - RO & Biofouling – 3

Thursday July 17, 3:30 PM-4:00 PM, Maui

Modification of Microfiltration Membranes: Implications for Biofouling, Flux Recovery and Antibacterial Properties

R. Malaisamy (Speaker), Howard University, Washington, District of Columbia, USA - [email protected] D. Berry, University of Michigan, Ann Arbor, Michigan, USA D. Holder, University of Michigan, Ann Arbor, Michigan, USA L. Raskin, University of Michigan, Ann Arbor, Michigan, USA L. Lepak, Cornell University, Ithaca, New York, USA K. Jones, Howard University, Washington, District of Columbia, USA

Biofouling remains one of the most problematic issues surrounding membrane based water treatment processes. Biofouling is likely to occur whenever microorganisms are present in the feedwater. It is difficult to remove all microorganisms prior to membrane filtration, and disinfectants have been shown to deteriorate many membrane surfaces. A lot of research has been performed on modifying membrane surfaces to prevent organic, inorganic and colloidal fouling, however research on membrane modification for prevention of biofouling is rather limited. We grafted an antibacterial quaternary ammonium acrylic polymer onto polyethersulfone (PES) microfiltration membranes. A quaternary salt of acrylic acid derivative, [2-(Acryloyloxy)ethyl]trimethylammonium chloride (AETMA) was taken and the polymerization on the membrane surface was carried out under a high energy UV radiation. We confirmed the chemical modification on the membrane using ATR FT-IR spectroscopy by identifying a peak at 1730 cm-1 corresponding to the carbonyl group of the co-polymer. The degree of grafting was found to be proportional to the monomer concentration and the time of irradiation. The streaming potential measurements showed that the surface charge of the parent membrane was reversed from negative to positive and the absolute value of zeta potential was almost constant irrespective of the degree of modification. The water contact angle values reduced gradually when the degree of grafting increased, showing that the membranes become more and more hydrophilic. The permeability and pure water flux declined proportionate to the degree of grafting and the scanning electron microscopic pictures illustrated that the surface of the membrane and pores were covered by the co-polymer that caused the flux decline. When the unmodified membranes during filtration were subjected to a pure culture of Escherichia coli as the model foulant, the permeate flux declined rapidly to about 30% of the initial flux, and was recovered only to 70% upon hydraulic cleaning and completely recovered only after chemical cleaning. For the modified membranes, the permeability declined gradually as the degree of grafting increased. However, during filtration with the E. coli suspension, the modified membranes did not undergo any flux decline (irrespective of the degree of grafting), and the flux increased over 100%

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after cleaning. Both hydraulic and chemical cleaning resulted in an unexpectedly large flux improvement. In order to determine whether or not the modification changed the basic membranes structure, both morphological and surface characterizations by FTIR were conducted and the results confirmed the stability of the co-polymer. Measuring the contact angle showed an improvement in hydrophilicity after the fouling studies, which may have caused the flux improvement. Another objective of this study was to accomplish lysis of bacterial cells to further reduce the likelihood of bacterial growth on the membranes. Fluorescence microscopic investigations showed that interactions on the surface of the AETMA modified membrane surface damaged the bacterial cells. These AETMA modified PES membranes when compared with acrylic acid modified ones with the same extent of modification, perform better in terms of permeate flux, recovery, and anti-bacterial activity.

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Membrane Fouling III - RO & Biofouling – 4

Thursday July 17, 4:00 PM-4:30 PM, Maui

Role of Seawater Chemistry in Algal Biopolymer Fouling of Seawater RO Membranes

X. Jin (Speaker), University of California Los Angeles, Los Angeles, California, USA - [email protected] E. Hoek, University of California Los Angeles, Los Angeles, California, USA

A major fouling concern in seawater reverse osmosis (SWRO) plants is the increased biomass generated during algal blooms. Algae, bacteria, and their exudates are present in high concentrations, and thus, have the potential to foul RO membranes. Although, membrane fouling by colloids and dissolved organics has been studied extensively for brackish and wastewater applications, fouling behavior may be very different in seawater due to the high ionic strength and suppression of electrical double layer interactions. We hypothesize that short- range interfacial interactions will play a critical role in determining the rate and extent of SWRO membrane fouling and that seawater chemistry will strongly impact foulant-membrane interfacial interactions. As a first step towards understanding the role of seawater chemistry in SWRO membrane fouling, we have conducted a study of SWRO membrane fouling by algal biopolymers.

Commercially available SWRO membranes - FilmTec SWHR (Dow Chemicals, Minneapolis, MN) and SWC3+ (Hydranautics, Oceanside, CA) - are used as model SWRO membranes. The two membranes were selected because they represent a relatively hydrophobic, rough membrane with significant carboxylic acid functionality at its interface (Hydranautics SWC3+) and a relatively hydrophilic, smooth membrane with relatively little carboxylic acid functionality at its interface (FilmTec SWHR). The former is expected to be more fouling prone due to attractive acid-base interactions and its rough, carboxylic acid rich interface. The latter membrane is expected to be relatively resistant to fouling due to repulsive acid-base interactions and its relatively smooth, non- carboxylated interface.

Accelerated fouling experiments are carried out in a bench-scale SWRO simulator with 6 parallel flat-sheet membrane cells. Alginic acid - an acidic hetero-polysaccharide excreted by Brown algae - is spiked into synthetic seawater solutions with constant total dissolved solid (TDS) concentrations of 32 g/L, but varied concentrations of major cations (e.g., sodium, magnesium, calcium). In addition, a real seawater matrix (Instant Ocean®) was also evaluated. Water flux and conductivity rejection are tracked with time. At the end of fouling experiments, cleaning is performed first using laboratory de-ionized (DI) water, followed by a 5 mM EDTA solution adjusted to pH 11 by NaOH

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addition. Extensive characterization of clean and fouled membranes and alginic acid are performed to evaluate material compositions, functionalities, physicochemical properties, and alginate-membrane interfacial interactions.

Results from fouling experiments confirm that specific ions present in seawater dramatically impact the rate, extent, and reversibility of flux decline. Alginic acid does not cause much membrane fouling in NaCl solutions with pH of 6, whereas it causes significant fouling in the real seawater matrix adjusted to pH 6. In addition, there is significant fouling in NaCl solutions spiked with divalent cations (Mg2+ and Ca2+) at concentrations identical to those in real seawater. However, the effect of Ca2+ on flux decline is much more pronounced than that of Mg2+. The initial rates of flux decline (dJ/dt) for both membranes decrease as: pure NaCl > Instant Ocean, pH6 > NaCl + MgCl2 > NaCl + CaCl2. Physicochemical characterization reveals the interfacial free energy of adhesion between both membranes and alginic acid follow the same order of decline: pure NaCl > Instant Ocean, pH6 > NaCl + MgCl2 > NaCl + CaCl2, where a higher free energy indicates smaller propensity for adhesion (or greater fouling resistance). In all solution chemistries, SWC3+ appears more fouling prone than SWHR because of its more hydrophobic, rough surface, which produces attractive interfacial interactions.

Flux decline due to alginate fouling in the absence of Ca2+ ions is almost completely reversible using only DI water; however, DI water is almost completely ineffective at recovering the initial flux if Ca2+ ions are present. Cleaning with an alkaline EDTA solution almost completely recovers the initial flux, thus providing more evidence for the specificity of calcium-mediated fouling. For the membrane samples fouled in the real seawater matrix, permeate flux is poorly recovered after cleaning even when EDTA is employed, suggesting that the more complex composition of seawater produces a more complex fouling problem. In all cases, the initial flux of SWHR is more completely recovered by cleaning than that of SWC3+. We believe this is due to its PVA coating, which reduces calcium-carboxylate complex formation between alginate and the polyamide material.

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Membrane Fouling III - RO & Biofouling – 5

Thursday July 17, 4:30 PM-5:00 PM, Maui

Effect of surface charge and pH on fouling and critical flux of MF membranes during protein filtration

Jochen Meier-Haack (Speaker), Leibniz Institute of Polymer Research Dresden, Dresden, Germany - [email protected]

Although subject to research for decades, fouling is still one of the major limiting factors in membrane applications. Numerous methods have been suggested to overcome this drawback, like crossflow filtration, backflushing, air sparging, all of them in combination with chemical cleaning. However many of these techniques imply off-production cycles, resulting in lower yield, shorter life-time of membranes and therefore higher costs. In the mid-nineties Field et al. introduced the concept of the -critical flux [1, 2] and which has been subject of a review recently [3]. It defines a permeate flux below a critical value - the critical flux - where no irreversible fouling occurs. The critical flux is determined by several factors including hydrodynamic forces introduced by the crossflow velocity and the transmembrane pressure, electrostatic interaction between feed components and the membrane surface and others [3]. Although mainly important for large molecules, we have focused our work on the effect of surface charges on fouling and critical flux.

In static (non-filtration) adsorption experiments we observed a strongly reduced protein adsorption at the surface in the case of repulsive electrostatic forces between the membrane surface and feed components and vice-versa [4]. The same effect was reported in dead-filtration using surface modified MF-membranes [5]. We now extended our investigations on the effect of surface modification on the critical flux. Surface modified microporous PP membranes were obtained by grafting polyacrylic acid onto the surface using a so-called macroinitiator [6, 7]. These modified membranes showed a strong influence of pH on the filtration properties (stimuli-response membranes). The surface charge was reversed by adsorption of a polycation (PDADMAC) onto the graft-layer. Although the total amount of modificator on the membrane surface was increased, a slight flux enhancement (at constant pressure) was observed compared to the "one-layer" membrane. Simultaneously the response on pH change was reduced dramatically, but still observable. Upon the adsorption of a third polyelectrolyte layer (PAAc) the response to pH change was recovered to a small extent while the permeate flux at constant pressure was unchanged (20 l/m2h at 1 bar) compared to the two-layer membrane. The surface modification along with the introduction of surface charges has also a strong effect on the critical flux. While for the unmodified membrane a critical flux of 20 l/m2h was

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detected, this value increased with increasing number of polyelectrolyte layers adsorbed to the membrane surface in the case when the feed components (here bovine serum albumin) and the surface are equally charged (repulsive electrostatic forces). For a three-layer membrane (PAAc/PDADMAC/PAAc) a critical flux > 60 l/m2h was determined. In the case of attractive electrostatic forces a dramatic fouling was observed.

[1] R. W. Field; D. Wu; J. A. Howell; B. B.Gupta; J. Membr. Sci. 100, 259 (1995)

[2] J. A: Howell; J: Membr. Sci. 107, 165 (1995)

[3] P. Bacchin, P. Aimar, R. W. Field; J. Membr. Sci. 281, 42 (2006)

[4] M. Müller et al.; Macromol. Rapid Commun. 19, 333 (1998)

[5] T. Rieser et al.; ACS Symposium Series 744, Edts. I. Pinnau. B. D. Freeman; ACS, Washington (1999), p. 189

[6] T. Carroll, N. A. Booker, J. Meier-Haack; J. Membr. Sci. 203, 3 (2002) [7] J. Meier-Haack, S: Derenko, J. Seng; Sep. Sci. Technol. 42, 2881 (2007)

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Membrane Fouling III - RO & Biofouling – 6

Thursday July 17, 5:00 PM-5:30 PM, Maui

Synthesis and Evaluation of Novel Biocidal Coatings to Reduce Biofouling on Reverse Osmosis Membranes

M. Hibbs (Speaker), Sandia National Laboratories, Albuquerque, New Mexico, USA - [email protected] C. Cornelius, Virginia Poytechnic Institute and State University, Blacksburg, Virginia, USA L. McGrath, Sandia National Laboratories, Albuquerque, New Mexico, USA S. Altman, Sandia National Laboratories, Albuquerque, New Mexico, USA S. Kang, Yale University, New Haven Connecticut, USA A. Adout, Yale University, New Haven Connecticut, USA M. Elimelech, Yale University, New Haven Connecticut, USA

Reverse osmosis (RO) is a membrane-based separation process that is commonly used in industrial applications such as desalination and waste-water treatment. The major problems associated with membrane-based separation processes include fouling and high pressure loss, which decrease the efficiency of the filtration while increasing operation costs. Quaternary ammonium compounds (QACs) are among the most widely used antibacterial agents and polymers containing ammonium salts have been shown to possess enhanced antibacterial activity with reduced toxicity and prolonged lifetimes. An RO membrane coated with such a polymer should prove resistant to biofouling and thus more efficient over its useful lifetime.

Novel ionomers have been prepared from a poly(arylene ether sulfone) with benzyl trialkylammonium groups randomly attached in a postpolymerization step. The alkyl chain lengths were varied among the different ionomers because this has been reported to be a crucial factor in establishing the biocidal activity of QACs. All of the polymers were soluble in alcohols with the aid of a surfactant and, unlike most polymers with quaternary ammonium groups, they were insoluble in water. However, they were hydrophilic and swelled in water, key features which allowed water to pass through them. The polymer solutions could be sprayed onto RO membranes to form thin coatings. Contact angle, streaming potential, and AFM interaction forces were measured for the coated surfaces. Testing for cell adhesion and antibacterial properties with E. coli showed that all of the coatings had significant biotoxicity. Results from accelerated biofouling tests in a cross-flow RO system will also be discussed.

Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-ACO4-94AL85000.

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Pervaporation and Vapor Permeation II – 1 – Keynote

Thursday July 17, 2:15 PM-3:00 PM, Moloka’i

Aromatics Control in Refining with Pervaporation

R. Harding, W.R. Grace & Co.-Conn., Columbia, Maryland, USA L. White (Speaker), W.R. Grace & Co.-Conn., Columbia, Maryland, USA - [email protected]

Benzene, toluene, and xylenes (BTX) are commodity chemicals produced in large volumes at refineries. Benzene, however, attracts regulatory interest due to a carcinogenic nature and also has numerous other unique chemical properties. We have seen that these aromatics (BTX) can interact strongly with pervaporation membranes. Given that aromatic selective membranes can selectively transport even low levels of benzene in pervaporation mode, Grace has been able to demonstrate that benzene levels can easily be reduced to less than 0.2% in refinery process streams. These new aromatic selective membranes, part of the Aromem(TM) class, are being applied to real world refining streams to selectively control benzene levels. This class of membranes, built upon the S-Brane(TM) technology platform, is ready for commercial testing.

S-Brane and Aromem are trademarks of W.R. Grace.

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Pervaporation and Vapor Permeation II – 2

Thursday July 17, 3:00 PM-3:30 PM, Moloka’i

Membrane Based Liquid Fuels Desulfurization Process for Point-of-Use Applications

D. Aagesen (Speaker), Intelligent Energy Inc., Long Beach, California, USA - [email protected] D. Swamy, Intelligent Energy Inc., Long Beach, California, USA

In order to address the growing concern over sulfur oxides and particulate matter emissions that adversely affect the environment and human health, Intelligent Energy (IE) has recently developed a unique fuel desulfurization technology. The process uses a polyimide membrane to fractionate fuels in a slip-stream point-of-use process. This technology can be applied to pre-treat fuels used by transportation equipment such as locomotives, large ships and other off-road equipment. The technology has the potential to significantly reduce pollutants thus directly improving the quality of life for nearly 25 percent of the world’s population. Furthermore, the technology can be used for the removal of dibenzothiophene and heavier refractory sulfur compounds from logistic fuels when placed upstream of adsorbent beds integrated with fuel cell auxiliary power units (APU). This leads to increased sorbent capacity and life.

This paper discusses the process configuration, engineering aspects, test data results from feedstock including Jet A, JP5, marine diesel oil (MDO) and highlights the commercial drivers and applications for the point-of-use system. Typical flux rates for the fuels tested ranged between 1-2kg/hr-m2 with sulfur reduction between 40-80% when stage-cuts (fraction of feed passed through the membrane) of 5-20% are obtained. The parasitic power requirement of the process can vary between 1-3% of the heating value of the cleaned fuel.

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Pervaporation and Vapor Permeation II – 3

Thursday July 17, 3:30 PM-4:00 PM, Moloka’i

Ion-containing Polyimide Membranes: A Way of Overcoming the Trade-off Permeability in Pervaporation ?

A. Jonquieres (Speaker), Nancy Universite, France - [email protected] M. Awkal, Nancy Universite, France R. Clement, Nancy Universite, France P. Lochon, Nancy Universite, France

Two international patents [1,2] and also recent results [3] have shown that polymeric membranes containing cationic groups are highly efficient for the removal of protic species (e.g. alcohols) from organic mixtures by pervaporation, with an important potential application for the purification of ethyl-tert-butyl ether (ETBE). By appropriate fiscal privileges for the past ten years, the European Union has been strongly inciting the large production of this alkyl ether from agricultural ethanol. Thanks to its specific advantages and its much better biodegradability than methyl-tert- butyl ether (MTBE), ETBE is currently considered as one of the most promising bio-fuels [4,5]. Nevertheless, its industrial synthesis process leads to an azeotropic mixture containing 20 wt % of ethanol which has to be removed for ETBE purification. If the former polymer membranes were well performing for this separation, the rather poor control of their chemical structure did not allow any detailed analysis about the influence of the cationic sites on their permeability.

Taking advantage of our former experience on polyimide copolymers for this separation [6], we recently developed the synthesis and characterization of 3 families of new ion-containing polyimide copolymers, with a control of the number of their cationic ammonium groups, the length of their alkyl side chain and the type of their counter- ions [7,8]. In this new communication, the membranes features of the 3 copolymer families will be discussed in terms of structure-property relationships on the basis of sorption and pervaporation results obtained for the separation of the azeotropic mixture EtOH/ETBE. In particular, it will be shown how simply changing the chemical structure of the cationic groups enabled to increase sharply permeability with a very low impact on selectivity, therefore overcoming the usual trade- off permeability/selectivity.

[1] H. Steinhauser, H. Brüschke, European Patent 0674940 B1 (1995).

[2] H. Steinhauser, H. Brüschke, US Patent 5,700,374 (1997).

[3] S. Touchal, D. Roizard, L. Perrin, Journal of Applied Polymer Science, Vol. 99 (2006) 3622.

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[4] H. Noureddini, Book of Abstracts, 219th ACS National Meeting, San Francisco, CA, March 26-30, 2000.

[5] R. Koenen, W. Puettmann, Grundwasser, Vol. 10 (2005) 227.

[6] A. Jonquieres, R. Clément, P. Lochon, Progress in Polymer Science, Vol. 27 (2002) 1803. (review)

[7] M. Awkal, A. Jonquières, G. Creffier, R. Clément, P. Lochon, Macromolecules, Vol. 37 (2004), 684.

[8] M. Awkal, A. Jonquières, R. Clément, P. Lochon, Polymer, Vol. 47 (2006), 5724.

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Pervaporation and Vapor Permeation II – 4

Thursday July 17, 4:00 PM-4:30 PM, Moloka’i

Study of the Effect of Framework Substitution on the Pervaporation of Xylene Isomers through MFI-type Zeolite Membranes

J. O'Brien-Abraham (Speaker), Arizona State University, Tempe, Arizona, USA J. Lin, Arizona State University, Tempe, Arizona, USA - [email protected]

Changing conventional xylene separation techniques such as extractive or azeotrophic distillation to continuous membrane processes has been the focus of much research in recent years. Specifically, the use of pervaporation to efficiently separate p-xylene (PX) from its isomers o-xylene and m-xylene (OX, MX) has gained significant attention. The success of such technology will rely on the ability of the membrane to provide significant flux and selectivity as well as good thermal and chemical stability under desired operating conditions. Molecular sieving inorganic membranes such as MFI-type zeolite show promise for this application. MFI-type zeolite membranes possess a microporous structure consisting of sinusoidal, elliptical channels (0.51 x 0.54 nm) interconnected with straight, circular channels (0.54 x 0.56 nm). Apertures of these sizes suggest that the membranes should be able to separate xylene isomers based solely on size selectivity given that PX is the only isomer small enough to enter the zeolite pores. However, for pervaporation applications saturated feed-side coverages cause high adsorption loadings of the MFI crystals. Under these conditions, the zeolite framework molecules shift to accommodate an entropically favorable packing of the PX molecules which leads to overall distortion of the MFI pores. This distortion allows for OX to be able to enter the pore structure causing competitive adsorption between the isomers. Ultimately, these PX-framework and PX-OX interactions reduce the ability of the membrane to separate the isomers via size selectivity. Our findings show that membrane performance is highly dependent on the relative concentration of isomers in the feed; the higher the PX concentration the lower the selectivity observed. Although high selectivity (~18) was observed at low PX concentration in the feed, it was not stable over time. The focus of this work is to use membranes with isomorphously substituted framework atoms in order to induce differences in both adsorption properties and membrane microstructure. Specifically, the metal ion Boron (B) was substituted into the MFI framework for Si. Boron was chosen because of its smaller size (relative to Si) which causes a reduction in the unit cell volume; it is speculated that this may induce some structural rigidity preventing the above mentioned affect of framework distortion at high PX loadings. Additionally, because B is a trivalent atom its presence in the microstructure will introduce acid sites that can affect the membrane adsorption properties. B-ZSM5 membranes were synthesized utilizing templated seeded growth methods and characterized via x-ray diffraction (XRD) and scanning electron microscopy (SEM). Single and multi-

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component (PX, OX) separation via pervaporation was performed at room temperature under a variety of feed compositions on both silicalite and B-ZSM5 membranes to evaluate to effectiveness of the substituted B in reducing the affects of framework flexibility and competitive adsorption at high loadings of PX.

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Pervaporation and Vapor Permeation II – 5

Thursday July 17, 4:30 PM-5:00 PM, Moloka’i

On the Unusual Transport Phenomena of Vapours in Amorphous Glassy Perfluoropolymer Membranes with High Fractional Free Volume

K. Friess, Institute of Chemical Technology, Prague, Czech Republic J. Jansen (Speaker), Institute on Membrane Technology, Rende, Italy - [email protected] E. Tocci, Institute on Membrane Technology, Rende, Italy E. Drioli, Institute on Membrane Technology, Rende, Italy

In this paper the gas and vapour transport through four different high fractional free volume amorphous glassy perfluoropolymers is studied. The idea of the paper is to correlate the experimental transport parameters with the fractional free volume (FFV) and with the molecular properties and activity of the different penetrants. In particular, the scope of the work is to fit our results with commonly used correlations, e.g. between the diffusion coefficient and the penetrant’s critical volume, and to study how these correlations change for chemically different species, which undergo for instance clustering and hydrogen- bonding, or for sterically different penetrants.

Amorphous glassy perfluoropolymers are known for their good film forming properties, high thermal and chemical stability, low tendency to swelling, insolubility in common organic solvents and their strong hydrophobic character. All such properties make them interesting for wet gas treatment where conventional polymers might suffer from plasticization by condensable species or chemical attach in corrosive environment. In spite of the low swelling, these polymers are nevertheless remarkably permeable to some organic vapours because of the high interconnected FFV, and therefore they have a certain potential for specific organic-organic separations, reason for the present study.

Samples of flat membranes from copolymers of 2,2- bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole with tetrafluoroethylene (Teflon AF®) and 2,2,4- trifluoro-5-trifluorometoxy-1,3-dioxole with tetrafluoroethylene (Hyflon® AD) were prepared by solution casting, using 1-methoxy- nonafluorobutane as the solvent [1]. Samples were left overnight to allow slow evaporation of most of the solvent and the films were further dried in a vacuum oven.

The permeability of the membranes was tested at 25°C in a fixed volume-pressure increase instrument for a series of different gases and vapours. The diffusion coefficients of the penetrants were determined from the transient behaviour (time lag method) and the permeability was calculated from the steady state pressure increase rate. Assuming the validity of the solution-diffusion model, the solubility was determined indirectly by the simple relation S=P/D.

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Generally these results were in good agreement with the literature data determined mostly by sorption measurements [2-4].

A log-log plot of the diffusion coefficient vs. critical volume of the penetrant showed the commonly observed linear relationship for permanent gases and linear hydrocarbons. However, large differences were found between the trends of dissimilar species in molecular shape (e.g. linear vs. branched or ring structures) or in molecular interactions (e.g. inert molecules vs. polar or hydrogen bonding species which may exhibit clustering [4]). For instance, n-alcohols show a similar trend as n- alkanes, but their diffusion is nearly half an order of magnitude slower than that of alkanes with a comparable critical volume, or it is similar to alkanes which have nearly twice their crucial volume. Similarly, cyclohexane diffusion is over two orders of magnitude slower than hexane diffusion and MTBE is 200 times slower than diethylether. The anomalous behaviour of the lower alcohols is further illustrated by the highly unusual transient in the methanol and ethanol permeation curves, suggesting the presence of multiple diffusion coefficients.

The experimental results were discussed in terms of the penetrant’s molecular properties and the free volume of the polymers. For this purpose the free volume of the two Hyflon samples was studied by molecular dynamics (MD) simulations. Several independent atomistic bulk models were constructed for each sample and the cavity size distribution was investigated by the particle insertion grid method [5]. It will be shown that the molecular modelling approach offers important insight in the possible behaviour of the penetrants in the free volume elements of the polymer.

References

1. M. Macchione, J.C. Jansen, G. De Luca, E. Tocci, M. Longeri and E. Drioli, Polymer 48 (2007) 2619-2635.

2. R.S. Prabhakar, B.D. Freeman, I. Roman, Macromolecules 2004, 37, 7688-7697.

3. A.Yu. Alentiev, Yu. P. Yampolskii, V.P. Shantarovich, S.N. Nemser, J. Membr. Sci 126 (1997) 123-132.

4. A. Tokarev, K. Friess, J. Machková, M. `ípek, Yu. Yampolskii, J. Polym. Sci. Part B, 44 (2006) 832-844.

5. D. Hoffmann, M. Heuchel, Yu. Yampolskii, V. Khotimskii, V. Shantarovich, Macromolecules, 35 (2002) 2129.

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Pervaporation and Vapor Permeation II – 6

Thursday July 17, 5:00 PM-5:30 PM, Moloka’i

Pervaporation Performance of PDMS-grafted Aromatic Polyamide Membrane Exhibiting High Durability and Processability

C. Yun (Speaker), Tokai University, Kanagawa, Japan Y. Nagase, Tokai University, Kanagawa, Japan - [email protected]

Pervaporation is a promising membrane technique for the removal of organic molecules from their aqueous solutions. In earlier investigations, the pervaporation process was applied to separate alcohol by water-selective permeation through membranes, which has been already used in industries. However, it is more practical to separate alcohol by using an alcohol- permselective membrane, because alcohol is a minor component in the fermentation product. Furthermore, if a practical organic-permselective membrane is obtained, the pervaporation technique is expected to be an efficient method for the removal or the recovery of organic components from waste fluid or industrial drainage. To achieve the selective permeation of organic components in the pervaporation of aqueous solutions of organic liquids, it is very important to enhance the solubility of alcohol over water in a polymer membrane because of the higher diffusivity of water as compared with alcohol. In addition, the durability of the membrane against several organic solvents is more important, because the organic component was concentrated in the inert of the membrane during the permeation. A crosslinked polydimethylsiloxane (PDMS) membrane, has been known to show a selective permeation of alcohol at the pervaporation of an aqueous alcohol solution. Such a separation property of PDMS membrane is due to the high hydrophobicity of the membrane surface and the high permeability of vapors through the membrane. However, it is not a practical membrane because an ultrathin membrane to achieve a high flux cannot be prepared from the crosslinked material. Therefore, we have prepared some soluble PDMS- grafted copolymers having a rigid backbone component that showed an improved mechanical property and organic-permselectivity. In our previous work, we have developed a siloxane-grafted polyamide (PA-g-PDMS) by the polycondensation of 3,5-bis(4-aminophenoxy)benzyloxypropyl- terminated polydimethylsiloxane (BAPB- PDMS) and terephthaloyl chloride, which exhibited a high organic permselectivity in the pervaporation of aqueous organic liquid solutions with a stable permeation. However, in the case of PA-g-PDMS, when the reprecipitated polymers were filtered and dried in vacuo, they became insoluble in all solvents. In other words, this membrane possessed poor processability due to the chemical structure of the backbone component. In this study, a chemical modification of the main chain structure of PDMS- grafted polyamide has been investigated to enhance the processability of the copolymer, with maintaining the durability to organic components. For this purpose, the

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introduction of methyl groups into the main chain polyamide component was carried out, in which a new macromonomer, 3,5-bis(4-amino-3- methylphenoxy)benzyloxypropyl- terminated polydimethylsiloxane (BAMPB- PDMS) was synthesized instead of BAPB- PDMS. Generally, it has been known that the introduction of alkyl group into aromatic polyamides could achieve the improvement of their solubility. The polycondensation of BAMPB-PDMS with terephthaloyl chloride yielded the desired siloxane-grafted polyamide copolymers, MPA-g-PDMS. The copolymer membranes were prepared by solvent casting method, and the gas permeability and pervaporation property of these membranes were evaluated. PA-g-PDMS was insoluble in any solvents after the copolymer was dried in vacuo, however, MPA-g-PDMS was soluble in solvents, such as tetrahydrofuran, chloroform and dichloromethane, even after it was completely dried. Therefore, MPA-g- PDMS exhibited the higher processability than PA-g-PDMS. Then, the measurement of stress-strain behavior of copolymer membranes was carried out, and these copolymer membranes showed the high mechanical strength. The gas permeability property of PA-g-PDMS and MPA-g-PDMS membranes was as same as that of the PDMS cross-linking membrane for all of the gases. In addition, gas permeability of these membranes were increased as increase of PDMS segment length, and these values of MPA-g-PDMS were slightly higher than those of PA- g-PDMS containing the same PDMS segment length. From the results of pervaporation of the dilute aqueous solutions of organic solvents, it was found that both of PA-g-PDMS and MPA-g- PDMS exhibited the excellent permselectivity toward several organic solvents, such as alcohols, acetone, tetrahydrofuran, chloroform, dichloromethane and benzene with a high and stable permeation. Such a high selectivity for organic liquids would be due to the hydrophobic surface covered with PDMS segments and the high permeability of the PDMS continuous domain, which were confirmed by transmission electron macrography (TEM). Therefore, it is expected that MPA-g-PDMS membranes can be used effectively for the removal of organic solvents from their aqueous mixtures due to their properties of high mechanical strength, durability and processability.

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Desalination II – 1 – Keynote

Thursday July 17, 2:15 PM-3:00 PM, Honolulu/Kahuku

Memstill: A Near-Future Technology for Sea Water Desalination

C. Dotremont (Speaker), Keppel Environmental Technology Centre, Singapore - [email protected] B. Kregersman, Keppel Seghers Belgium NV, Williebroek, Belgium S. Puttemans, Keppel Seghers Belgium NV, Williebroek, Belgium P. Ho, Keppel Environmental Technology Centre, Singapore J. Hanemaaijer, TNO Science and Industry, The Netherlands

The Memstill development history started some 10 years ago at TNO Science and Industry - the Netherlands. In 2002, Keppel Seghers joined the R&D consortium. Ten years of development work resulted in a box module concept which is leakage-free, resistant to hot sea water and has a salt reduction factor > 10.000 in scaled-up modules of 300 m2 membrane area.

Memstill is a membrane-based distillation technique which makes use of hydrophobic membranes to separate sea water from pure distillate. In a countercurrent flow process, the cold sea water enters the module and takes up heat in the condenser channel through condensation of water vapour, after which a small amount of (waste) heat is added, and flows counter currently back via the membrane channel. Driven by the small added heat, water evaporates through the membrane, and is discharged as cold condensate. The brine is disposed, or further concentrated in a next module. A heat exchanger between the condenser and membrane envelop supplies the necessary heat to the module. Because a Memstill module houses a continuum of evaporation stages in an almost ideal countercurrent flow process, a very high recovery of evaporation heat is possible: Gained Output Ratios (GOR) of 15-30 are achievable.

This technology is especially attractive in case low grade waste steam or solar heat is available, i.e. top temperatures between 60 and 90 degrees Celsius and a temperature difference over the membrane/condenser of 5 to 10 degrees Celsius are already sufficient to drive the process. In other words, memstill is energy/CO2 - neutral and is driven by relatively small quantities (100 - 200 MJ/m3) of heat. If operated in a once pass through system, memstill operates at recoveries of 5- 10%, without any additives like acids and anti-scalants, producing high quality fresh water and a brine which is only 10% concentrated and with only 2 to 5 degrees Celsius increase in temperature, thus without any proven environmental damage.

A first pilot plant - equipped with the first generation of modules - was operated for 14 months in Singapore (March 2006 - June 2007). And although the intake of sea water at the Strait of Johor was of low quality, the pilot showed good

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separation quality (10 µS/cm) and module integrity; however flux performance and energy efficiency were still quite low.

A second pilot - equipped with the second generation of modules - operated for 4 months at E.ON Benelux - in the Port of Rotterdam, the Netherlands (October 2006 - January 2007) with promising results. A mean distillate flux of 2.7 l/h.m2 or a distillate flow of 800 l/h (300 m2) has been measured during the 4 months test trial. At start-up, an energy consumption of 120-150 MJ/m3 was registered, increasing over time likely due to some fouling.

Currently, this pilot is being revamped for a third field test at the waste incineration plant of AVR, again situated in the Port of Rotterdam, the Netherlands. New modules were manufactured and installed - allowing higher cross-flows and higher energy efficiency. In addition, this pilot trial will focus on fouling issues and is scheduled for the coming six months, starting from March 2008 onwards. Preliminary cost assessments for large scale desalination show that Memstill costs come close or even equal RO sea water desalination costs. Because significant improvement of performance and decreasing production costs can be expected in coming years, Memstill technology should be subject to a further cost reduction. In addition, future increasing cost discrepancy can be expected in favor of Memstill as electricity costs are assumed to rise steadily in the coming years.

In this presentation an overview of the main results and improvements based on previous & current pilot trials will be given. Performance data like flux, energy consumption, distillate quality and fouling will be discussed. Finally, an outlook on further development work, product improvement and the preparation of the commercialization will be briefly presented.

Acknowledgement The Memstill development was supported by the Netherlands E.E.T. program. The Memstill consortium comprises Keppel Seghers,TNO, EMF, WTH, Twente University, E.ON Benelux,Heineken International, Evides, Amsterdam Waternet. The Memstill development was also supported by the Public Utilities Board (PUB) and the National Environment Agency (NEA) of Singapore.

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Desalination II – 2

Thursday July 17, 3:00 PM-3:30 PM, Honolulu/Kahuku

Parameters Affecting Osmotic Backwash

N. Avraham, Grand Water Research Institute, Technion, Haifa, Israel A. Sagiv (Speaker), Grand Water Research Institute, Technion, Haifa, Israel C. Dosoretz, Grand Water Research Institute, Technion, Haifa, Israel R. Semiat, Grand Water Research Institute, Technion, Haifa, Israel - [email protected]

The Reverse Osmosis (RO) membrane cleaning process is of great interest to the desalination industry. The water volume needed for the backwash process and the time duration of the wash process are key parameters that must be considered in practice. Appropriate changes in feed and permeate applied pressures across the membrane for a given concentration difference enable a shift back and forth from the RO to the BW process with minimal intervention by the RO desalination process. Effects of different parameters, including operation pressure and salt concentration, were investigated experimentally in the present study. Experiments were carried out, measuring the wash volume as a result of different salt concentrations in the RO steady-state operation prior to the backwash experiment and at different pressures on both sides of the membrane. Results show that within the operated range of parameters, the wash volume is basically independent of the initial pressure difference. Yet, as expected, it is affected by the difference in concentrations across the membrane. It was found that the wash volume increases with the concentration differences at the lower range and decreases at the higher range. This result is explained by the two opposite flux mechanisms discussed in a previous study of zero BW applied pressure. The BW volume decreases with BW feed applied pressure, indicating a decrease in BW driving pressure. For a similar reason, the BW volume increases with increased permeate side pressure since it increases the BW driving pressure.

Results of the present study provide an experimental basis for further understanding the BW process under industrial conditions, and finding BW characteristics necessary for the efficient design of RO-based desalination plants.

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Desalination II – 3

Thursday July 17, 3:30 PM-4:00 PM, Honolulu/Kahuku

Fabrication of High Performance Dual Layer Hydrophilic-Hydrophobic Hollow Fiber Membranes for Membrane Distillation Process

S. Bonyadi (Speaker), National University of Singapore, Singapore T. Chung, National University of Singapore, Singapore - [email protected]

Hydrophilic-hydrophobic composite membranes have been considered as promising membrane configurations to be applied as membrane contactors, especially for flux enhancement in membrane distillation (MD) process. While there are several reports in the literature demonstrating the fabrication of these types of membranes in flat sheet geometries, however, there is no such report in case of hollow fibers. Furthermore, most of the proposed approaches are either expensive or inefficient in controlling membrane properties such as porosity and pore-size distribution. For the first time in this paper, co-extrusion has been applied as a novel approach to fabricate dual layer PAN (hydrophilic) - PVDF (hydrophobic) composite membranes. The effect of different non-solvents on the morphology of the PVDF membranes was investigated and it was found that weak coagulants such as water/methanol (20/80, w/w) can induce a three dimensional porous structure on PVDF membranes with high surface and bulk porosities, big pore size, sharp pore size distribution, high surface contact angle and high permeability but rather weak mechanical properties. In order to enhance the membranes mechanical properties, hydrophobic and hydrophilic clay particles were incorporated into the outer and inner layer dope solutions, respectively. It was also found that the incorporation of clay particles in the fibers inner layer reduces the shrinkage and reduces the delamination between the two layers considerably. The fabricated fibers were characterized through pore size distribution, gas permeation, porosity and contact angle measurement tests. Ultimately they were tested for desalination through a direct contact membrane distillation process and fluxes as high as 47 kg/m2hr, were achieved at 90 ºC. By carrying out some modifications on the fabricated fibers the obtained flux was increased to 70 kg/m2hr at 86 ºC, which is a superior flux compared to all the data reported in the literature for hollow fiber membranes so far. The details regarding the conducted modifications are under review by the AIChE Journal.

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Desalination II – 4

Thursday July 17, 4:00 PM-4:30 PM, Honolulu/Kahuku

A New Niche for Electrodialysis: Improving Recovery from RO Desalination

D. Lawler (Speaker), The University of Texas at Austin, Austin, Texas, USA - [email protected] Y. Kim, The University of Texas at Austin, Austin, Texas, USA W. Walker, The University of Texas at Austin, Austin ,Texas USA

Desalination continues to grow in importance because freshwater supplies for drinking water dwindle while demand grows with increasing population. Dramatic improvements in membrane technology have made reverse osmosis (RO) systems the industry standard for desalination. Nevertheless, RO is not the universal panacea; in particular, when RO is used on inland brackish waters, the recovery (the fraction of the influent water that becomes product) is rarely higher that 80%. The other 20%, the concentrate, becomes a waste stream that is expensive and environmentally troublesome to dispose.

One possible means to improve recovery of RO desalination systems is to use electrodialysis (ED) as an interstage or post-treatment; that is, to treat the existing concentrate of an RO system using ED and thereby increase the overall recovery. The objectives of this paper are to present a simple mathematical model of ED that helps define the niche for ED in this application and to reinforce that model with laboratory experimental results.

In ED, alternating cation- and anion-exchange membranes create alternating clean (diluate) and concentrate streams. For an ion to be transported from the bulk solution in the feed stream to the bulk solution of the concentrate, it must move through five separate regions: (i) the bulk solution on the diluate side of an ion exchange membrane, (ii) a diffusion boundary layer on the diluate side of the membrane, (iii) the membrane itself, (iv) a boundary layer on the concentrate side, and (v) the bulk solution on the concentrate side. In each region, electroneutrality must be maintained, so cations and anions do not act independently of one another; slower moving ions tend to control the overall transport. The ion concentrations and potential drop adjust in various parts of the system to achieve the requirements of electroneutrality and equal electrical current (ion flux) being carried in each step at steady state. The behavior in each region is defined by the Nernst-Planck equation. Operating ED systems have a critical or limiting current, and the actual current (and consequent potential drop) must be held below this value.

In both bulk solutions and both membranes in a single-salt system, the concentrations are uniform (so diffusion is zero) and the current and potential

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drop are linearly related (although the diffusion coefficients in the membrane and solution are not the same). The boundary layers are more complex, because both electromigration and diffusion are operative. An analytical mathematical model describing the relationships among concentration (profile), current density, and potential gradient in the boundary layers for an ideal one-dimensional system at steady state has been developed and solved, and this model illustrates all of the important characteristics and limitations of real ED systems. The model has been solved for both a single salt (one cation and one anion) and two salt (one cation and two anions, or vice versa) situations; more complex mixtures require numerical solutions which are under development at the time of writing. To our knowledge, such a model has not previously been presented.

The analytical model elucidates the influence of several factors on ED design and operation more directly than more complex numerical models. For example:

(i) The concentration for the single-salt solution varies linearly with distance in the boundary layer, and the absolute value of the slope increases with increasing current and decreasing diffusion coefficient of the selected ion. (ii) The concentration decreases from either membrane to the bulk in the boundary layers of the concentrate, and decreases from the bulk to the membrane in the boundary layers of the diluate. (ii) The potential drop is expressed by a logarithmic function with distance in the boundary layer, but the relevant variables have similar functionality as in the concentration expressions. (iv) ED is most efficient when the total dissolved solids (TDS) concentration of the influent is much less than that of seawater and when the effluent TDS can be sufficiently high to allow current passage; these conditions exactly fit brackish water RO concentrate as a feedstock to create drinking water.

Along with development of the model, laboratory scale experiments are being performed using a five cell-pair electrodialyzer from PCCell, GmbH (Heusweiler, Germany). A computerized drive controls the flow rate, while a direct current regulated power supply controls the applied potential (or current). Conductivity and pH of the treatment streams are monitored continuously. A digital balance is used in flow rate calibrations and osmosis quantification. A graphical user interface and data acquisition system round out the system. A wide range of experiments have been and will be performed, and a selection of results that test and demonstrate the utility of the model will be presented.

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Desalination II – 5

Thursday July 17, 4:30 PM-5:00 PM, Honolulu/Kahuku

A Novel Three-Stage Treatment for Brackish Water Reverse Osmosis Concentrate: Parameter Effects on and Feasibility of Antiscalant Oxidation

L. Greenlee (Speaker), The University of Texas at Austin, Austin, Texas, USA - [email protected] D. Lawler, The University of Texas at Austin, Austin, Texas, USA B. Freeman, The University of Texas at Austin, Austin, Texas, USA B. Marrot, Université Paul Cézanne, France P. Moulin, Université Paul Cézanne, France

In many locations, fresh water resources are insufficient for local needs, and alternative sources with lesser water quality are being considered as drinking water supplies. In particular, the United States has many inland regions with untapped brackish water (500-10,000 mg/L total dissolved solids) resources. Reverse osmosis (RO) membrane desalination is a feasible solution, but the product recovery (volume of product water per volume of feed water) range is only 75-90%; i.e., at least 10% of the feed water becomes the RO waste stream, or concentrate. The costs and technical feasibility of concentrate disposal severely limit the application of inland RO. This research was designed to reduce the volume of brackish water RO concentrate.

In brackish water RO systems, recovery is limited by salt precipitation. Chemicals called antiscalants are used to complex with problematic salts (CaCO3, CaSO4, BaSO4, SrSO4, silica), delaying precipitation. However, salt concentration increases with recovery, and eventually precipitation control is overcome. To increase system recovery and decrease the concentrate volume, a new approach is required.

Previous research using precipitation and separation to treat concentrate has shown that significant increases in total system recovery are possible. However, the presence and influence of antiscalants and natural organic matter (NOM) during RO concentrate treatment have not been investigated.

This paper presents the development of a novel three-stage process to treat the concentrate from a brackish water RO system. The process achieves problematic salt removal through (I) antiscalant deactivation, (II) precipitation, and (III) solid/liquid separation. Antiscalant deactivation is performed using ozone (O3) and hydrogen peroxide (H2O2). pH elevation is used to precipitate salts, and solid/liquid separation is achieved through sedimentation and filtration. While technologies for solid/liquid separation are well-established, the combination of antiscalant oxidation and precipitation represents a new system; research on

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antiscalant oxidation has been limited, and the effect of ozonation on precipitation has not been investigated.

The effects of several parameters, including pH, ozonation time, water composition, antiscalant concentration and type, ozone dose (mg O3 per mg dissolved organic carbon (DOC)), and [H2O2]/[O3] ratio (mole:mole), on phosphonate antiscalant oxidation were evaluated. Increases in ozonation time, pH, and ozone dose increased antiscalant oxidation. An increase in ozonation time from 1 to 30 minutes increased fractional phosphate oxidation from 0.10 to 0.57 (pH 6), while a pH increase from 5 to 8 increased carbon oxidation from 36 to 86% (15 min ozone). Doubling the ozone dose increased oxidation by 40-90% (1-10 min ozone). The addition of H2O2 ([H2O2]/[O3] = 0.2), for the same ozone dose and pH, increased carbon oxidation by 25%. The effect of changing the [H2O2]/[O3] ratio varied, depending on the water composition; however, the ratio of 0.8 resulted in the most antiscalant degradation. Increasing the ratio from 0.2 to 0.8 increased fractional carbon oxidation by 33-250%. Changes in water composition showed the scavenging effect of the carbonate system on antiscalant oxidation; the addition of carbonate (pH 6, ozone dose = 2.6 mg O3/mg DOC and [H2O2]/ [O3] = 0.8) increased complete carbon oxidation from 47 to 58%. The extent of oxidation was different for the two antiscalants tested; differences in chemical structure affect oxidation.

The effect of oxidation on the precipitation and separation stages was then studied. Parameters having a potential effect on the precipitation stage (ozonation time, water composition, antiscalant type and concentration) were varied. In all experiments, ozonation prior to precipitation allowed greater calcium precipitation. Results showed phosphate produced during antiscalant oxidation completely precipitated during the second stage. Tests with a simplified water (containing only NaHCO3 and CaCl2) showed 97% calcium precipitation after 10 minutes ozonation, while antiscalant-dosed, non- ozonated samples showed 92% calcium precipitation. Similar results for calcium were obtained for a more complex (but synthetic) water; calcium precipitation increased from 81 to 87% with the addition of ozonation prior to precipitation. This calcium precipitation increase would increase the achievable overall recovery, due to a greater reduction in precipitation potential. A preliminary cost analysis showed a concentrate disposal cost reduction of up to 90%. The research is ongoing, and results from a natural brackish water will be presented to show the influence of NOM.

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Desalination II – 6

Thursday July 17, 5:00 PM-5:30 PM, Honolulu/Kahuku

Sustainable Seawater Desalination: Small Scale Windmill and RO-System

S. Heijman (Speaker), Delft University of Technology, Delft, The Netherlands - [email protected] E. Rabinovitch, Delft University of Technology, Delft, The Netherlands J. van Dijk, Delft University of Technology, Delft, The Netherlands

INTRODUCTION

In coastal areas with a shortage of fresh drinking water, but enough wind power, the combination wind energy and reverse osmosis may provide a sustainable way to produce drinking water. Especially in remote areas and with high water prices the combination is cost effective. At the moment there are windmills providing electricity for RO installations. But in these systems the wind energy is first transferred to electricity and than transferred back to mechanical energy for the high pressure pump. Often the electricity is also stored in order to overcome periods of low wind speeds. The system is rather expensive because of the energy loss and the storage of electricity. It is of course less expensive to store the fresh water and drive the high pressure pump directly with wind energy.

OBJECTIVE

A commercial windmill, normally used for irrigation purposes, is converted with a gearbox and a shaft running down to ground level. The windmill is driving a high pressure piston pump. The piston pump is connected directly to the mill shaft with the right rotation speed for the pump. An energy recovery system uses the energy from the concentrate. The energy recovery is also securing a fixed (water) recovery of 30% at different wind speed. The installation will produce between 5 and 10 m3 of fresh water a day. It produces only water if there is enough wind energy, so a fresh water storage is very important. The installation will also have a mechanical dry-run protection and both a low speed and a high speed limitation.

RESULTS

The first prototype is ready in December 2007. It will be tested on salt water near Delft University and shipped to Curacao in February 2008. The results will include production of permeate as a function of the wind speed, fouling problems as a function of the wind speed and biofouling. Of course the water price is estimated by calculating the investment costs and estimating the yearly production.

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Membrane and Surface Modification II – 1 – Keynote

Thursday July 17, 2:15 PM-3:00 PM, O’ahu/Waialua

Macroporous Membrane Adsorbers with Tailored Affinity and High Capacity via Photo-initiated Grafting-of Functional Polymer Layers

M. Ulbricht (Speaker), Universität Duisburg-Essen, Essen, Germany - [email protected] D. He, Universität Duisburg-Essen, Essen, Germany J. Wang, Universität Duisburg-Essen, Essen, Germany Q. Yang, Universität Duisburg-Essen, Essen, Germany A. Yusof, Universität Duisburg-Essen, Essen, Germany

Separations with membrane adsorbers are a very attractive and rapidly growing field of application for functional macroporous membranes [1]. The key advantages in comparison with conventional porous adsorbers result from the pore structure of the membrane which allows a directional convective flow through the majority of the pores; thus, the characteristic distances for pore diffusion will be drastically reduced. The separation of substances is based on their reversible binding on the functionalized pore walls; the most frequently used interactions are ion-exchange and various types of affinity binding. However, there is still a large interest in improvement of performance for established materials and in development of novel materials. Specific aims are membrane adsorbers with higher dynamic binding capacity and membrane adsorbers with higher affinity and selectivity for certain target substances, especially via affinity binding to robust chemical ligand architectures.

Via different surface-selective photo-grafting methods developed in our group [2], various types of anion- and cation-exchange membrane adsorbers with three-dimensional binding layers had been prepared on different macroporous support membranes, from regenerated cellulose with pore diameters (dp) of 0.45, 1 and 3~5 µm, from polypropylene with dp ~0.4 µm, or for model studies track-etched poly(ethylene terephthalate) with dp of ~0.4 or ~0.8 µm. Functional monomers for weak cation-exchange and strong anion- exchange membranes, respectively, were acrylic acid [3] and 2-(methacryloyloxy)ethyl)- trimethylammonium chloride [4], respectively. Copolymerization with hydrophilic diluent acrylamide monomers was used to adjust the density of functional groups, and cross-linking with bisacrylamides was used as another parameter for tailoring the grafted architectures. The synergist immobilization method for photo-grafting [2,4] had turned out to be especially versatile because the highest surface selectivity for photo-grafting could be achieved. Dynamic evaluation of the membrane adsorbers had been done by analysis of breakthrough curves for proteins of different size and by separation of proteins based on their different isoelectric points. In all cases, a well- defined chemical cross-linking of the grafted layer via addition of a cross-linker monomer during photo-grafting lead to a markedly

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improved separation performance because higher permeability and lower susceptibilities of permeability to salt concentration than with linear grafted polymer had been combined with high dynamic protein binding capacities, i.e. the trade- off between high binding capacity and low permeability observed for linear grafted polymer chains could be partially avoided.

Finally, we will report about two novel routes to protein-selective membrane adsorbers where affinity binding occurs via multiple-site molecular recognition in grafted functional copolymer layers. Recognition is either based on the incorporation of monomers with receptor groups for specific amino acids (e.g. arginine) on the protein surface [5] or on monomers with glycosidic groups for the specific binding of a special group of proteins, the lectins [6].

[1] M. Ulbricht, Polymer 2006, 47, 2217-2262.

[2] D. M. He, H. Susanto, M. Ulbricht, �Photo- irradiation for preparation, modification and stimulation of polymeric membranes� (Invited Review), Progr. Polym. Sci., 2007, submitted.

[3] A. H. M. Yusof, M. Ulbricht, J. Membr. Sci. 2008, 311, 294-305.

[4] D. M. He, M. Ulbricht, J. Membr. Sci. 2008, accepted.

[5] D. M. He, S. Wei, T. Schrader, M. Ulbricht, to be submitted.

[6] Q. Yang, A. Friebe, Z. K. Xu, M. Ulbricht, to be submitted.

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Membrane and Surface Modification II – 2

Thursday July 17, 3:00 PM-3:30 PM, O’ahu/Waialua

Surface Modification of Pervaporation Membrane by UV-Radiation and Application of Shear Stress

P. Izák (Speaker), Institute of Chemical Process Fundamentals, Prague, Czech Republic - [email protected] H. Godinho, Universidade Nova de Lisboa, Portugal P. Brogueira, Instituto Superior Técnico, Portugal L. Figueirinhas, Instituto Superior Técnico, Portugal J. Crespo, Universidade Nova de Lisboa, Portugal

At present, one of the main challenges in green chemistry is the selective recovery of solutes from ionic liquids by clean membrane processing. Serious problems are caused by concentration polarization, in particular during pervaporation process, especially when green solvents with high viscosity (such as ionic liquids) are used. Therefore we looked for ways to promote external mass transfer in the binary mixture and thus minimize the concentration polarization at the membrane surface. The surface modification of the polyurethane (PU) and polybutadiene-diol (PBDO) membrane obtained by UV-radiation and application of shear stress allowed us to increase external mixing of the liquid feed at the membrane surface. The formed microstructures increased the enrichment factor and also permeation flux of solute. Additionally, when we increased feed flow rate in pervaporation module we also improved the pervaporation characteristics. This work demonstrates the potential of surface modified dense membranes to enhance the pervaporation separation processes.

Acknowledgements

This research was supported by the post-doc grant (SFRH/BPD/9470/2002) and the projects grants (POCTI/EQU/35437/2000 and POCTI/CTM/56382/2004) from Fundação para a Ciência e a Tecnologia, Portugal, and to the Czech Science Foundation for grant No. 104/08/0600.

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Membrane and Surface Modification II – 3

Thursday July 17, 3:30 PM-4:00 PM, O’ahu/Waialua

Microstructured Hollow Fiber Membranes for Ultrafiltration

P. Culfaz, University of Twente, The Netherlands J. Jani, University of Twente, The Netherlands R. Lammertink, University of Twente, The Netherlands - [email protected] M. Wessling (Speaker), University of Twente, The Netherlands

Hollow fibers are used in many membrane processes from gas separation to microfiltration. The fibers are most commonly made by the solution spinning method and have a round shape. Through the use of silicon micromachining technology, the spinnerets used for spinning hollow fibers can be modified to produce microstructured fibers with convolutions on the outside [1]. This is done by placing a silicon insert with a structured opening in the middle inside the spinneret, such that the polymer solution flows through this structured annulus instead of a circular annulus.

The increased surface area of the fibers is expected to result in increased flow per fiber length if the selective layer is of comparable thickness. Convoluted membranes are also suggested to cause turbulence around the convolutions, which may decrease fouling and facilitate cleaning of the membranes [2].

In this study, ultrafiltration fibers of a PES-PVP blend were made using a dry-wet spinning process. The fibers were made using a structured insert as well as a round insert for comparison. The clean water fluxes were measured to compare the throughput of the fibers. The molecular weight cut- offs were measured by filtering a mixture of dextranes. The pore size distribution and skin layer thickness will also be examined to have a complete comparison of the structured and the round fibers made under identical conditions. The fouling behavior of the fibers was evaluated in modules of ca. 140 cm2 membrane area (5-7 fibers) by filtering a 50 ppm humic acid solution. Fluxes from 20 - 100 L/h.m2 were used. The transmembrane pressure difference required to obtain the set flux was measured and from this the membrane resistance was calculated.

First, structured fibers were made applying increasing air gaps between the spinneret outlet and the coagulation bath. Using a solution of 20% PES, 5% PVP K30, 5% PVP K90, 5% H2O and 65% NMP, the complete loss of the structure in the fiber occurred within 60 mm of an air gap. When a 6 mm air gap was used, the structured fiber had 80% higher surface area compared to the round fiber made under the same conditions. For equal length of fiber subjected to the same transmembrane pressure difference, the structured fiber had 90% higher flowrate. The molecular weight cut-offs of the round and structured fibers were

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both 15±5 kDa, which suggests that the pore sizes of the round and structured fibers are similar.

Using finite element methods, the evolution of the initial convoluted shape towards a round shape could be simulated. The shape evolution is controlled by the solution viscosity and surface tension. The outcome of the simulation fits the actual behavior of the fiber quite well. Using these simulations new inserts which can retain the structure longer in the air gap can be designed.

In the fouling tests, it was observed that the structured fibers showed no irreversible fouling after the filtration of the humic acid solution, whereas the round fibers did. The structured fibers used in these experiments had 55% higher surface area than their round equivalents and the flowrate through these structured fibers was 40% higher than the round fibers.

Using a modified spinneret to make structured hollow fibers appears to be a promising method to enhance the throughput and reduce the fouling of ultrafiltration membranes. While keeping the separation characteristics the same, the throughput can be increased and fouling can be reduced.

References:

[1] Nijdam, W., De Jong, J., Van Rijn, C.J.M., Visser, T., Versteeg, L., Kapantaidakis, G., Koops, G.-H., Wessling, M., 2005, Journal of Membrane Science 283, p. 209-215.

[2] Scott, K., Mahmood, A.J., Jachuck, R.J., Hu, B., 2000, Journal of Membrane Science 173, p. 1-16.

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Membrane and Surface Modification II – 4

Thursday July 17, 4:00 PM-4:30 PM, O’ahu/Waialua

High Performance Surface Nano-Structured RO/NF Membranes

G. Lewis, University of California, Los Angeles, California, USA N. Lin (Speaker), University of California, Los Angeles, California, USA M. Kim, University of California, Los Angeles, California, USA Y. Cohen, University of California, Los Angeles, California, USA - [email protected]

Reverse Osmosis (RO) and Nanofiltration (NF) membranes used for surface and groundwater desalination are susceptible to bio-organic fouling (i.e., proteins, humic acid, fulvic acid), colloidal fouling and mineral salt scaling. Membrane fouling and/or scaling not only results in a decreased membrane permeate flux but also protein adhesion and mineral salt scale formation that may permanently alter the physical features of the surface and lead to irreparable membrane damage. Previous strategies for mitigating membrane fouling/scaling (i.e., polymer surface adsorption and UV, gamma irradiation, and low-pressure plasma graft polymerization) have relied on alteration of the membrane surface chemistry and topography by addition of a permselective polymer thin film that would act both as a separation layer and a physical boundary to prevent adsorption of organic and mineral salt species. In the present study, a novel atmospheric pressure plasma-induced graft polymerization method was developed to enable the generation of a high surface density of active surface sites for subsequent graft polymerization using a suitable monomer. Surface graft polymerization was then carried out to form a dense layer of grafted polymer chains that are covalently and terminally bound to the surface. The chemical and physical features of the resulting grafted polymer film may be tuned by altering the monomer chemistry as well as the reaction conditions to achieve unique architectures for effective advanced materials in membrane separations.

Using the above approach of atmospheric pressure plasma-induced graft polymerization (APPIGP), a novel class of RO and NF membranes were developed. Characterization of membrane bio-organic fouling studies were conducted in a dilute aqueous feed stream of model proteins. Surface scaling was evaluated by subjecting the surface structured membranes to a dilute aqueous mineral salt solution with the onset of mineral scaling detected by a novel scale-observation imaging system. The properties of the grafted polymer on the RO and NF membranes, specifically the surface density, polymer chain length, and monomer chemistry, were evaluated with respect to the membrane performance (i.e., onset of mineral scaling, water permeate flux decline and surface scale coverage) to determine the optimal surface structuring conditions required reduce surface fouling/scaling. The properties of the grafted surfaces, such as surface topology and surface feature uniformity, were evaluated by

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Atomic Force Microscopy (AFM), and the surface chemistry was elucidated by Fourier Transform Infrared (FTIR) Spectroscopy. The results suggest that surface modification of both RO and NF membranes by plasma-induced graft polymerization can be an effective tool for increasing membrane performance by decreasing the propensity for scaling and fouling.

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Membrane and Surface Modification II – 5

Thursday July 17, 4:30 PM-5:00 PM, O’ahu/Waialua

Characterization of Commercial Reverse Osmosis Membrane Performance and Surface Modification to Enhance Membrane Fouling Resistance

E. Van Wagner (Speaker), The University of Texas at Austin, Austin, Texas, USA B. Freeman, The University of Texas at Austin, Austin, Texas, USA – [email protected] M. Sharma, The University of Texas at Austin, Austin, Texas, USA

Thin-film composite reverse osmosis (RO) membranes have been studied for nearly fifty years, gradually evolving to the high water flux, high salt rejection (typically >98%) materials used today. However, the high throughput and selectivity that make RO membranes viable candidates for desalination also make measuring their properties difficult. Additionally, commercial RO membranes are prone to fouling by contaminants present in potential alternative water sources, making membrane surface modification a current area of significant interest. This study was undertaken to identify some important variables responsible for measured performance values (water flux and salt rejection) of commercial RO membranes, and also to modify the commercial membrane surfaces to make more fouling-resistant materials.

First, polyamide RO membranes obtained from Dow FilmTec (XLE and LE) were characterized using carefully controlled testing conditions mimicking those of the manufacturer. The measured water flux and salt rejection values were in good agreement with the benchmarks. In addition, the effects of feed pH and continuous feed prefiltration on membrane flux and rejection were studied. Concentration polarization was accounted for in all experiments.

Surface modification of the well-characterized commercial RO membranes was then performed. Short-chain molecules based on poly(ethylene glycol) diglycidyl ethers or fluoroalkyl oxiranes were used to form chemical bonds between their epoxide endgroups and free amines present on the RO membrane surface. Variables including reaction method (dip or spin coating), time, temperature, and molecular weight and concentration of grafting molecule were studied for their effect on flux and rejection. The fouling resistance (i.e., flux decline) of modified and unmodified membranes was compared in model foulant solutions.

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Membrane and Surface Modification II – 6

Thursday July 17, 5:00 PM-5:30 PM, O’ahu/Waialua

Hydrophobic Modified Ceramic Membranes for Gas Separation and Desalination

S. Cerneaux (Speaker), Institut Européen des Membranes, Montpellier, France - [email protected] S. Condom, Institut Européen des Membranes, Montpellier, France M. Persin, Institut Européen des Membranes, Montpellier, France E. Prouzet, Institut Européen des Membranes, Montpellier, France A. Larbot, Institut Européen des Membranes, Montpellier, France

Ceramic membranes are hydrophilic by nature since hydroxyl groups are present both on the surface and within inner pores of membranes. Hence, this characteristic is highly suitable to perform membranes surface modification to confer them a specific affinity depending on the targeted applications. For water treatment and desalination, attention has been focused on membranes showing a hydrophobic feature as it yields to the formation of a repellent barrier for liquid water transfer in Membrane Distillation (MD) processes, which are driven by a temperature difference across hydrophobic membranes and only allow water vapor permeation. In gas separation, these hydrophobic membranes are also of great interest as perfluorinated chains used in this work are well known to have a specific affinity for the CO2 gas molecules.

To post-functionalize zirconia, alumina and titania ceramic materials with different pore diameters, perfluoroalkyl alkoxysilane molecules CnF2n+1(CH2)2Si(OR)3 were used. Materials were chemically modified by reaction of the different fluorinated alkoxysilanes in alcoholic media for 4h and efficiency of grafting was evaluated by FTIR, TGA and solid-state 29Si NMR for corresponding modified powders. The influence of the perfluorinated chain length on the hydrophobic stage of the modified membranes was further evidenced by measuring the water liquid entry pressure and the wettability, water contact angles higher than 140° being obtained for n=6 and n=8. The pore diameters of the modified membranes need to be considered in desalination and liquid separations as they represent the limiting factor for rejection rate and flux in desalination. Modified zirconia membrane with pore diameters of 50nm yielded to the highest flux and rejection rates higher than 99%, while working in Direct Contact Membrane Distillation. Preliminary results in CO2 separation using hydrophobic zirconia membranes showed that a pure gas selectivity of 3 for CO2 against N2 can be achieved with a CO2 permeance of 0.2 m3(STP)/m2.h.bar.

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Hybrid Membranes – 1 – Keynote

Thursday July 17, 2:15 PM-3:00 PM, Wai’anae

Polymer-Zeolite 4A Mixed-Matrix Nanocomposite Gas Separation Membranes

A. Kertik, Istanbul Technical University, Istanbul, Turkey I. Agil, Istanbul Technical University, Istanbul, Turkey C. Atalay-Oral, Istanbul Technical University, Istanbul, Turkey S. Tantekin-Ersolmaz (Speaker), Istanbul Technical University, Istanbul, Turkey - [email protected]

Polymer/zeolite mixed matrix composite (MMC) membranes are hybrid materials offering the potential to overcome the permeability-selectivity trade-off limitation of polymeric membranes. These hybrid membranes combine high selectivity of zeolites and easy processability of polymers when proper polymer/zeolite pair is selected and good adhesion is achieved at the polymer/zeolite interphase. However, experimental studies in the literature have shown that when good adhesion is ensured, permeability values decrease pointing out an interfacial region around the zeolite particles showing more resistance to gas flow than the polymeric matrix which is often described as chain rigidification around the zeolite particle. The interphase effect in MMC membranes was investigated in our earlier studies and a model (Modified Effective Medium Theory (EMT)) was developed to include the interphase resistance [1,2].

Presence of an interphase surrounding zeolite particles contributing to the effective permeability is especially important from an industrial perspective since commercial application of membranes require asymmetric membrane configuration with thin (<1 micron) selective layers, and the use of zeolites with small particle size. Advances in nanotechnology for the synthesis of well-defined nanoscaled zeolites with high reproducibility enables the preparation of ultra thin polymer-zeolite MMC membranes for obtaining high product rates; however, the use of zeolites with smaller particle size results in enhanced area and number of zeolite-polymer interfaces, and hence may cause considerable reductions in effective permeabilities.

This work focuses on the development of polymer/zeolite MMC membranes for O2/N2 and CO2/CH4 separation applications. Zeolite 4A was chosen as the model dispersed phase. Polyetherimide (Ultem) and polyvinyl acetate (PVAc) were chosen as the polymeric matrices. Zeolite particles were treated by a priming protocol [3] before incorporation into the polymeric matrix to enhance good adhesion at the polymer/zeolite interphase. MMC membranes are characterized to investigate their separation characteristics and the polymer/zeolite interphase. Gas separation characteristics of unfilled and filled membranes were investigated

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by single gas permeation experiments. The interfacial effect of zeolite particle size on MMC membrane separation characteristics is investigated by comparing the properties of membranes prepared with nanosize zeolites with an average particle size of 200 nm and commercial zeolites with 2-5 microns particle size. The experimental permeability data obtained in this study were also compared with the effective permeability predictions of EMT and Modified EMT models. The results indicated differences in the magnitude of chain rigidification between different polymer-zeolite systems. The differences in the characteristics of the polymeric phase change the behavior and the severity of the interphase characteristics.

References

[1] Tantekin-Ersolmaz, S. B., Atalay-Oral, C., Tatlier, M., Schoeman, B., Sterte, J. (2000) Effect of Zeolite Particle Size on the Performance of Polymer-Zeolite Mixed Matrix Membranes, J. Memb. Sci.. 175:285-288.

[2] Erdem-Senatalar, A., Tatlier, M., Tantekin-Ersolmaz, S. B. (2001) Estimation of the Interphase Thickness and Permeability in Polymer-Zeolite Mixed Matrix Membranes, Stud. Surf. Sci. Cat. 35:154.

[3] Mahajan, R. and Koros, W. J. (2000) Factors Controlling Successful Formation of Mixed-Matrix Gas Separation Materials, Ind. Eng. Chem. Res. 39:2692-2696.

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Hybrid Membranes – 2

Thursday July 17, 3:00 PM-3:30 PM, Wai’anae

Hollow Fillers For Flux Enhancement In Mixed Matrix Membranes

K. Vanherck (Speaker), Katholieke Universiteit Leuven, Heverlee, Belgium S. Aldea, Katholieke Universiteit Leuven, Heverlee, Belgium A. Aerts, Katholieke Universiteit Leuven, Heverlee, Belgium J. Martens, Universiteit Leuven, Heverlee, Belgium I. Vankelecom, Katholieke Universiteit Leuven, Heverlee, Belgium - [email protected]

Mixed matrix membranes (MMMs), consisting of an organic polymer (bulk phase) and inorganic particle phases (dispersed phase), have the potential to combine high selectivities with high membrane fluxes. Zeolites and carbon molecular sieves have been most attractive as inorganic fillers in MMMs because their very defined pore structure increases the selectivity. Zeolite-filled polydimethylsiloxane (PDMS) membranes have already been developed for gas separation, pervaporation, and nanofiltration. PDMS is known to be a chemically and thermally stable polymer, but the excessive swelling and resulting selectivity loss in certain organic solvents (e.g. toluene, DCM,&) limits its utility in these solvents. The incorporation of zeolites reduces PDMS swelling via extra cross-linking, without lowering the intrinsic fluxes. In previous research, composite membranes were prepared with a PDMS top layer filled with zeolites ZSM-5 and USY. Top layer thicknesses of approximately 8µm could be obtained, giving a 92% rejection for Wilkinson Catalyst in toluene at a permeability of 1,07 l/m² bar h. Since a zeolite-filled PDMS top layer requires a certain minimal thickness to remain free of defects, it is not easy to obtain higher fluxes.

To lower the minimal thickness of a zeolite-filled PDMS toplayer, two strategies were explored in this research. Firstly, zeolites with a smaller crystal size, nano-sized silicalite-1 (NS), were used as fillers. Secondly, the incorporation in PDMS of micron-sized hollow spheres (HS) with a zeolite shell was investigated. Hollow spheres with a shell consisting of nano-sized silicalite crystals and a diameter of <1 to 5 micron were self-synthesized. The synthesis involved adding a solution of cetyl trimethylammonium bromide in ethanol dropwise to a clear solution whilst stirring and placing the resulting solution in an oven until a white precipitate was formed. The precipitate was then buchner filtrated, repeatedly washed with ethanol and calcined.

The top layer thickness of PDMS filled with NS could be lowered to 3-5 micron, but performance in toluene and DCM was unsatisfactory. The calcination of the NS particles prior to using them as a filler caused condensation of the silanol groups on the surface of these particles which resulted in a strong particle aggregation, observed via SEM. This resulted in a bad zeolite dispersion. The

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PDMS toplayers were only partially cross-linked by the zeolites, explaining the strong swelling and rejection loss in toluene and DCM. For the MMMs with a toplayer of PDMS filled with HS, a high increase in permeability was expected since the hollow fillers should allow a fast flow of the solvent. At the same time, rejection should be maintained by the molecular sieving and cross-linking effect of the silicalite-1 shell of the HS. The toplayer thickness that could be obtained varied between 10 and 20 micron. The MMMs showed an increased flux (normalized to a top layer thickness of 3 micron) in nanofiltration experiments with isopropanol and Bengal rose (2,13 l/m² bar h) compared to the zeolite filled PDMS (0,12- 0,67 l/m² bar h) and unfilled PDMS (0,25 l/m² bar h) without loss of rejection (99%). In DCM and toluene, preliminary results were disappointing due to a problematic adhesion between the PDMS toplayer and the polyimide support. The improvement of this adhesion is still under study.

The described method should not be limited to hollow substances with zeolitic shell nor to PDMS as a polymer. Any type of hollow compound with a shell composed of inorganic material functional for the preparation of MMMs can be used to improve permeabilities. It is expected that the described method will improve fluxes not only in the nanofiltration field but also for pervaporation and gas separation.

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Hybrid Membranes – 3

Thursday July 17, 3:30 PM-4:00 PM, Wai’anae

Elaboration and Characterization of a Hybrid Membrane Based on Hydrophilic Polymer/Ceramic Membrane for Metal Affinity Chromatography

M. Dubois, Institut Européen des Membranes, Montpellier, France C. Muvdi Nova, Institut Européen des Membranes, Montpellier, France D. Paolucci-Jeanjean (Speaker), Institut Européen des Membranes, Montpellier, France - [email protected] M. Belleville, Institut Européen des Membranes, Montpellier, France M. Rivallin, Institut Européen des Membranes, Montpellier, France M. Barboiu, Institut Européen des Membranes, Montpellier, France P. Bacchin, Laboratoire de Génie Chimique, Toulouse, France

Membrane chromatography was introduced as an integrative technology for the purification of proteins several years ago. In general, the membrane process could offer some advantages such as no intraparticle diffusion, short axial- diffusion path, low pressure drop, no bed compaction, easier scale up, which are usually limited in the conventional packed-column chromatographic systems [1]. Consequently, membrane chromatography is a promising large- scale separation process for the isolation, purification, and recovery of proteins [2].

Almost all publications on membrane chromatography systems deal with organic membranes which offer a large choice of functional chemical groups for ligand grafting. In this study, an original hybrid membrane was chosen : a ceramic support brings the mechanical and chemical strength required for industrial applications whereas an organic layer brings the functional chemical groups involved in the ligand grafting.

The elaboration of the hybrid metal affinity chromatography membrane involves 4 steps : i) coating of a polymer layer in order to functionalize the ceramic support, ii) cross-linking and activation of the polymer layer, iii) grafting of a metal chelating agent, iv) metal ion adsorption.

First, ceramic supports are functionalized by coating hydrophilic polymers on or inside the membrane by tangential filtration of diluted chitosan or polyvinyl alcohol (PVA) aqueous solutions in order to provide amine or hydroxyl groups able to fix active compounds.

Then, functionalized membranes are cross-linked and activated with bisoxiranes such as epichlorohydrin or 1,4-butanediol diglycidyl ether. On the one hand, this step enables to stabilize the polymer layer (by cross-linking) and on the other hand it provides epoxy groups for the metal- chelating-agent grafting. It is worth

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noting that cross-linking agents constitute spacer arms which increase the ligand accessibility and facilitate protein retention.

In the next step, iminodiacetic acid (IDA), a metal- chelating agent, is attached to the epoxidized membranes.

Finally, Cu2+ is chelated by IDA-grafted membranes during dead-end filtration of a CuSO4 aqueous solution.

Different membranes are elaborated and the influence of several parameters (polymer nature, cross-linking conditions, IDA grafting conditions) on Cu2+ adsorption and thus protein retention is checked.

Cu2+ adsorption capacities are estimated at 290 mg.m-2 for the chitosan-membrane and 160 mg.m-2 for the PVA-membrane. These results are in the same order of magnitude than those obtained for other organic membranes [3-5]. The PVA-membrane adsorbs a lower quantity of Cu2+ than the chitosan-membrane but as the adsorption is more specific, it remains attractive.

The hybrid affinity membranes obtained are then used for bovine serum albumin and lysozyme retention.

Acknowledgement The authors acknowledge the French ANR (Agence Nationale pour la Recherche) for the financial support of the PROMEMGEL project (ANR-05-JC05- 47316)

References

(1)E.Klein, Affinity membranes : a 10 years review, J Memb.Sci., 179, 2000, 1.

(2)C.Charcosset, Purification of proteins by membrane chromatography, J. Chem. Techn. Biotech., 71, 1998, 95.

(3)T.C. Beeskow and W. Kusharyoto, Surface modification of microporous polyamide membranes with hydroxyethyl cellulose and their application as affinity membranes, J. Chromatogr. A, 715, 1995, 49.

(4)Y.H. Tsai, M.Y. Wang and S.Y. Suen, Purification of hepatocyte growth factor using polyvinyldiene fluoride-based immobilized metal affinity membranes: equilibrium adsorption study, J. Chromatogr. B., 766, 2002, 133.

(5)C.Y. Wu, S.Y. Suen, S.C. Chen and J.H. Tzeng, Analysis of protein adsorption on regenerated cellulose-based immobilized copper ion affinity membranes. J. Chromatogr. A., 996, 2003, 53.

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Hybrid Membranes – 4

Thursday July 17, 4:00 PM-4:30 PM, Wai’anae

Optimization of SRNF Membranes Cast from Emulsified Polyimide Solutions: Comparison of a Traditional Approach with a High Throughput/Combinatorial Approach

P. Vandezande (Speaker), Katholieke Universiteit Leuven, Leuve, Belgium - L. Gevers, Flemish Institute for Technological Research (VITO), Mol, Belgium N. Weyens, Department of Chemistry-Biology-Geology, Diepenbeek, Belgium I. Vankelecom, Katholieke Universiteit Leuven, Leuven, Belgium - [email protected]

Solidification of Emulsified Polymer Solutions via Phase Inversion (SEPPI) has recently been presented as a novel approach to create porous polymeric structures with controlled porosity [1]. SEPPI involves the preparation of an emulsified polymer solution through the addition of an organic suspension containing nano-sized silicalite-1 particles [2]. This polymeric emulsion is subsequently solidified by simple contact with a polymer non-solvent, with the droplets acting as template for the final pores. A wide variety of polymers could thus be turned into porous materials with tunable pore characteristics via a number of easily accessible parameters at the level of the emulsion. Thanks to the nano- dimensions of the particles and the insertion of an evaporation step prior to solidification of the cast films, highly selective polyimide (PI) membranes with thin top- layers could be prepared, which were successfully applied in solvent resistant nanofiltration (SRNF) [3].

Being a membrane process able to separate organic mixtures down to a molecular level at pressures between 5 and 20 bar, SRNF has a huge potential in treating non-aqueous streams, mainly found in the food, petrochemical, fine-chemical and pharmaceutical industries [3]. SRNF membranes are typically applied to retain organic compounds with MWs ranging from 200 to 1000 g/mol. Environmental and economical concerns explain the steadily increasing interest in SRNF as a sustainable technique to treat solvent streams. In view of the expected growth of the SRNF market, a clear need still exists to develop more and better membranes to solve separation problems in existing industrial processes and open new application areas.

As many parameters are involved in membrane synthesis, for instance via phase inversion, testing and optimization of membranes has always been time-consuming. Using a traditional parameter- by-parameter approach, in which all possible parameters are systematically, but independently screened, the development of a new membrane with optimal properties would be extremely slow, but also ineffective since it is very improbable to find the overall optimum of

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such extended parameter space in this way. An important challenge in developing and optimizing membranes is thus to find and implement more efficient search strategies, which rapidly focus on the most promising spots within the parameter space, thus increasing the chance on finding the membrane with the best separation of the targeted compounds. The feasibility of high throughput (HT) techniques and combinatorial search strategies in membrane research has been demonstrated earlier with the successful optimization of PI based asymmetric SRNF membranes in a 8- dimensional compositional parameter space [4].

Similar to the latter study, asymmetric, nanozeolite-filled membranes, prepared from emulsified PI solutions via the SEPPI method, were optimized here for their performance in the separation of the low molecular weight dye rose Bengal (1017 g/mol) from IPA. All membranes were prepared and tested in a parallellized, miniaturized and automated manner using laboratory- developed HT experimentation techniques [4,5]. Only parameters related to the composition of the casting solutions were investigated; all other synthesis conditions were kept constant. Membranes were ranked according to their objective function, a fitness- proportional numerical figure based on both permeance and retention values, relative to predefined target and threshold performances. First, a preliminary systematic screening was carried out, in which four constituents were used, i.e. Matrimid® PI, NMP as solvent, THF as volatile co-solvent and NMP-based nanozeolite sol as emulsifying agent. After, a combinatorial strategy, based on a genetic algorithm and a self-adaptive evolutionary strategy, was applied to optimize the membrane performance in an extended, 9- dimensional parameter space, comprising two extra solvents (DMSO and DMAc), the two corresponding nanozeolite suspensions, and another co-solvent (1,4-dioxane). Coupling with HT techniques allowed to prepare three generations of casting solutions (176 compositions), resulting in 125 membranes. With IPA permeances up to 3.3 l.m-

2.h-1.bar-1 and RB rejections around 98%, the combinatorially optimized membranes scored significantly better than the best membranes obtained in the systematic screening. The most performant SEPPI membranes also showed much higher IPA permeances than the commercial MPF- 50 and Starmem" 120 membranes, at similar or slightly lower RB rejections. Moreover, the organomineral SEPPI membranes proved to be more compaction-resistant.

References

[1] P. Vandezande et al., accept. for public. in Chem. Mater.

[2] R. Ravishankar et al., J. Phys. Chem. B 1999, 103, 4960.

[3] P. Vandezande et al., Chem. Soc. Rev., 2008, 37, 365.

[4] M. Bulut et al., J. Comb Chem. 2006, 8, 168.

[5] P. Vandezande et al., J. Membr. Sci. 2005, 250, 305.

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Hybrid Membranes – 5

Thursday July 17, 4:30 PM-5:00 PM, Wai’anae

Crosslinking and Stabilization of MgO Filled PTMSP Nanocomposite Membranes for Gas Separation

L. Shao (Speaker), Norwegian University of Sci. and Tech., Trondheim, Norway M. Hägg, Norwegian University of Sci. and Tech., Trondheim, Norway - [email protected]

Poly(1-trimethysilyl-1-propyne)[PTMSP] is a stiff chain, high free volume glassy polymer known for its very high gas permeability, but consequently then also relatively low selectivity. The high gas permeability could be an advantage, but is unstable over time. It has been reported that the oxygen permeability of PTMSP decreased by 1 order of magnitude during storage at 25 °C for 30 days under vacuum. The gas permeability in this polymer is also sensitive to processing history. PTMSP undergoes significant physical aging which is caused by the gradual relaxation of non-equilibrium excess free volume in glassy polymers. Additionally, organic solvents may degrade PTMSP, and hence all these disadvantages may compromise the practical use of this high permeation polymer.

The current study investigates the effect of crosslinking PTMSP on transport properties and physical aging. PTMSP has been crosslinked using bis azides to improve its chemical and physical stability. Crosslinking PTMSP renders it insoluble in good solvents for the uncrosslinked polymer. Gas permeability and fractional free volume (FFV) decreased as crosslinker content increased, while gas sorption was unaffected by crosslinking. Therefore, the reduction in permeability upon crosslinking PTMSP was due to decreases in diffusion coefficients. Compared to the pure PTMSP membrane, the permeability of the crosslinked membrane is initially reduced for all gases tested due to the crosslinking. By adding nanoparticles MgO, the permeability is again increased; permeability reductions due to crosslinking could be offset by adding nanoparticles to the membranes. Increased selectivity is documented for the gas pairs O2/N2, CO2/N2, CO2/CH4 and H2/CH4 using crosslinking and addition of nanoparticles. Crosslinking is successful in maintaining the permeability and selectivity of PTMSP membranes and PTMSP/filler nanocomposites over time.

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Hybrid Membranes – 6

Thursday July 17, 5:00 PM-5:30 PM, Wai’anae

Preparation High Performance Microporous/Mesoporous Hybrid Membranes for Gas Separation

Q. Liu (Speaker), Dalian University of Technology, Dalian, China X. Zhao, Dalian University of Technology, Dalian, China T. Wang, Dalian University of Technology, Dalian, China - [email protected] S. Liu, Dalian University of Technology, Dalian, China Y. Cao, Dalian Institute of Chemical Physics, Dalian, China J. Qiu, Dalian University of Technology, Dalian, China

Carbon molecular sieving (CMS) membrane is considered to be one of the most promising inorganic membrane materials for membrane-based gas separation because of their excellent selectivity and thermal and chemical stability even under harsh conditions, such as high pressure and high temperature. However, the separation performance of this material still can not satisfy the practical application requirement owing to their low permeability.

Herein, a novel carbon-based microporous/mesoporous hybrid membrane has been successfully designed and prepared for gas separation. The as-synthesized hybrid material is composed of continuous microporous carbon matrix and dispersed mesoporous material SBA-15. It is well known that gas transport through ordered mesoporous materials is governed by the Knudsen diffusion mechanism with negligible contribution from viscous flow. Therefore, the gas diffusion rate in the mesoporous materials is several orders of magnitude faster than that in microporous materials. The incorporation of mesoporous material SBA-15 will help to increase the gas diffusion rate in the membranes and improve the gas separation performance.

The characterization results conducted by XRD, TEM and nitrogen sorption analysis indicated that the mesoporous material SBA-15 was well dispersed in the carbon matrix and the mesoporous structure of SBA-15existed in hybrid membrane was not destroyed during pyrolysis. The gas permeation tests using small molecules (H2, CO2, O2, N2 and CH4) showed that the hybrid membrane exhibited outstanding permeability together with high selectivity, which indicated that gas transport through the hybrid membranes was still controlled by the molecular sieving effect. The correlation of the permeability versus the selectivity for the hybrid membrane showed higher values than the Robeson upper bounds for polymeric membranes. And the gas separation performance of the membranes were also higher than the polyimide-derived carbon membranes. The excellent gas separation performance for all tested gases makes the microporous/mesoporous hybrid membrane an attractive material in gas separation areas.

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Oral Presentation Abstracts

Morning Session

Friday, July 18, 2008

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Plenary Lecture III

Friday July 18. 8:00 AM-9:00 AM, Hawai’I Ballroom

The Development of Reverse Osmosis and Nanofiltration through Modern Times

William E. Mickols (Speaker), DOW Water Solutions, Edina, Minnesota - [email protected]

The history of reverse osmosis (RO) began with the discovery of osmotic pressure. Modern thermodynamics offered the explanation of how theoretical chemical activity differences could be used to develop a physical pressure difference. Further developments in stochastic theory showed how either a physical pressure or a chemical concentration difference could be expressions of the same effect. The actual proof of using pressure to develop a chemical gradient was left to Loeb and Sourirajan. Their work on cellulose based symmetric and asymmetric RO membranes amazed the scientific and popular world. This mobilized the scientific world to convert their discovery from a scientific curiosity to a viable method to desalinate water.

The development of RO was driven, in part, by considerations that 80% of the world’s surface is covered with water too saline to drink. Recently we have found that 60-80% of the remaining water is too contaminated to drink by World Health Organization (WHO) standards. Of the remaining 20-30% drinkable water, much of it is becoming contaminated and will require extensive remediation.

Modified celluloses were initially used to make asymmetric RO membranes. Charged thermoplastics were also extensively studied. Modern RO membranes began with asymmetric aromatic polyamides in the hollow fiber form. The recent explosion in RO began with the development of interfacial synthesis of thin film composites by John Cadotte at North Star research. Initial development used polyimine based cross-linked polyamides (NS200). This began the parade of remarkable high flux, high rejection reverse osmosis membranes.

With the development of interfacial synthesis of two new aromatic polyamides, the concept of nanofiltration and RO was developed. The FilmTec NF-40 membrane (piperazine and TMC) and FT-30 (meta phenylene diamine and TMC) launched the modern industry. Over the course of 20 years the water permeability increased by a factor of eight and the salt permeability dropped by almost a factor of twenty. Separations that required 400 psi now only require 50 psi and have better rejection. Modification of the surface of FT-30 has also allowed RO to operate at very low ionic strengths. The altered charged surfaces changed the ion rejection characteristics at low ionic strength. For high ionic strength we’ve shown that by designing the membrane to fit the separation, the efficiency of RO separations can be increased by a factor of over 50%. Modern

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alteration of the structure of FT-30 includes designs for specific solute rejections. This includes cutting the passage of neutral solutes like boric acid by 40%. Contamination of water supplies with neutral solutes and difficult to remove solutes has fueled recent advances in RO chemistry. General methods to reduce solute passage are being developed across the globe. Continuing to redesign RO membranes will allow us to improve the passage of other important solutes which will drive further utilization of RO throughout the world.

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Gas Separation V – 1 – Keynote

Friday July 18. 9:30 AM-10:15 AM, Kaua’i

Designing Membranes for Future Membrane Gas Separation Applications

R. Baker (Speaker), Membrane Technology and Research, Inc., Menlo Park, California, USA - [email protected]

Using membranes for gas separation is now big business. Close to $500 million of equipment is sold each year, 50,000-100,000 plants for separation of nitrogen from air have been installed, and natural gas plants with membrane areas of several hundred thousand square meters have been built. In this talk, the current technical status of the gas separation membrane industry will be described. This will be followed by a discussion of some membrane separations under development: water from bioethanol, carbon dioxide from coal power plant flue gas, and olefins from paraffins. The relationships between process design and the type of membrane needed will be addressed.

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Gas Separation V – 2

Friday July 18, 10:15 AM-10:45 AM, Kaua’i

Sorption and Dilation of Crosslinked Poly(ethylene oxide) Membranes by Carbon Dioxide and Ethane

C. Ribeiro (Speaker), The University of Texas at Austin, Austin, Texas, USA B. Freeman, The University of Texas at Austin, Austin, Texas, USA - [email protected]

Carbon dioxide constitutes a common impurity that must be removed from natural gas to improve its heating value. For low gas flow rates, membrane units have already been installed to perform this separation instead of the traditional process based on absorption in amine solutions. However, due to plasticization by carbon dioxide and higher hydrocarbons, the selectivity and flux of current commercial membranes, based on cellulose acetate and polyimides, are not high enough to compete with amine systems for medium and large gas flow rates. Therefore, new membrane materials for this separation are sought.

Crosslinked poly(ethylene oxide)-based (XLPEO) membranes have been recently identified as a promising alternative for the selective removal of carbon dioxide from light gas mixtures. Copolymers synthesized by photopolymerization of different composition ratios of poly(ethylene glycol) diacrylate (PEGDA) and poly(ethylene glycol) methyl ether acrylate (PEGMEA) exhibited excellent separation performance for CO2/hydrocarbon mixtures in permeation experiments carried out with both pure gases and gas mixtures [1, 2]. Contrary to cellulose acetate and polyimides, XLPEO-based membranes are solubility selective and, therefore, the determination of their sorption characteristics for different gases is of considerable importance. Even though pure gas sorption data for these materials are already available [3], these were all obtained neglecting the effect of polymer dilation, which can be rather significant.

In the present contribution, pure gas dilation and sorption data for two different XLPEO-based materials with carbon dioxide and ethane are reported at temperatures ranging from -20 to 35oC. The importance of taking polymer dilation into account to determine the gas solubility in the polymer was clearly demonstrated. In particular, the PEGMEA content, previously believed to have a negligible effect on gas sorption [4], was shown to influence gas solubility significantly. The amount of carbon dioxide sorbed in the polymer for a given gas activity increased with decreasing temperature, whereas, in the case of ethane, the opposite trend was observed. For each temperature, sorption and dilation data were combined to calculate the respective partial molar volume of each gas in the polymer and the results were compared with available literature data for other rubbery polymers.

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References:

[1] H. Lin, E. Van Wagner, R. Raharjo, B. D. Freeman, I Roman. High-performance polymer membranes for natural-gas sweetening. Advanced Materials, 18, 39-44, 2006.

[2] S. Kelman, H. Lin, E. S. Sanders, B. D. Freeman. CO2/C2H6 separation using solubility selective membranes. Journal of Membrane Science, 305, 57-68, 2007.

[3] H. Lin and B. D. Freeman. Gas and vapor solubility in cross-linked poly(ethylene glycol diacrylate). Macromolecules, 38, 8394-8407, 2005.

[4] H. Lin, E. Van Wagner, J. S. Swinnea, B. D. Freeman, S. J. Pas, A. J. Hill, S. Kalakkunnath, D. S. Kalika. Transport and structural characteristics of crosslinked poly(ethylene oxide) rubbers. Journal of Membrane Science, 276, 145-161, 2006.

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Gas Separation V – 3

Friday July 18, 10:45 AM-11:15 AM, Kaua’i

Kinetic Sorption and Permeation Behavior of Water Vapor in Polymeric Membranes

H. Sybesma, University of Twente, The Netherlands J. Potreck, University of Twente, The Netherlands K. Nymeijer (Speaker), University of Twente, The Netherlands - [email protected] R. van Marwijk, KEMA, The Netherlands R. Heijboer, KEMA, The Netherlands M. Wessling, University of Twente, The Netherlands

Objective

Coal-fired power plants produce electricity and in addition to that large volume flows of flue gas, which mainly contains N2, O2, CO2 and water vapor, but also pollutants such as nitric oxides (NOx), sulfur dioxide (SO2), and fly ash. As a consequence of gas cleaning steps, the temperature of the flue gas decreases and the gas stream becomes saturated with water vapor. This can easily lead to condensation of water vapor in the stack of the power plant, which causes corrosion. To prevent condensation, traditionally reheating of the flue gas is required, resulting in extra energy consumption and additional costs.

Membrane technology is an attractive technology to remove part of the water vapor to prevent condensation. The application of membranes for this separation is especially attractive due to the possibility of re-use of the water and the additional energy savings.

In the present work we present such a membrane system with extremely high separation factors and fluxes for the removal of water vapor from flue gasses. The work combines fundamental understanding of the kinetic sorption and transport behavior of water vapor in macromolecular structures with more applied knowledge to show the potential of the developed membranes for industrial flue gas dehydration [1-3].

Kinetic sorption analysis

An economically viable membrane process for the dehydration of flue gasses requires membranes with extremely high water vapor fluxes combined with a very low non-condensable flux. Several materials were investigated and the results clearly show the superior performance of sulfonated poly(ether ether ketone) (SPEEK), especially at higher water vapor activities. Sorption isotherms of water vapour in this glassy polymer were determined experimentally and the

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relative contributions of Fickian diffusion and relaxational phenomena are quantified as a function of the water concentration in the polymer using the Hopfenberg-Berens model. The hydrophilic nature of the polymeric material, especially for higher degrees of sulfonation, results in very high water vapour sorption values, high swelling and subsequently high Fickian diffusion coefficients. The results proof the occurrence of both Fickian sorption behaviour and relaxation phenomena already at very low water concentrations in the polymer matrix. With increasing water concentration, the glass transition temperature of the swollen polymer decreases and the relative importance of relaxation phenomena increases whereas that of Fickian diffusion decreases.

Mixed gas and water vapor permeation behavior

Composite hollow fiber membranes with a dense top layer of SPEEK were developed and characterized in terms of their mixed water vapor/nitrogen permeability and selectivity. Membrane modules were prepared and used for a 150 h experiment with artificial flue gas. 0.6 to 1 kg/m2 hr of water with a conductivity of 2 µS/cm was removed continuously and no visible changes in membrane structure or morphology were observed.

The developed membranes were used for flue gas dehydration in long-term exposure tests under real flue gas conditions in a 450 MW coal fired power plant. The prepared membranes were placed directly into the aggressive flue gas stream and the performance was monitored. To create a driving force for permeation, the overcapacity of the condenser system already present in the power plant could be used. An average water vapor removal rate of 0.2 to 0.46 l/m2 h was obtained during a continuous period of 5300 hours.

Finally, the experimental data were used as input values for computer simulations to identify the influence of the process parameters on the installed membrane area. Simulations stress the importance of very high water vapor permeabilities combined with very low inert gas fluxes for an economically viable process.

Conclusions

In the present work we present a gas separation membrane with extremely high separation factors and fluxes for the removal of water vapor from flue gasses. The work combines fundamental understanding of the kinetic sorption and transport behavior of water vapor in macromolecular structures with more applied knowledge to show the potential of the developed membranes for industrial flue gas dehydration.

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References:

1. Hylke Sijbesma, Kitty Nymeijer, Rob van Marwijk, Rob Heijboer, Jens Potreck, Matthias Wessling, Flue gas dehydration using polymer membranes, J. Membrane Sci. (2007), doi:10.1016/j.memsci.2008.01.024.

2. J. Potreck, F. Uyar, H. Sijbesma, K. Nymeijer, D. Stamatialis, M. Wessling, Kinetic sorption behavior of water vapor in sulfonated poly ether ether ketone, In preparation.

3. J. Potreck, T. Kosinski, K. Nymeijer, M. Wessling, Sorption, diffusion and transport phenomena of water vapor in PEBAX®, In preparation.

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Gas Separation V – 4

Friday July 18, 11:15 AM-11:45 AM, Kaua’i

Natural Gas Purification Using High Performance Crosslinked Hollow Fiber Membranes: Effects of High Pressure CO2 and Toluene Feed.

I. Omole (Speaker), Georgia Institute of Technology, Atlanta, Georgia, USA S. Miller, Chevron Energy Technology Company, Richmond, California, USA W. Koros, Georgia Institute of Technology, Atlanta, Georgia, USA - [email protected]

Natural gas is one of the fastest growing primary energy sources in the world today. The increasing world demand for energy requires increased production of high quality natural gas. For the natural gas to be fed into the mainline gas transportation system, it must meet the pipe-line quality standards. Natural gas produced at the wellhead is usually ‘sub-quality’ and contains various impurities such as CO2, H2S, and higher hydrocarbons, which must be removed to meet specifications.

Carbon dioxide is usually the largest impurity in natural gas feeds and high CO2 partial pressures in the feed can lead to plasticization, which causes loss of some methane product and may ultimately render the membrane ineffective. Moreover, the presence of highly sorbing higher hydrocarbons in the feed can further reduce membrane performance.

Covalent crosslinking has been shown to increase plasticization resistance in dense films by suppressing the degree of swelling and segmental chain mobility in the polymer, thereby preserving the selectivity of the membrane. This research focuses on extending the dense film success to asymmetric hollow fibers.

In this paper, the effect of high pressure CO2 (up to 400 psig CO2 partial pressure) on CO2/CH4 mixed gas separation performance was investigated on the hollow fiber membrane at different degrees of crosslinking. All the crosslinked fibers were shown to exhibit good resistance to selectivity losses from CO2 induced plasticization, significantly more than the uncrosslinked fibers. Robust resistance of the hollow fiber membranes in the presence of toluene (a highly sorbing contaminant) was also demonstrated as the membranes showed no plasticization even in toluene saturated feed streams.

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Gas Separation V – 5

Friday July 18, 11:45 AM-12:15 PM, Kaua’i

Synthesis and Gas Permeability of Hyperbranched Polyimide Membranes

K. Nagai (Speaker), Meiji University, Kawasaki, Japan - [email protected]

The mobility of polymer chains is larger for their polymer terminal chain ends as compared to that for their polymer main chains. Therefore, gas-induced plasticization may occur easily around the polymer chain ends as compared to around the polymer main chains. Moreover, if the number of polymer chain ends is minimized in a membrane, gas-induced plasticization would be prevented. In order to reduce the number of polymer chain ends as well as their mobility, hyperbranched polymer membranes were prepared, and the plasticization resistance of their carbon dioxide (CO2) permeability was investigated. The base polymers for hyperbranch were the polyimides based on 4,4'- (hexafluoroisopropylidene)diphthalic anhydride (6FDA). The diamine used for these polyimides was either 3,4-diaminodiphenyl ether (3,4DADE) or 2,3,5,6-tetramethyl-1,4-phenylene diamine (TeMPD). Both chain ends of the linear 6FDA- based polymer were capped with either 4-(2- phenylethynyl)phthalic anhydride (PEPA) or p- aminostyrene. For example, in the case of 6FDA- 3,4DADE-PEPA, the hyperbranch structure was formed by the cycrotrimerization of three acetylene groups in three PEPA groups in the presence of tantalum chloride (V), which act as a catalyst. The linear base polyimide was soluble in chloroform and so on, while the hyperbranched one showed poor solubility in the same solvents. In addition, the hyperbranched polyimides had larger membrane density than their base linear counterparts. During CO2 exposure at 40 atm and at 35C, the CO2 permeability coefficient in the base linear polyimide membranes increased with time, whereas in the hyperbranched one, the polyimide membranes were stable, indicating resistance for CO2 plasticization.

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Gas Separation V – 6

Friday July 18, 12:15 PM-12:45 PM, Kaua’i

The Effect of Water on the Gas Separation Performance of Polymeric Membranes for Carbon Dioxide Capture.

C. Scholes, CRC for Greenhouse Gas Technologies, Victoria, Australia R. Hasan, CRC for Greenhouse Gas Technologies, Victoria, Australia S. Kentish (Speaker), CRC for Greenhouse Gas Technologies, Victoria, Australia - [email protected] G. Stevens, CRC for Greenhouse Gas Technologies, Victoria, Australia

Polymeric gas separation membranes for natural gas, pre- and post-combustion carbon dioxide capture must contend with water, which generally saturates the feed gas. The presence of water competes with carbon dioxide in sorption into the Langmuir volume of the polymeric membrane. This competitive sorption generally results in decreased carbon dioxide permeability in the membrane compared to dry gas, and therefore a loss in performance. Furthermore, the presence of water can act as a plasticizer, and over time alter the polymeric structure leading to time dependent ageing of the membrane, and possibly failure. Here, the impact of water on a range of glassy polymeric membranes are studied; polysulfone, Matrimid and 4,4-(hexafluoroisopropylidene) diphthalic anhydride (6FDA-Durene), as well as the rubbery material poly dimethylsiloxane (PDMS). The purpose of this work is to model the water affected carbon dioxide separation performance under conditions that mimic real carbon capture systems. Results will be compared to upcoming plant trials to be conducted under the Energy Technology Innovation Strategy (ETIS) program for both pre- and post- combustion carbon dioxide capture.

For all polymeric membranes, glassy and rubbery, a loss in carbon dioxide permeability occurs upon exposure to wet feed gas, indicative of competition from water. This behaviour is modelled for glassy membranes as competitive sorption in the dual- sorption model; and used to evaluate the affinity of water for the Langmuir volume within the membranes. Exposure over longer timescales (hours) result in improved carbon dioxide permeability for both poly sulfone and 6FDA- Durene. This is a consequence of plasticization of the membranes by water, altering the glassy polymeric matrix to a more rubbery state. This behaviour is not observed for Matrimid, and is associated with the difference in free volume of the polymeric membranes, and therefore their susceptibility to plasticization.

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Nanofiltration and Reverse Osmosis III - Applications – 1 – Keynote

Friday July 18, 9:30 AM-10:15 AM, Maui

Fundamental Study and Performance Advancement of Seawater RO Membrane

M. Henmi (Speaker), Toray Industries, Inc., Shiga, Japan - [email protected] H. Tomioka, Toray Industries, Inc., Shiga, Japan T. Kawakami, Toray Industries, Inc., Shiga, Japan M. Kurihara, Toray Industries, Inc., Shiga, Japan

In seawater reverse osmosis (SWRO) desalination field, boron removal is a significant matter to be conquered since it is known to show male reproductive tract per oral administration in laboratory animals. WHO has established the boron concentration in drinking water to be below 0.5mg/L as a guideline value. Boron exists as boric acid in seawater, and its concentration is 4 to 7 mg/L. Boric acid is the typical substance which is difficult to be removed by RO membrane since it is a very small molecule having about 0.4 nm in diameter. Although conventional RO membrane elements have shown a little more than 90% of boron rejection, it was still inadequate and necessary to use some supportive processes to remove boron. Accordingly, high boron rejection membrane is desirable for reducing the loading to such supportive processes. We have recently been investigating SW RO membranes with focusing on high boron removal, and its performance is getting better every year. The boron rejection rates of the recent membranes have been improved up to 94 - 95 %, and fundamental researches into the substance removal mechanism of RO membrane have been carried out for the achievement of further excellent performance.

Spectroscopic structure analyses for various RO membranes, which were selected from those of having an aromatic polyamide separating functional layer and different performance upon boron removal, but equal salt removal, were performed to obtain the molecular structure information and the parameters influencing to substance removal. Positron annihilation lifetime spectroscopy (PALS) study with positron beam method nondestructively provided the information of the pore sizes in the range of 5.6 - 7.0 angstroms for several SWRO membranes as against of 50 - 70 angstroms for an NF membrane. Consequently, the correlation between the measured pore size and the boron removal performance in RO membranes was also revealed. Solid-state 13C NMR spectroscopy demonstrated all the peaks of each chemical functional group in separating functional layer of the RO membranes and the presumptive molecular structures of the polyamide were estimated. Molecular dynamics analyses based on the estimated molecular models were performed, and the calculated pore sizes were well agreed with the measured ones. Transmission

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Electron Microscopy (TEM) analyses of protuberance of RO membrane surface shows the probability of membrane potential improvement. Through these studies, special molecular design, which controls the pore size in RO membrane, is needed to the development of further renovate membrane. In this presentation, the prospect of attaining a new renovative high boron rejection membrane will be discussed.

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Nanofiltration and Reverse Osmosis III - Applications – 2

Friday July 18, 10:15 AM-10:45 AM, Maui

Development and Testing of a High-Capacity, Mobile Desalination System

M. Miller (Speaker), U.S. Army TARDEC, Port Hueneme, California, USA - [email protected] M. Chapman, Bureau of Reclamation, Denver, Colorado, USA C. Barley, NSF International, Ann Arbor, Michigan, USA M. Blumenstein, NSF International, Ann Arbor, Michigan, USA B. Shalewitz, U.S. Army TARDEC, Port Hueneme, California, USA

In late 2002 a multidisciplinary team of U.S. military and government personnel were enjoined in response to a congressional initiative to stimulate discovery and invention in science and technology pertaining to water purification, and verify as well as validate the utility of emerging state of the art science and technology in water purification systems. The EUWP program was established to address two principal objectives. The first was to fund research in the academic and commercial sectors to further the state of desalination technology, while the second was to develop a mobile, high-capacity desalination system intended to showcase technological innovations that may have application for future military water purification equipment. This presentation will address the development and evaluation of the EUWP technology demonstrator.

The objective of the EUWP demonstrator is to develop a system that maximizes production, yet achieves transportability requirements important to the military. The primary design constraint for the equipment is that it be air transportable. Achieving air transportability requires that the overall system weight and size be minimized. This resulted in the incorporation of several technologies not used in military water purification systems at the time, as well as a change in design philosophy. Some examples include:

- Ultrafiltration with coagulant addition: Due to the mobile nature of the system and feed water conditions that are expected to be encountered, the EUWP utilizes ultrafiltration (UF) to be able to treat high turbidity water with minimal footprint. In an effort to further reduce system size and weight, coagulant addition is employed resulting in the ability to operate the UF system at higher flux rates for extended periods of time. An additional benefit of UF is that the high quality water provided can enable operating the reverse osmosis (RO) system at higher flux and recovery rates. - Energy recovery: The incorporation of energy recovery allows the system to produce more water with no additional power burden. In addition, the size of the high-pressure pump and motor can be reduced resulting in overall space and weight savings.

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- Hybrid RO train: A hybrid RO train consisting of three different RO elements is employed to provide a more balanced flux distribution between elements and an increased production over a conventional RO train. Using a hybrid RO train results in the need for fewer RO membranes and therefore a smaller package.

Pilot testing of the UF and RO systems was conducted prior to their incorporation into the system design. These tests confirmed important performance parameters and operational constraints prior to incorporation into the system. Final evaluation of the system based on the EPA’s Environmental Technology Verification (ETV) program was pursued in 2006 and 2007 due to the potential employment of the system for use in disaster relief missions. ETV evaluations were conducted on three different water sources to evaluate performance of the entire system as well as several of the subsystems. Feed waters included seawater, surface water and a secondary effluent with high biological content to challenge the prefiltration system. The primary objective of the ETV testing was to verify that the system meets water quality objectives; however the evaluation of performance metrics pertaining to the UF and RO systems were also included to evaluate membrane performance. ETV testing exceeded 2,000 hours.

The incorporation of the aforementioned technologies has resulted in arguably the highest production system per unit volume and weight than any stand-alone water purification system in existence. The EUWP has been successfully deployed on three separate occasions.

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Nanofiltration and Reverse Osmosis III - Applications – 3

Friday July 18, 10:45 AM-11:15 AM, Maui

Investigation of Amphoteric Polybenzimidazole (PBI) Nanofiltration Hollow Fiber Membrane for both Cation and Anion Removal

J. Lv, National University of Singapore, Singapore K. Yu Wang (Presenting), National University of Singapore, Singapore T.-S. Chung, National University of Singapore, Singapore - [email protected]

High levels of harmful ions in the surface and ground waters have become a major health problem in many countries. Harmful anions removal can be achieved by adsorption, precipitation and electrocoagulation, ion exchange and extraction. Membrane separation processes have been proven to be a feasible and promising option for the removal of toxic ion species. Using nanofiltration (NF) membranes to remove toxic species of wastewater has also been carried out. Generally, positively-charged NF membranes are only effective for cations removal, whereas negatively- charged NF membranes are only effective for anions removal. In this study, the removal of both anions (phosphate, arsenate, arsenite and borate ions) and cations (copper ions) has been investigated by employing a lab-developed amphoteric polybenzimidazole (PBI) nanofiltration (NF) hollow fiber membrane. The amphoteric characteristics are due to the imidazole group within PBI molecules that makes the PBI NF membrane having an isoelectric point near pH 7.0 and shows different charge signs based on the media pH. Investigations on the rejection capability of typical anions, e.g. phosphate, arsenate, arsenite, borate anions and typical heavy metal cations, e.g. copper ions, reveal that the PBI NF membrane exhibits impressive rejection performance for various ion removals. However, their rejections are strongly dependent on the chemical nature of electrolytes, solution pH and the feed concentrations. The experimental results are analyzed by using the Speigler-Kedem model with the transport parameters of the reflection coefficient and the solute permeability (P) with the aid of molecular model and ion sizes. The PBI NF membrane may have potential to be used in industrial removal of various environmentally- unfriendly ion species.

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Nanofiltration and Reverse Osmosis III - Applications – 4

Friday July 18, 11:15 AM-11:45 AM, Maui

Nanofiltration of Ferric and Ferrous Cations in Acidic Solutions

X. Bernat (Speaker), ETSEQ, Universitat Rovira i Virgili, Terragona, Spain F. Stüber, ETSEQ, Universitat Rovira i Virgili, Terragona, Spain A. Fortuny, Universitat Politècnica de Catalunya, Barcelona, Spain C. Bengoa, Universitat Rovira i Virgili, Terragona, Spain A. Fabregat, ETSEQ, Universitat Rovira i Virgili, Terragona, Spain J. Font, ETSEQ, Universitat Rovira i Virgili, Terragona, Spain - [email protected]

Ferric and ferrous ions are used as catalyst in advanced oxidation processes, in conjunction with hydrogen peroxide, to accelerate oxidation reactions for partially mineralizing organic biorefractory substances. Fenton process, Fe/H2O2, is the most popular technique based in this principle. As a result, homogeneous iron leaves the oxidation step with the treated wastewater posing potential environmental and economical problems. Nanofiltration is being studied and applied as a promising technology to recover multivalent ions and organic compounds from aqueous polluted streams achieving additionally partial softening of these waters. Several mechanisms such as charge repulsion between the membrane and the targeted compound and sieving are involved in the mechanisms allowing the retention of the targeted ions or compounds. In addition, several operating variables may affect the efficiency of the separation process by lowering the permeate fluxes during the operation. The transmembrane pressure, the pH, the hydrodynamic conditions, the presence of other species and still others may influence the retention, the permeate rate and the fouling during the filtration process. In this work, the recovery of ferrous and ferric ions from aqueous solution by nanofiltration is presented. The experiments were conducted in a commercial batch stirred filtration cell. The effect of several operating variables on both the iron retention and the permeate flux were studied. NF, NF90 and NF270 membranes (manufactured by Dow Filmtec) were selected for this work as they are commercially available membranes that possess different isoelectric points and charge densities on their surfaces. The solutions to be treated were adjusted at pH 2, which is typical pH for effluents treated by Fenton process. The effect of the transmembrane pressure, the stirring speed, the presence of NaCl and the iron concentration on the iron retention and permeate flux decline is illustrated. The results show that low permeate flux decline was achieved and high Fe (III) retention (up to 99.9%) was obtained with all the tested membranes, assuring the final quality of the permeate and the possibility of reusing the retentate in the oxidation reactor. When comparing Fe (III) and Fe (II) performance, a lower iron charge caused a decrease of the iron retention due to the poorer charge repulsion phenomena between the charged membrane surface and the Fe (II) ions. NF90, which is a specially designed membrane for the recovery of iron, showed the highest Fe (III)

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retention but it also gives the lowest Fe (II) retention when compared to NF and NF270. In addition, NF90 membrane exhibited remarkable permeate flux decline, which make it not very attractive for this use. In turn, NF and NF270 membranes showed very similar Fe (III) and Fe (II) retentions. However, permeate flux decline of NF270 was higher than that of NF. As NF270 permeability is much higher than that of NF, NF270 is considered the best option for the effective recovery of ferrous and ferric ions from acidic solutions by nanofiltration and will be further tested in Fenton treatment as means to confine the homogeneous reaction and recover clean water.

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Nanofiltration and Reverse Osmosis III - Applications – 5

Friday July 18, 11:45 AM-12:15 PM, Maui

Treatment of the Groundwater Contaminated by High Concentration of Arsenic

M. R. Alizadehfard (Speaker), WorleyParsons, Australia - [email protected] M. H. Alizadehfard, Curtin University, Bentley, Australia

Arsenic classified as Group 1 carcinogenic substance to humans based on powerful epidemiological evidence. Arsenic cannot be destroyed; it can only be transformed into different forms or combined with other elements to be converted into insoluble compounds. Therefore, there is a tremendous demand for developing expense efficient methods for arsenic removal from contaminated groundwater and drinking water. In this work, the removal of arsenic from contaminated groundwater by Membrane and Ligand technologies were investigated. The suspended solids in contaminated groundwater were removed by a 1 micron bag filter. Organic compounds in the contaminated groundwater were removed by adsorption onto granular activated carbon. The Arsenic in the groundwater, with the average initial concentration of 450 mg/l, was concentrated by rejecting through a thin film composite reverse osmosis (RO) membrane unit. The arsenic concentration in the final RO permeate was reduced to 2 mg/l by passing two times through the two stages RO membrane pilot unit. The arsenic concentration in RO concentrate was increased to 2500 mg/l prior to Electrochemical (Ion Exchange membrane) unit. RO permeate was captured by passing through a thin bed of zirconium hydroxide media. The arsenic concentration in the final treatment was reduced to 0.05 ppm. Then, the arsenite/arsenate mixture was removed from the media with an alkaline solution forming sodium arsenite and sodium arsenate. This solution was treated by a proprietary electrochemical process in a specially designed cell to plate the arsenic as metalloid onto a cathode.

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Nanofiltration and Reverse Osmosis III - Applications – 6

Friday July 18, 12:15 PM-12:45 PM, Maui

Purification of Glucose/Sodium Lactate Solutions By Nanofiltration: Selectivity Improvement By the Addition of a Mineral Salt

C. Umpuch, Suranaree University of Technology, Nakhon Ratchasima, Thailand S. Galier, Université de Toulouse, Toulouse, France S. Kanchanatawee, Suranaree University of Technology, Nakhon Ratchasima, Thailand H. Roux-de Balmann (Speaker), Université de Toulouse, Toulouse, France - [email protected]

Nanofiltration is expected to be adapted to the separation of neutral solutes, like sugars, from charged ones, like organic acid salts depending on their molecular weight. This is the case of glucose and sodium lactate for instance. Previous work was thus devoted to the investigation of NF to purify glucose/sodium lactate solutions. Indeed, it was considered that such solutions are representative of those that can be encountered in the frame of the purification of lactic acid fermentation broths, in which glucose would represent the residual sugar impurities remaining after the fermentation stage.

The experimental study was carried out with an NF Desal DK membrane and solutions of increasing complexity, i.e. single solutions of glucose or sodium lactate on one hand and mixed ones, containing both solutes, on the other hand. A good selectivity was expected from single solute solutions, since the retention of glucose and sodium lactate were found to be about 80 and 20% respectively. On the contrary, it was observed that the retention of glucose in mixed solution was significantly decreased from 80 to 20%. As a result, the NF selectivity was found to be very poor. Such an effect of the presence of charged species on the retention of neutral ones was reported in different situations, with organic as well as inorganic membranes and with different kind of solutes, like organic acid salts and PEG for instance.

In this work, we try to investigate to what extend the ionic composition can influence the selectivity of the glucose/sodium lactate separation by NF. Indeed, thanks to the former results, one can expect that the addition of a third charged species, like a mineral salt, affects the sugar and organic acid salt in different manner. Then, a separation could be achieved for appropriate operating conditions. An experimental study is thus reported in which the influence of the fluid composition, and specially the mineral composition, on the selectivity of the glucose/sodium lactate separation is investigated. This is done by adding different mineral salts, like NaCl (0.1-1M) and Na2SO4 (0.1- 0.5M). It shows that, in the lower flux region, the selectivity can be significantly improved by the addition of a salt. This improvement depends on the mineral salt type and

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concentration as well as on the sodium lactate concentration. From these results, it is also possible to identify the limiting phenomena governing the retention of the different solutes through the NF membrane. Finally, this can open new possibilities for the application of NF as a purification process.

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Membrane Fouling IV - RO & Desalination – 1 – Keynote

Friday July 18, 9:30 AM-10:15 AM, Moloka’i

Studies on CaSO4 and CaCO3 Scaling of Membranes in Desalination by DCMD

F. He, New Jersey Institute of Technology, Newark, New Jersey, USA J. Gilron, Zuckerberg Institute for Water Research, Beer-Sheva, Israel K. Sirkar (Speaker), New Jersey Institute of Technology, Newark, New Jersey, USA - [email protected]

Membrane distillation (MD) whether of the DCMD (direct contact membrane distillation) or VMD (vacuum membrane distillation) variety can have a role to play in desalting highly saline waters that have considerable osmotic pressures where reverse osmosis (RO) operation becomes more expensive and problematic. Using MD in this way would allow increased recovery and help reduce the problem of concentrate disposal vexing inland desalination. To realize this promise, MD must show itself to be more resistant to scaling than RO and thus not limited by it in the way that RO is.

An analysis of the scaling potential in hollow fiber membrane-based crossflow DCMD is presented in terms of the saturation index profiles throughout the hollow fiber membrane module as a function of the location in the module for the sparingly soluble salt, CaSO4 and CaCO3, individually or mixed together. Modeling shows that the highest scaling potential is to be found at the high temperature end of the module both due to the high brine temperature and concentration polarization associated with high local fluxes. Concentration effects are far more important than temperature, although concentration polarization estimated in crossflow hollow fiber DCMD units is lower than that in spiral wound modules in RO for similar flux values.

Scaling studies carried out in DCMD using CaSO4 as the scaling salt (at saturation indices for gypsum ranging between 1.13 and 1.93) indicate that even when there was significant precipitation of CaSO4, there was no effect on the membrane vapor flux or brine pressure drop. The induction period for CaSO4 nucleation decreased with increased feed brine temperature (60-90°C) and increasing level of the degree of supersaturation. We observed no flux reduction inspite of extensive scaling deposits in solution. Similar results were obtained with CaCO3 over a wide range of temperature and SI values (11 to 64). Mixed CaCO3 + CaSO4 systems behaved similarly except the scaling deposits were extensive and somewhat stickier. Scaling studies with CaSO4 on a polymeric solid hollow fiber heat exchanger did not lead to a decrease in heat transfer performance although there was a minor increase in pressure drop. Crossflow with coated fibers prevented any flux reduction or distillate contamination by

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scaling deposits in the DCMD device whereas parallel flow did not. Noncoated fibers in a DCMD device were susceptible to faster nucleation.

As is well known, antiscalants are very effective in inhibiting scaling from deposits during the reverse osmosis (RO) membrane process. The inhibition is by physical rather than chemical mechanisms and involves adsorption processes. Will the application of antiscalants help inhibit the scaling problem if any in the membrane distillation process? This question has not been answered yet. One potential source of concern is that the membrane micropores may be wetted by its organic components. Thus, experiments were first arranged to figure out whether the hydrophobic PP membrane would be wetted by antiscalant solutions at a possible working concentration. Extensive scaling experiments with the addition of antiscalant were conducted to see the effects of concentration and different kinds of antiscalant on inhibiting scaling from deposits of CaSO4 and CaCO3. The parameters of the induction period, calcium concentration and the water vapor flux were investigated.

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Membrane Fouling IV - RO & Desalination – 2

Friday July 18, 10:15 AM-10:45 AM, Moloka’i

Development of Fouling Index to Access Colloidal Fouling in Reverse Osmosis Unit for Water Reclamation

L. Sim (Speaker), UNESCO Center for Membrane Science and Tech., Sydney, Australia Y. Ye, UNESCO Center for Membrane Science and Tech., Sydney, Australia V. Chen, UNESCO UNESCO Center for Membrane Science and Tech., Sydney, Australia - [email protected] A. Fane, UNESCO Center for Membrane Science and Tech., Sydney, Australia

Reverse osmosis technology is a promising method widely used in water reclamation such as desalination of seawater and purification of domestic water. However, due to the lack of reliable method in predicting fouling potential of the RO feed water, the subsequent system suffers severe flux decline. Consequently, intense chemical cleaning or membrane replacement becomes necessary and leads to higher operating cost of a plant. Silt Density Index (SDI) and Modified Fouling Index (MFI0.45) are the current approaches to measure the fouling potential of reverse osmosis (RO) feed water. The major drawback of these methods is that both methods do not account for the small particles in the feed and the conditions of a real RO system are not well simulated, therefore, the indices failed to represent the true fouling potential of that particular feed. In response to the poor ability of both indices, a lot of efforts have been allocated in developing better fouling index, for instance Modified Fouling Index - Ultrafiltration (MFI-UF) where ultrafiltration membrane is used instead of microfiltration membrane.

In this study, a new fouling index known as Crossflow Sampler - Modified Fouling Index (CFS-MFI) was developed. This index was performed in a typical cross flow filtration module followed by a dead-end MFI measuring device. Feed solution is pumped through a crossflow cell in order to fractionate the feed hydrodynamically. Permeate collected therefore consists of foulants that are responsible for cake formation during RO filtration. Large pore size membrane, in this study, 1.2um membrane was chosen in the CFS to ensure that any foulants which come near to the crossflow membrane surface are able to permeate through and hence are incorporated in MFI measurement. It is believed that, these foulants are responsible for the fouling in the real RO system if the same solution was used. The 10kDa PES membrane was used in the dead-end MFI measuring device. In addition, in order to further simulate fouling condition in RO system, the constant flux mode of filtration is selected in this study rather than the constant pressure mode.

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Silica colloidal solution with different particle sizes was used throughout. Preliminary experimental results revealed that CFS-MFI is linearly dependent of feed concentration as well as permeate flux. In a range of experiments where 22nm mono particle size silica solution was used, CFS-MFI values appeared to be lower than MFI-UF values but only to a small extent, ranging from 200 to 500s/L2 for operating flux of 25 to 120LMH. The influence of CFS is vaguely shown in these experiments might be due to the narrow particle distribution. In order to observe the clear effect of CFS on the MFI value, the silica mixture solution of 50ppm of 22nm silica colloidal and 70nm to 100nm silica colloidal suspension was used for another set of experiments. CFS-MFI shows significant lower value than MFI-UF. Under constant flux of 52LMH, CFS-MFI was found to be 76368s/L2 whilst MFI-UF was 87878s/L2. The difference of MFI-UF and CFS-MFI can range from 500 to 12000s/L2 at permeate flux of 28 LMH, 52 LMH and 77 LMH. Results implied that the conventional method may have overestimated the fouling propensity of the RO feed solution. The effects of other operating variables such as feed composition, permeate flux and crossflow velocity were also investigated in the study.

Acknowledgements

The authors would like to thank Department of Education, Science and Training, Australia for their financial support and this study is collaborated with the European Union 6th Framework project, Membrane-Based Desalination: An Integrated Approach (MEDINA).

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Membrane Fouling IV - RO & Desalination – 3

Friday July 18, 10:45 AM-11:15 AM, Moloka’i

The Effect of Membrane Body Conductance on the Zeta Potential of Clean and Fouled Polymer Membranes

T. Luxbacher (Speaker), Anton Paar GmbH, Austria - [email protected] A. Comerton, University of Toronto, Toronto, Canada R. Andrews, University of Toronto, Toronto, Canada D. Bagley, University of Wyoming, Laramie, Wyoming, USA

The electrokinetic or zeta potential is an important property of charged solid-liquid interfaces and provides insight regarding the charging behaviour of solid surfaces and colloidal particles immersed in a dielectric. Experimental methods to determine the zeta potential include streaming potential, electrophoresis, or electroacoustic techniques. The streaming potential method has become a common tool to determine the zeta potential of macroscopic solid surfaces of granular or fibrous substances as well as flat sheets. The application of the streaming potential to the characterization of thin-film composite membranes for water treatment is widely known. Beside the characterization of the active membrane surface, the streaming potential gives information about the interaction between the membrane and ions, organics, and surfactants, which provides useful insights into the relationship between reverse osmosis (RO) and nanofiltration (NF) membrane surface properties, separation performance and membrane fouling.

Despite of the acceptance of the streaming potential method in the field of membrane surface characterization, the effect of the electrical conductivity of the membrane bulk on the charging behaviour of the membrane surface is often underestimated. The streaming potential measurement is sensitive to surface conductivity, which is likely to occur on NF and RO membranes, and allows the determination of an apparent zeta potential only. In this paper we compare the calculated zeta potential of commercial NF and RO membranes determined from streaming potential measurements to that calculated from streaming current results. The streaming current measurement is insensitive to effects like surface conductivity or membrane body conductance and reveals the complete zeta potential information. We extend the comparison of virgin membranes to NF and RO membranes fouled with different sources for drinking water. The effect of membrane fouling on the surface chemistry is monitored by the streaming current measurement whereas the ratio between the apparent zeta potential and the correct value is affected by the change in the membrane porosity.

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Membrane Fouling IV - RO & Desalination – 4

Friday July 18, 11:15 AM-11:45 AM, Moloka’i

Mechanisms of Marine Bacteria Adhesion to Seawater RO Membranes

X. Huang (Speaker), University of California Los Angeles, Los Angeles, California, USA - [email protected] E. Hoek, University of California Los Angeles, Los Angeles, California, USA

Biofouling is among the most problematic issues for seawater desalination by reverse osmosis (RO) membranes. It is particularly difficult for seawater applications because continuous chlorination of polyamide RO membranes is not possible and because algal blooms result in periodic upsets to seawater quality � bringing increased biomass and assimilable organics into the RO system. The high ionic strength of seawater virtually eliminates electrostatic double layer interactions among foulants and membranes; hence, van der Waals and short-range interactions (acid-base, roughness, steric, metal-complexation, etc.) may govern adhesion of bacteria and organic matter. Previous research in fresh and brackish water applications suggests that membrane surface chemistry and morphology govern colloidal fouling of RO membranes. Other research suggests that calcium forms complexes between carboxylic acid functionality on foulants and polyamide RO membranes - exacerbating flux decline and making the membranes difficult to clean. We hypothesize that calcium-complexation will be important for the initial rate of bacterial adhesion to seawater RO (SWRO) membranes.

Our objective in this study is to elucidate the relative importance of van der Waals interactions, acid-base interactions, surface roughness, and calcium-complexation on bacterial adhesion to SWRO membranes. We have selected a model system comprising Halomonas pacifica (GFP), a common marine bacterium, and two commercial polyamide composite seawater RO membranes. The two membranes were selected because they represent a relatively hydrophobic, rough membrane with significant carboxylic acid functionality at its interface (Hydranautics SWC3+) and a relatively hydrophilic, smooth membrane with little carboxylic acid functionality at its interface (FilmTec SWHR). The former is expected to produce higher bacterial deposition rates due to attractive acid-base interactions and its rough, carboxylic acid rich interface. The latter membrane is expected to be relatively resistant to bacterial adhesion due to repulsive acid-base interactions and its smooth non-carboxylated interface. In some experiments, bacteria are dispersed in a real seawater matrix. In other experiments, solution chemistry is systematically controlled by addition of calcium and magnesium ions to NaCl solutions at seawater ionic strengths.

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We have systematically characterized H. pacifica physicochemical properties using light scattering, particle electrophoresis, and contact angle titrations. Membranes are characterized by atomic force microscopy, contact angle titrations, and spectroscopic analyses. We employ direct microscopic observation to visually monitor (in real-time) the deposition rates of bacteria cells onto the membrane surfaces. In addition, we evaluate the strength of bacterial adhesion by simulating membrane cleaning with various rinsing agents. Direct observation experiments are designed to systematically investigate the influence of seawater chemistry on bacterial adhesion, specifically, to identify the potential role of calcium mediated bacterial adhesion. We interpret direct observation data through an interfacial force model with inputs derived from rigorous physicochemical characterization of bacteria cells and membranes.

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Membrane Fouling IV - RO & Desalination – 5

Friday July 18, 11:45 AM-12:15 PM, Moloka’i

Optical Monitoring and Real-Time Digital Image Analysis of Mineral Scale Formation on RO Membranes

M. Kim (Speaker), University of California Los Angeles, Los Angeles, California, USA R. Rallo, Universitat Rovira i Virgili, Catalunya, Spain E. Lyster, University of California Los Angeles Y. Cohen, University of California Los Angeles - [email protected]

Upgrading the water quality of inland brackish water by RO and NF memrmbane processes is often limited in recovery due to the rise in the concentration of sparingly soluble salts in the retentate stream to levels that exceed their solubility limits. As a result, such mineral salts can precipitate in the retentate stream and crystallize on the membrane surface resulting in surface scaling that reduces permeate flux and ultimately damaging the membrane itself. Early detection of membrane surface scaling and fouling is necessary for timely initiation of fouling/scale mitigation steps. Present traditional measures of process performance trends (primarily flux decline and salt passage) are used as indirect indicators of the occurrence mineral scaling and fouling. Although numerous methods of scale and fouling detection have been proposed, it is only recently that real-time early detection of the onset of scale formation has become possible. Direct visual observations and detection of mineral scale on RO/NF membranes under high pressure have been made possible with an ex-situ scale observation detector (EXSOD) along with digital image analysis. The EXSOD system is an optically transparent high-pressure flat sheet membrane cell that allows real-time digital imaging of the membrane surface under RO process conditions. The EXSOD can be operated as a stand- alone laboratory RO system or connected to an RO/NF plant such that the EXSOD receives a side- stream from a tail element of the RO/NF plant and thus enable early detection of mineral scale. In its stand-alone mode, the EXSOD system was recently redesigned to enable real- time measurements of the kinetics of surface crystallization of mineral salts and assessment of the efficiency of scale mitigation strategies. In order to utilize the above approach, efficient on-line image analysis software was developed assisted with neural networks algorithms to enhance image analysis by providing image family groups to increase the accuracy of single crystal analysis, surface area covered by scale and shape and thus crystal type identification. Using the present approach, real-time evolution of surface scaling was evaluated for RO/NF scaling by calcium sulfate and calcium carbonate. Direct information on surface nucleation by mineral salt crystals and the rate of single crystal growth was determined over a range of operating conditions and different antiscalants, generating, for the first time, direct fundamental data on the kinetics of surface mineral salt crystallization on RO/NF membranes. These

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measurements, along with a comprehensive numerical concentration polarization model, enabled evaluation of the direct relationship between the observed flux decline and the surface area covered by mineral scale.

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Membrane Fouling IV - RO & Desalination – 6

Friday July 18, 12:15 PM-12:45 PM, Moloka’i

Effect of Foulant-Foulant Interaction on the Limiting Flux for RO and NF Membranes during Organic Fouling - Model Development and AFM Adhesion Force Measurement

C. Tang (Speaker), Nanyang Technological University, Thailand - [email protected] Y. Kwon, Stanford University, Palo Alto, California, USA J. Leckie, Stanford University, Palo Alto, California, USA

A limiting flux model has been recently developed to predict the fouling behavior of reverse osmosis and nanofiltration membranes by organic macromolecules (Tang and Leckie, 2007). Several interesting results have been observed: a) there was a maximum pseudo stable flux (the limiting flux) beyond which further increase in applied pressure did not translate to a greater stable flux; b) all membrane samples attained the limiting flux under constant pressure conditions as long as their initial flux was greater than the limiting flux; c) the limiting flux did not depend on the properties of membranes; d) the limiting flux had strong dependence on the feedwater composition, such as pH, ionic strength, and divalent ion concentration. The current study investigates the dependence of limiting flux on intermolecular interaction between foulant molecules. It was observed that the limiting flux was directly proportional to the intermolecular electrostatic repulsive force and that conditions enhancing foulant-deposited-foulant repulsion resulted in greater limiting flux values. Such observations agree well with a theoretical model capturing both hydrodynamic and DLVO interactions. Adhesion force measurements by atomic force microscopy (AFM) were also performed. The limiting flux correlated well with AFM adhesion force between the model foulant and the fouled membrane surface. Finally, membrane fouling was primarily controlled by the initial-flux-over-limiting-flux ratio - a greater ratio inevitably resulted in more severe flux reduction, greater foulant accumulation, and greater density of the foulant layer.

Reference:

C. Y. Tang and J. O. Leckie, "Membrane independent limiting flux for RO and NF membranes fouled by humic acid," Environ. Sci. Technol., vol. 41, pp. 4767-4773, 2007.

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Membrane and Surface Modification III – 1 – Keynote

Friday July 18, 9:30 AM-10:15 AM, Honolulu/Kahuku

Modification of Polyethersulfone Nanofiltration Membranes

K. Boussu, Katholieke Universiteit Leuven, Heverlee, Belgium K. Schols, Katholieke Universiteit Leuven, Heverlee, Belgium B. Van der Bruggen (Speaker), Katholieke Universiteit Leuven, Heverlee, Belgium - [email protected]

The top layer of commercial polymeric nanofiltration membranes for use in aqueous applications is in most cases composed of polyamide or polyethersulfone (PES). The main advantage of using PES membranes is the very high chemical and thermal stability. However, these membranes also have a high hydrophobicity (pernicious for membrane fouling) and a wide pore distribution (pernicious for a distinct separation between two components). To minimize these inadequacies, membrane modification is a valuable option, which can be performed in two different ways: by working on the polymer used (e.g., by sulfonating, chlorinating, addition of a copolymer) or by working on the existing membrane top layer (e.g., by grafting, plasma treatment,..).

This study focuses on different modification (or more specifically hydrophilization) techniques, applied on both commercial and laboratory-made PES nanofiltration membranes. The surfaces of these membranes were hydrophilized by means of the grafting technique, which implies that hydrophilic monomers (like acrylamide or methacrylic acid) were grafted on active places on the membrane surface after a redox reaction with K2S2O8 and K2S2O3. Moreover, in case of the laboratory-made membranes, the polymer can also be hydrophilized, e.g. by sulfonating. Starting from this hydrophilic polymer, a membrane was prepared by using the DIPS technique (Diffusion Induced Phase Separation).

After modification, the membranes were characterized thoroughly for the hydrophobicity (by contact angle measurements), the roughness (by AFM), the chemical composition of the top layer (by ATR-FTIR) and the size of the pores. A cross-flow nanofiltration set-up was used to study the performance (i.e., water permeability and membrane fouling) of the modified membranes. By comparing the characterization results of the unmodified with the modified membranes, the degree of modification was checked. Moreover, for each characteristic, the behaviour was followed as a function of time, to have an idea about the modification mechanism (reversible or irreversible).

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Membrane and Surface Modification III – 2

Friday July 18, 10:15 AM-10:45 AM, Honolulu/Kahuku

Development and Characterization of Ceramic Microfiltration Membrane Devices for Biomolecule Separation

R. Malaisamy (Speaker), Howard University, Washington DC, USA - [email protected] L. Lepak, Cornell University, Ithaca, New York, USA M. Spencer, Cornell University, Ithaca, New York, USA K. Jones, Howard University, Washington DC, USA

Conventional techniques for bioseparations are frequently being replaced by membrane separation processes, owing to increased versatility and efficiency of membranes. In this study, we are tailoring the surface properties of ceramic (alumina) microfiltration membranes by spin coating thin layers of a protein, collagen, for biomolecule separation applications. Commercial anodized alumina membranes were sulfonated by heating in concentrated sulfuric acid for 15 minutes. A commercially available (US Biological) aqueous solution of 0.3% bovine dermal collagen was spin deposited on the alumina membranes. Either 3 or 6 layers of collagen were spun and crosslinked into fibrils by immersing the composite membrane in an aqueous solution of dilute glutaraldehyde for 10 minutes. The membranes were then rinsed by immersion in a series of dilute aqueous buffers, and gradually dehydrated through immersion in a series of dilutions of ethanol in preparation for critical point drying.

IR spectra were obtained for the modified dried membranes and confirmed the presence of collagen protein on the substrate. When viewed by scanning electron microscopy, the thin film composite membranes appeared to have collagen fibrils spun uniformly on the alumina surface, covering the pores of the alumina considerably. The water contact angle values for unmodified alumina and sulfonated alumina membrane surfaces were measured to be 38±2° and 34±2° respectively, whereas the contact angle increased to 78±6° when collagen was spun onto the membranes. The zeta potential (surface charge) of both pure alumina and sulfonated alumina membranes at a pH of 5.5 using 1mM KCl electrolyte solution was around 30 mV, where as it was around 20 mV for the collagen modified membranes. The pure water permeability was found to lie around 200 L/(m2.h.psi) for the sulfonated alumina base membrane, but declined to 90 and 10 L/(m2.h.psi), when it was coated with 3 and 6 layers of collagen respectively. The permeate flux value at 30 psi for sulfonated alumina was 5000 L/(m2.h), but the flux dropped by almost 50% for 3 layer coated membranes, and was only 260 L/(m2.h) with 6 spun-on layers. These permeability and flux values for the collagen coated membranes are comparable to ultrafiltration and loose nanofiltration membranes, and are expected to be suitable for biomolecule separation.

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Membrane and Surface Modification III – 3

Friday July 18, 10:45 AM-11:15 AM, Honolulu/Kahuku

Solvent Resistant Nanofiltration with Partially Hydrolyzed Asymmetric Polyacrylonitrile Membranes

P. Vandezande (Speaker), Center for Surface Chemistry and Catalysis, Katholieke Univ. Leuven, Belgium X. Li, Center for Surface Chemistry and Catalysis, Katholieke Univ. Leuven, Belgium K. Vanderschoot, Centre Center for Surface Chemistry and Catalysis, Katholieke Univ. Leuven, Belgium I. Willems, Center for Surface Chemistry and Catalysis, Katholieke Univ. Leuven, Belgium I. Vankelecom, Center for Surface Chemistry and Catalysis, Katholieke Univ. Leuven, Belgium - [email protected]

Over the last few years, new technical achievements and a growing acceptance of membrane technology in industry have increased interest in membranes to separate non-aqueous streams. Particularly solvent resistant nanofiltration (SRNF), where organic mixtures are separated on a molecular level by simply applying a pressure gradient, has experienced a significant growth, spurred by increasing environmental concerns and energy prices [1]. Offering a sustainable alternative for traditional separation techniques, SRNF holds a vast potential in a vraiety of solvent-intensive processes were low molecular weight compounds (typically 200-1000 g/mol) are to be separated from organic solvents. Such applications are mainly found in the food, fine-chemical, pharmaceutical and petrochemical industries.

In SRNF, an ideal membrane combines chemical, mechanical and thermal stability with excellent rejections and high permeabilities. Unfortunately, applications are yet difficult in certain demanding solvents such as the aprotic solvents DMF, NMP, DMAc and DMSO, since none of the polymeric SRNF membranes currently available on the market resists these solvents. Solute recovery and solvent purification in industries that commonly use these aprotic solvents therefore generally rely on conventional separation techniques such as energy-consuming distillations or waste- generating extractions. The development of SRNF membranes with a high flux and a low MWCO)in these solvents can provide a sustainable alternative for these processes.

Since most polymers dissolve in aprotic solvents, the membrane-forming polymer should be chosen so that it can be modified to be able to withstand these solvents. Integrally skinned asymmetric polyimide membranes, prepared by phase- inversion, have been chemically cross-linked with diamines to allow applications in chemically rigorous environments, i.e. aprotic solvents and THF [2,3].

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Polyacrylonitrile (PAN) UF membranes are mainly used for water treatment, but have also been applied as support for thin film composite SRNF membranes [1]. Despite their relatively good chemical stability, e.g. in hexane and toluene, PAN membranes can not be used in more aggressive solvents such as DMF, DMSO and THF. Moreover, due to the poor solubility of PAN in most solvents, it is practically not feasible by phase-inversion only to reduce the pore size of PAN membranes into the range needed for NF selectivity. Different modification techniques, such as heat treatment in the presence of ZnCl2, and low temperature plasma grafting of styrene, have been applied to transform PAN based UF membranes in (SR)NF membranes [1]. These modifications did however not imply chemical stability in aprotic solvents. Partial hydrolysis of the nitrile groups of PAN membranes under alkaline conditions is frequently applied to render the surface of the membranes hydrophilic and charged [4]. Membrane Products Kiryat Weitzman patented a procedure for the synthesis of composite SRNF membranes composed of an interfacially cross-linked top layer on top of a PAN support which is on its turn cross-linked through immersion in a base, followed by heat treatment [5]. These modified membranes clearly showed improved stability in aprotic solvents.

The synthesis of partially hydrolyzed, asymmetric, purely PAN based SRNF membranes and their use for selective separations in aprotic solvents has however never been reported. In the presented work, PAN UF membranes were prepared by casting DMSO/THF based PAN solutions and immersing the obtained films in de-ionized water. These membranes were then immersed (1-60 min) in a concentrated (1-10 wt./vol.%) aqueous base solution (NaOH or NaOCH3) at elevated temperatures (25-90°C). Hydrolysis resulted in a partial conversion of the nitrile groups into carboxyl, amidine, acrylamide and other functional groups [6], as observed via ATR-IR. This chemical change was accompanied by an average decrease of the pore diameter in such a way that selectivities in the NF range were obtained. While a minimal degree of cross-linking was required for chemical stability in aprotic solvents, the membranes completely dissolved in the base medium under more stringent hydrolysis conditions due to their increased hydrophilicity. Effective cross-linking could thus only be achieved in a relatively small stability window. Small dyes with MW ranging from 300 to 1000 Da were successfully separated from DMF, NMP, DMAc, DMSO and THF at high permeabilities. The cross-linked membranes showed moreover excellent long-term stabilities.

References

[1] P. Vandezande et al., Chem. Soc. Rev. 2008, 37, 365.

[2] K. Vanherck et al., accept. for public. in J. Membr. Sci. (2008)

[3] Y.H. See Toh et al., J. Membr. Sci. 2007, 301, 3.

[4] Z. Wang et al., J. Membr. Sci. 2007, 304, 8.

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[5] C. Linder et al., US Pat. 5 039 241 (1991) and US Pat. 5 032 282 (1991).

[6] A.D. Litmanovich et al., Macromol. Chem. Phys. 2000, 201, 2176.

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Membrane and Surface Modification III – 4

Friday July 18, 11:15 AM-11:45 AM, Honolulu/Kahuku

Hydrophilic Modification of Polypropylene Hollow Fiber Membrane

S. Kim (Speaker), Kyung Hee University, Gyeonggido, Korea - [email protected] H. Kim, Kyung Hee University, Gyeonggido, Korea J. Kim, Kyung Hee University, Gyeonggido, Korea

Polypropylene hollow fiber membrane was hydrophilized by EVOH dip coating followed by low temperature plasma treatment and UV irradiation. EVOH coating attained high water flux without any pre-wetting treatment but its stability was not guaranteed at high water permeation rate. Gradual flux decline was observed due to swelling and delamination of the EVOH coating layer, which caused pore blocking. However, plasma treatment reduced the swelling, which suppressed delamination of the EVOH coating layer from PP support, which resulted in relieving the flux decline. UV irradiation with hydrophilic monomers helped crosslinking of the EVOH coating layer to enhance the performance at low water permeation rate. FT-IR and XPS analyses revealed that EVOH dip coating performed homogeneous coating not only on membrane surface but also into the membrane matrix. Thermogram of EVOH film modified by plasma treatment and UV irradiation showed the increase of crosslinking density of EVOH layer. Chemical modification by plasma treatment and UV irradiation stabilized the hydrophilic coating layer to increase the critical flux of the membrane, when it was operated in submerged mode.

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Membrane and Surface Modification III – 5

Friday July 18, 11:45 AM-12:15 PM, Honolulu/Kahuku

Effect of Surface Modifying Macromolecules Stoichiometric Ratio on Composite Hydrophobic/Hydrophilic Membranes Characteristics and Performance in Membrane Distillation

M. Qtaishat (Speaker), University of Ottawa, Ottawa, Canada - [email protected] T. Matsuura, University of Ottawa, Ottawa, Canada M. Khayet, University Complutense Madrid, Madrid, Spain

This study aims to develop novel hydrophobic/hydrophilic composite membranes that are made specifically for membrane distillation (MD). The concept of hydrophobic/hydrophilic composite membrane for MD was firstly proposed by Khayet et al. [1,2]; where surface modifying macromolecules (SMMs) were synthesized and blended with the host polyetherimide (PEI) to prepare composite membranes. Those membranes were further tested for desalination by direct contact membrane distillation (DCMD). The SMMs were prepared from methylene bis-p-phenyl diisocyanate (MDI), diethylene glycol (DEG) and oligomeric fluoroalcohol, Zonyl BA-LTM of average molecular weight 443 (BAL). The stoichiometric ratio for SMMs synthesis was 3(MDI): 2(DEG): 2(BAL).

Suk et al. [3] later developed new surface modifying macromolecules (nSMM), in which DEG in the earlier work was replaced by aminopropyl poly(dimethyl siloxane) (PDMS). They used these nSMMs together with the host polyethersulfone (PES) to prepare membranes for MD. It is worth mentioning that blending DEG based SMM yielded better DCMD fluxes than blending nSMM [1-3].

In this study further improvement of MD performance was attempted by changing the nSMM structures. To this end, the stoichiometric ratio of nSMM components was altered systematically in nSMM synthesis; i.e. nSMM1 2(MDI):1(PDMS):2(BAL); nSMM2, 3(MDI):2(PDMS):2(BAL); nSMM3: 4(MDI):3(PDMS):3(BAL).

The newly synthesized SMMs were characterized by the gel permeation chromatography and the elemental analysis to know the molecular weight and fluorine content, respectively. The results showed that fluorine content decreased with increasing the PDMS stoichiometric ratio. Furthermore, the newly developed SMMs were blended with PEI host polymer to prepare composite hydrophobic/hydrophilic membranes. This was done in a single casting step by the phase inversion method. The details of membrane casting are as follows. A predetermined amount of PEI was dissolved in dimethylacetimide (DMAc)/g-butyrolactone (GBL) mixture, into which nSMM was added. The composition of

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the polymer dope was PEI (12 wt%), GBL (10 wt%) and nSMM (1.5 wt%) with a balance of DMAc. The resulted mixtures were stirred in an orbital shaker at room temperature for at least 48 h. The polymer dope was cast on a smooth glass plate to a thickness of 0.30 mm using a casting rod at room temperature. Subsequently, the cast film together with the glass plates was immersed for 1 h in distilled water kept at room temperature. The membrane peeled off from the glass plate spontaneously during gelation. All the membranes were then dried at ambient conditions for 3 days.

The membranes were characterized using gas permeation test, measurement of the liquid entry pressure of water (LEPw), scanning electronic microscopy (SEM), and contact angle measurement. The effects of the SMM type on the membrane morphology were identified, which enabled us to link the membrane morphology to the membrane performance.

The membranes were further tested by DCMD for desalination of 0.5 M NaCl solution and the results were compared to commercial polytetraflouroethylene (PTFE) membranes (FGLP 1425, Millipore). nSMM2/PEI membrane yielded the best performance among the tested membranes. In particular, it should be emphasized that the above membrane was superior to the commercial one, which was attributed to the fact that nSMM2/PEI had the highest pore size/porosity ratio and the lowest LEPw among the laboratory made membranes. It is worth mentioning that all the prepared membranes were tested successfully for the desalination application. In other words, no NaCl was detected in the permeate.

The SEM images showed that the laboratory made membranes had similar finger-like structures regardless of the type of the nSMM used. The nSMM2/PEI membrane exhibited macro-voids in the bottom layer, which might have contributed to its DCMD flux that was the highest among all the tested membranes.

A better and instructive understanding of hydrophobic/hydrophilic membrane performance in MD has been obtained by finding the relationship between membrane morphology and membrane performance. This will open a wide avenue to the rational development of novel membranes for membrane distillation.

References

1. M. Khayet, J.I. Mengual, T. Matsuura, J. Membr. Sci., 252 (2005), 101-113.

2. M. Khayet, T. Matsuura, M.R. Qtaishat, J.I. Mengual, Desalination, 199 (2006), 180-181.

3. D.E. Suk, T. Matsuura, H.B. Park, Y.M. Lee, J. Membr. Sci., 277 (2006), 177-185.

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Membrane and Surface Modification III – 6

Friday July 18, 12:15 PM-12:45 PM, Honolulu/Kahuku

Surface Modification of an Aromatic Polyamide Membrane By Self-Assembly of Polyethyleneimine on the Membrane Surface

Y. Zhou (Speaker), University of Waterloo, Waterloo, Canada S. Yu, Zhejiang Sci-Tech University, China C. Gao, The Development Center of Water Treatment Technology, China X. Feng, University of Waterloo, Waterloo, Canada - [email protected]

Reverse osmosis is now a well accepted technique for water and waste water treatment, and interfacially polymerized thin film composite (TFC) polyamide membranes are being used extensively for these applications. Because polyamide membranes are negatively charged under typical operating conditions (pH > 4) due to carboxyl groups on the membrane surface, they are vulnerable to fouling by cationic contaminants. In this study, an aromatic polyamide TFC membrane was modified by electrostatic self-assembly of polyethyleneimine on the membrane surface, and the modified membrane showed significantly improved anti- fouling properties. It was expected that the charge reversal on the membrane surface due to the application of the polyethyleneimine layer would increase the fouling resistance of the membrane to cationic foulants because of the enhanced electrostatic repulsion, and the increased surface hydrophilicity would help minimize the flux reduction. The effects of parameters involved in the membrane surface modification (e.g., polyethyleneimine concentration and deposition time) on the membrane performance were investigated in terms of water permeation flux and salt rejection with and without the presence of decyltrimethylammonium bromide (which is a common cationic surfactant present in waste water). It was shown that the improved fouling resistance and the increased surface hydrophilicity compensated for the reduction in membrane permeability due to the deposition of the polyethyleneimine layer.

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Inorganic Membranes III – 1 – Keynote

Friday July 18, 9:30 AM-10:15 AM, O’ahu/Waialua

Silica Network Engineering For Highly Permeable Hydrogen Separation Membranes

T. Tsuru (Speaker), Hiroshima University, Hiroshima, Japan - [email protected] K. Yada, Hiroshima University, Hiroshima, Japan M. Kanezashi, Hiroshima University, Hiroshima, Japan

Inorganic membranes are promising for possible application to high temperature separation systems and membrane reactor systems [1-3]. Metal membranes, which shows 100% selectivity to hydrogen and high permeances at temperatures, have several disadvantages such as expensive cost, degradation with hydrocarbon and acid gases, and hydrogen brittleness at low temperatures. On the other hand, amorphous silica, which can be derived from the sol-gel processing or CVD (Chemical vapor deposition), is a microporous material, consisting of silica network which allows the permeation of small molecules such as helium and hydrogen. In this paper, recent progress in the control and design of silica network by sol-gel processing will be discussed to develop highly permeable hydrogen separation membranes.

The sol-gel process is divided into two main routes: the polymeric sol-gel route and the colloidal sol-gel route1). In the colloidal sol route where the hydrolysis and condensation reaction of alkoxide (tetraethoxysilane (TEOS) for SiO2 membranes) is fast, the rapid condensation reaction causes particulate growth and/or the formation of precipitates. In the polymeric sol route, the hydrolysis reaction is slower, resulting in a partially hydrolyzed alkoxide and the formation of a linear inorganic polymer. Pore sizes can be controlled by the void spaces among the packed colloidal particles (i. e. interparticle pore) in the colloidal sol route and by the size of the gel network in the polymeric gel route, respectively. By controlling the preparation condition of silica sols (pH, temperature, concentration, aging time etc.), pore sizes of SiO2 membranes were found to be precisely tuned in the subnanometer range. SiO2 membranes showing highly hydrogen selectivity over nitrogen [3], as well as showing a large H2 permeation rate with low H2/N2 but high H2/SF6 separation factors, were successfully prepared [1].

Another strategy to control silica network is the utilization of structured alkoxides, such as (EtO)3-Si-(CH2)n-Si-(OEt)3 (n=1-6). Since the silicone atoms are more distant with each other than the case of TEOS, due to the existence of -C2H4-, the silica network can be expected to be formed more loosely than the case of TEOS. Silica membranes prepared from bis(triethoxysilil)ethane (BTESE, n=2)

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were found to show significantly high permeance (1x10-5 mol m-2 s-1 Pa-1) and high selectivity of H2/SF6 (> 1,000).

[1] T. Tsuru, J. Sol-Gel Sci. Tech., in press.

[2].T. Tsuru, T. Morita, T. Yoshioka, J. Membr. Sci., in press.

[3] R. Igi, T. Yoshioka, Y. Ikuhara, Y. Iwamoto, T. Tsuru, J. Am. Cer. Soc., submitted.

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Inorganic Membranes III – 2

Friday July 18, 10:15 AM-10:45 AM, O’ahu/Waialua

Development of Novel CO2 Affinity-Enhanced Carbon Membranes: Characterization and CO2 Separation Performance

T. Kai (Speaker), Research Institute of Innovative Technology for the Earth (RITE), Kyoto, Japan S. Kazama, Research Institute of Innovative Technology for the Earth (RITE), Kyoto, Japan - [email protected] Y. Fujioka, Research Institute of Innovative Technology for the Earth (RITE), Kyoto, Japan

The concentration of carbon dioxide (CO2), a greenhouse gas, has been increasing in the atmosphere. Several methods have been devised to reduce the amount of CO2 emissions into the atmosphere. Among them, the sequestration of CO2 underground or in the oceans is regarded as one of the promising means to mitigate carbon dioxide emissions. One problem with the sequestration is the cost of recovering CO2 from emissions. For example, chemical absorption, the best-known method of separating and recovering CO2 to date, accounts for more than seventy percent of the entire cost of carbon sequestration. One promising means to lower the cost of CO2 separation is the development of new, high- performance CO2 separation membranes that allow efficient CO2 recovery.

It is well known that carbon membranes shows good CO2/N2 separation performance. To obtain higher separation performance using carbon membranes, it is very important to control CO2 affinity on the pore surface as well as pore size control. In this presentation, we will report on development of novel carbon membranes with enhanced CO2 affinity for CO2 separation to obtain higher CO2 separation performance by incorporating CO2 affinity materials in the pores of the carbon membranes.

Polyimide was chosen as the precursor for carbon membranes. Tubular porous a-alumina membrane (pore diameter: 150nm (symmetric), Outer- diameter: 10mm, inner-diameter: 7mm)) was purchased from Noritake Co., Limited., Japan, and was used as the porous support. The precursor solution was coated on the outer surface of the alumina support by the dip-coating method. After drying, the precursor-coated membrane was carbonized under a N2 atmosphere at 600 degrees centigrade for 3 hours. Alkali metal carbonates (Na2CO3, K2CO3, Rb2CO3, Cs2CO3) and an amine (DL- 2,3-Diaminopropionic acid hydrochloride (DAPA)) were chosen as a CO2 affinity materials. Two preparation methods were examined; Method A (Blend CO2 affinity materials with precursor solution) and method B (Post-treatment, Dip- coating of carbon membranes).

From EDX spectra of the surface of Cs2CO3- incorporated carbon membrane (method A), it was confirmed that the amount of incorporated Cs2CO3 increased

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as the Cs2CO3 concentration in precursor solution increased. In other words, the amount of incorporated Cs2CO3 could be controlled by the Cs2CO3 concentration in precursor solution. From water vapor sorption experiments using carbon film prepared from method A at 40 degrees centigrade, it was found that the shape of sorption isotherm changed as the Cs2CO3 concentration in precursor solution increased. It is suggested that the carbon pores became more hydrophilic by the incorporation of Cs2CO3.

The separation performance was evaluated using a CO2/N2 gas mixture at 40 degrees centigrade. For both method A and method B, separation performance was improved compared with that of the untreated carbon membrane under the humidified conditions.

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Inorganic Membranes III – 3

Friday July 18, 10:45 AM-11:15 AM, O’ahu/Waialua

Electronic Conduction and Oxygen Permeation Through Mixed-Conducting SrCoFeO(x) Membranes

J. Kniep (Speaker), Arizona State University, Tempe, Arizona, USA J. Lin, Arizona State University, Tempe, Arizona, USA - [email protected]

The total conductivity and oxygen permeation properties of dense SrCoFeO(x) membranes synthesized from the solid state method were studied in the temperature range of 700 to 900 degrees C. SrCoFeO(x) powder has been shown to have favorable oxygen adsorption and desorption rates as well as a large oxygen sorption capacity above 800 degrees C. X ray diffraction analysis verifies that the SrCoFeO(x) samples consist of an intergrowth Sr(4)Fe(6-x)Co(x)O(13 + or - delta), perovskite SrFe(1-x)Co(x)O(3-delta), and spinel Co(3-x)Fe(x)O(4) phase. SrCoFeO(x) exhibits n- type and p-type conduction at low and high oxygen partial pressures, respectively, and has a total conductivity of 16.5 S/cm at 900 degrees C in air. SrCoFeO(x) membranes were structurally stable during oxygen permeation experiments with one side exposed to air and the other side exposed to either an inert gas or carbon monoxide. The oxygen permeation fluxes with a carbon monoxide sweep gas were approximately two orders of magnitude higher than the fluxes measured with an inert sweep gas. The highest measured oxygen flux through a 0.80 mm thick SrCoFeO(x) membrane with a carbon monoxide sweep was 4.8 ml/cm2.min at 900 degrees C. The oxygen flux through SrCoFeO(x) membranes was higher than the oxygen flux through SrFeCo(0.5)O(x) membranes of the same thickness under the same experimental conditions.

Asymmetical SrCoFeO(x) membranes consisting of a dense thin layer and a porous support layer of the same material were made using a cold pressing technique. Finely ground powder was used for the dense layer while larger particle sized powder was used for the porous support. The thickness of the dense layer was controlled by using varying amounts of the finely ground powder, with the thinnest dense layer being approximately 150 micrometers. When helium was used as the sweep gas, the critical thickness was determined to be approximately 600 micrometers. When carbon monoxide was used as the sweep gas, the oxygen flux continued to increase as the dense layer decreased down to 150 micrometers due to the more favorable surface kinetics on the sweep side.

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Inorganic Membranes III – 4

Friday July 18, 11:15 AM-11:45 AM, O’ahu/Waialua

Micro-structured Inorganic Membrane Reactor

W. Liu (Speaker), Pacific Northwest National Lab, Richland, Washington, USA - [email protected] Y. Wang, Pacific Northwest National Lab, Richland, Washington, USA D. Elliott, Pacific Northwest National Lab, Richland, Washington, USA X. Li, Pacific Northwest National Lab, Richland, Washington, USA B. Johnson, Pacific Northwest Naitonal Lab, Richland, Washington, USA R. Zheng, Pacific Northwest National Lab, Richland, Washington, USA

Many catalytic reactions are limited by mass transfer or thermodynamic equilibrium. Membranes can be used for in situ regulation of mass transfer rate of reactants or products during a catalytic reaction process to enhance the productivity and/or product yield. Inorganic membranes are suitable for fabrication of membrane reactors due to its high thermal and chemical stability. However, the conventional inorganic membranes made in a single tube or planar disk form has low surface area packing density and is associated with challenges of high cost per unit membrane surface area and low productivity per unit reactor volume. Micro-structured membrane reactor design concepts and prototypes will be discussed in this presentation. In the proposed design, small reaction channels (0.5~3mm) are formed in macro-porous support matrix with the membrane and/or catalyst layer being deposited on the channel wall. The porous matrix plus membrane layer allows selective introduction of reactants from the exterior of the reactor module into the reaction channel or selective withdrawal of products from the reaction channel to the exterior of the reactor module. The small channel enables efficient mixing of the reactants inside the channel and rapid mass transport between the membrane surface and bulk channel fluid. Use of the small channel also provides high membrane surface area packing density. Performance benefits of the novel design will be illustrated with two different types of reaction applications, gas-phase steam reforming for hydrogen production, gas/liquid multiphase hydrogenation for biomass conversion.

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Inorganic Membranes III – 5

Friday July 18, 11:45 AM-12:15 PM, O’ahu/Waialua

Selective Gas Transfer and Catalytic Processes in Nano-Channels of Ceramic Catalytic Membranes

V. Teplyakov (Speaker), A.V.Topchiev Institute of Petrochemical Synthesis, RAS, Moscow, Russia - [email protected] M. Tsodikov, A.V.Topchiev Institute of Petrochemical Synthesis, RAS, Moscow, Russia I. Moiseev, Kurnakov Institute of General and Inorganic Chemistry, RAS, Moscow, Russia

Catalytic processes using of porous ceramics where catalytic coatings on the microchannel walls are of modern interest for creation of high speed (residence time is < 10-3 sec) and compact membrane reactors, especially for C1 reactions. Catalytic mesoporous inorganic membranes combining selective gas transport and catalytic activity can be considered as ‘ensemble’ of nanoreactors and be related to new direction of heterogeneous catalysis. The counter-diffusion transport in catalyst particles is replaced by unidirectional transport with the potential of intensified catalysis and increased selectivity.

Mesoporous ceramic membranes with variation of pore size as non-linear gradient can play an important role for selective mass-transfer control in membrane catalysis. Based on methanol decomposition and methane conversion this paper presents the results demonstrating the intensification of gas phase catalytic processes in nano-channels of ceramic catalytic membranes.

Oxidative condensation of methane was carried out with using tubular ceramic membranes of "BUM" trademark based on titanium carbide with La- Ce/MgO catalyst deposited inside the membrane pores. The methanol conversion was studied using TRUMEM metal-ceramic membranes (TiO2/Stainless steel). For this reaction a Cr2O3×Al2O3×ZnO catalytic coating formed inside the membrane channels was prepared. In latter case additionally a mesoporous layer of single phase oxide P0.03Ti0.97O2±d with a narrow pore size distribution in the range of 2 nm was coated on the top of the catalytic membrane. As a result asymmetric, three- layer ceramic catalytic membranes with a pore gradient in the range of 2- 3000 nm were prepared.

It was found that such membranes possess "directed permeability" in relation to H2, He, CO2, O2, CH4, Ar. The dehydration rate of methanol into formaldehyde and hydrogen directly correlates with selective properties of directed permeability. Productivity of hydrogen under methanol feeding in direction to selective layer through large porous one practically in half-order higher then under contrary direction. Such systems can be considered as membrane-catalytic "diode". Ceramic membranes BUM modified by La-Ce/MgO provide

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improved activity and selectivity in syn-gas production by using partial oxidation of methane under 550-650oC.

It is found that combination of separation selectivity and catalytic activity of ceramic membranes with gradient-porosity can provide intensification of catalytic processes, particularly, for methanol decomposition, oxidative methane conversion and methane gasification by CO2. The latter has good prospects for creation of technology combining consumption of CO2 and methane conversion in one process.

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Inorganic Membranes III – 6

Friday July 18, 12:15 PM-12:45 PM, O’ahu/Waialua

The Oxidative CO2 Reforming of Methane to Syngas in a Thin Tubular Mixed-Conducting Membrane Reactor

C. Zhang (Speaker), Nanjing University of Technology, China X. Dong, Nanjing University of Technology, China W. Jin, Nanjing University of Technology, China - [email protected] N. Xu, Nanjing University of Technology, China

With the increasing global demand for cleaner energy, fuel cell hydrogen and ultraclean gas-to- liquid (GTL) fuels are receiving a great deal of attention as alternative energy sources. Mixtures of H2 and CO, known as synthesis gas, serve as the intermediate between hydrocarbon feedstocks and both hydrogen and GTL fuels. Synthesis gas can be produced by partial oxidation reactions or reforming reactions (steam, CO2, and autothermal), all of which either require or can benefit from pure oxygen as a reactor feed. Because of the high economic, environmental and safety costs associated with pure oxygen, dense mixed- conducting oxygen-permeable membranes have been explored as an alternative oxygen source for methane oxidation process. In this work, the oxidative CO2 reforming of methane (OCRM) to syngas, involving coupling of exothermic partial oxidation of methane (POM) and endothermic CO2 reforming (CRM) processes, was studied on a thin tubular Al2O3 doped SrCo0.8Fe0.2O3-´ (SCFA) membrane reactor packed with a Ni/Al2O3 catalyst. The influences of the temperature and feed concentration on the membrane reaction performances were investigated in detail. The methane conversion and the CO2 conversion were both found to increase with increasing reaction temperature; however, exerted a larger influence on the CO2 conversion. The H2 selectivity was also found to increase with increasing reaction temperature. Depending on the temperature or H2O/CH4, the OCRM process could be performed auto-thermally with idealized reaction condition. Furthermore, OCRM reaction is a green chemistry process owing to its utilization of two greenhouse gases (CO2 and CH4) as a feedstock.

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Facilitated Transport Membranes – 1 – Keynote

Friday July 18, 9:30 AM-10:15 AM, Wai’anae

Facilitated Transport Membrane for Selective Separation of CO2 from CO2-H2 Mixtures at Elevated Temperatures and Pressures

R. Yegani, Kobe University, Kobe, Japan M. Teramoto (Speaker), Kobe University, Kobe, Japan O. Okada, Renaissance Energy Research Company, Osaka, Japan H. Matsuyama, Kobe University, Kobe, Japan - [email protected]

A novel facilitated transport membrane consisting of Cs2CO3 as CO2 carrier and poly (vinyl alcohol)/ poly (acrylic acid) gel (PVA/PAA gel) as support was developed for the removal of CO2 from CO2/H2 mixtures at relatively high pressures (up to 600kPa) and temperatures (125 - 200°C). For this membrane, the presence of water in the membrane is indispensable for the CO2-carrier reaction (overall reaction: CO2 + CO3

2- + H2O = 2HCO3-) to occur rapidly and also for the gel layer to swell so that gas permeation is facilitated. Therefore, very hygroscopic PVA/PAA gel was used as membrane material. The membrane was prepared by casting an aqueous solution of Cs2CO3 and PVA/PAA copolymer onto a hydrophilic microporous PTFE membrane followed by heat treatment. In this membrane, the PTFE membrane pores are filled with the gel and its surface is covered with the gel, which makes the membrane very stable. The membrane performance was tested mainly at 160° C by the experiments on the selective separation of CO2 from a mixture of 5% CO2, 45% H2 and 50% H2O with argon as sweep gas. The sweep side pressure was usually 20kPa lower than the feed side pressure. With increasing the feed side pressure, CO2 permeance increased due to increased water content in the membrane gel layer caused by increased H2O partial pressure. The highest CO2 permeance, 2x10-4 mol/(m2 s kPa), was obtained at 160C when the Cs2CO3 concentration in the gel layer (dry basis) was about 70wt%, and the CO2/H2 selectivity was 125. The highest CO2 permeance and CO2/H2 selectivity were observed at 160C. This may be explained by slower CO2-carrier reaction rate at lower temperatures and lower water content in the gel as well as lower chemical equilibrium constant of the reaction at higher temperatures. However, even at 200C, the observed CO2 permeance was still high (1x10-4 mol/(m2 s kPa)) and the CO2/H2 selectivity was about 80. It was found that the higher the humidity of the feed gas, the higher both CO2 permeance and CO2/H2 selectivity, which also suggests the importance of water content in the membrane. Crosslinking of gel layer by glutaraldehyde was found to be effective to decrease H2 permeation rate by minimizing the defect (pinhole) formation. The highest CO2/H2 selectivity was as high as 650 with almost the same CO2 permeance as that observed with the membrane without crosslinking. This membrane was found to be stable during a long-term experiment for 350 h. As far as we know, the resent membrane has the highest CO2 permeance and

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CO2/H2 selectivity at high temperatures. This type of membrane has a potential for use as CO2 selective membrane in a water-gas shift membrane reactor and also for CO2/N2 separation at high temperatures such as CO2 separation from hot flue gases.

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Facilitated Transport Membranes – 2

Friday July 18, 10:15 AM-10:45 AM, Wai’anae

Explorative Investigation of Cu(II) Facilitated Transportation Through Supported Liquid Membrane and Its Derivatively Successful Story

Q. Yang (Speaker), National University of Singapore, Singapore T. Chung, National University of Singapore, Singapore - [email protected] J. Jiang, National University of Singapore, Singapore N. Kocherginsky, National University of Singapore, Singapore

The initiative for this work is to develop a novel and more efficient supported liquid membrane (SLM) based process to recover copper and regenerate spent ammoniacal etchant solution with low operation cost and without generating secondary waste for Printed Circuit Board (PCB) manufacturers. A comprehensive study has been conducted in this work including 1) the quantum chemical computations for selecting proper carrier for Cu(II) extraction in SLM system; 2) the fundamental kinetics and mechanism of Cu(II) transport through SLM system; 3) a successful lab-scale to pilot-scale spent etchant treatment process.

First of all, a comparative study of two widely used Cu(II) extractants, namely LIX54 and LIX84, and their impregnated SLM systems was carried out in this work. Experimental and computational characterizations of LIX54/Cu(II) and LIX84/Cu(II) complexes were investigated and the results agreed well in the reaction mechanisms, complexes geometries and Cu(II) extraction strengths of these two carriers. Cu(II) transmembrane fluxes at different conditions were compared and the results showed that LIX54 had slightly higher copper removal rate in the ammoniacal solution but much poorer copper loading in acidic media. Much higher selective separation performances of Cu(II) over Zn(II) and Cd(II) and no ammonia carry-over provide LIX54 significant advantages over LIX84 for ammoniacal solutions treatment.

Subsequently, Cu(II) recovery from industrial ammoniacal wastewater using flat sheet SLM system was investigated. LIX54 in kerosene was used as a carrier in the liquid membrane phase to extract and transfer copper. Detailed theoretical model for facilitated transport through flat membrane was developed, where diffusion of copper complex with ammonia in aqueous stagnant layer and fast reactions of the carrier and copper species in aqueous reaction layer have been taken into account. This model, where the carrier moves slightly out from the membrane in the reaction layer, then transfers from one aqueous phase to another through the membrane, and finally moves back, is called Big Carrousel. Mathematical model simulation demonstrated that only Big Carrousel model, based on the ability of the carrier to leave the membrane and to react with copper

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ammonia complexes in aqueous solutions, gives satisfactory quantitative description of all experimental results, including the flux plateau at high feed copper concentrations and the decrease of copper flux at lower pH of the feed solutions. This is for the first time an experimental work demonstrating the applicability of this transportation mechanism.

Relied on the above-mentioned fundamental studies, the successful bench scale to pilot scale tests were accomplished. The treatment process based on SLM technology resulted in Cu(II) removal from spent ammoniacal etching solution and formation of saturated copper sulfate solution in sulfuric acid, used as a striping phase. Composition of the regenerated etching solution and purity of CuSO4‡5H2O crystals formed in the striping phase were comparable or even better than their commercial analogues.

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Facilitated Transport Membranes – 3

Friday July 18, 10:45 AM-11:15 AM, Wai’anae

Ionic Liquid Membranes for Carbon Dioxide Separation

C. Myers (Speaker), US DOE, National Energy Technology Laboratory, Pittsburgh, Pennsylvania, USA - [email protected] J. Ilconich, Parsons, South Park, Pennsylvania, USA H. Pennline, US DOE, National Energy Technology Laboratory, Pittsburgh, Pennsylvania, USA D. Luebke, US DOE, National Energy Technology Laboratory, Pittsburgh, Pennsylvania, USA

Recent scientific studies are rapidly advancing novel technological improvements and engineering developments that demonstrate the ability to minimize, eliminate, or facilitate the removal of various contaminants and greenhouse gas emissions in power generation. The Integrated Gasification Combined Cycle (IGCC) shows promise for carbon dioxide mitigation not only because of its higher efficiency as compared to conventional coal firing plants, but also due to a higher driving force in the form of high partial pressure. One of the novel technological concepts currently being developed and investigated is membranes for carbon dioxide (CO2) separation, due to simplicity and ease of scaling. A challenge in using membranes for CO2 capture in IGCC is the possibility of failure at elevated temperatures and pressures. Our earlier research studies examined the use of ionic liquids on various supports for CO2 separation over the temperature range 37-300°C. The ionic liquid, 1-hexyl- 3methylimidazolium Bis(trifluoromethylsulfonyl) imide, ([hmim][Tf2N]), was chosen for our initial studies with the following supports: polysulfone (PSF), poly(ether sulfone) (PES), and cross- linked nylon. The PSF and PES supports had similar performance at room temperature, but increasing temperature caused the supported membranes to fail. The ionic liquid with the PES support greatly affected the glass transition temperature, while with the PSF, the glass transition temperature was only slightly depressed. The cross-linked nylon support maintained performance without degradation over the temperature range 37-300°C with respect to its permeability and selectivity. However, while the cross-linked nylon support was able to withstand temperatures, the permeability continued to increase and the selectivity decreased with increasing temperature. Our studies indicated that further testing should examine the use of other ionic liquids, including those that form chemical complexes with CO2 based on amine interactions. The hypothesis is that the performance at the elevated temperatures could be improved by allowing a facilitated transport mechanism to become dominant. Several amine-based ionic liquids were tested on the cross-linked nylon support. It was found that using the amine- based ionic liquid did improve selectivity and permeability at higher temperatures. The hypothesis was confirmed, and it was determined that the type of amine used also played a role in facilitated transport. Given the appropriate aminated ionic liquid with the cross-linked nylon support, it is

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possible to have a membrane capable of separating CO2 at IGCC conditions. With this being the case, the research has expanded to include separation of other constituents besides CO2 (CO, H2S, etc.) and if they play a role in membrane poisoning or degradation. This communication will discuss the operation of the recently fabricated ionic liquid membranes and the impact of gaseous components other than CO2 on their performance and stability.

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Facilitated Transport Membranes – 4

Friday July 18, 11:15 AM-11:45 AM, Wai’anae

CO2 Capture: Reduction in Greenhouse Gas Levels

D. Smith, Carbozyme, Inc., Monmouth Junction, New Jersey, USA R. Cowan, Carbozyme, Inc., Monmouth Junction, New Jersey, USA M. Trachtenberg (Speaker), Carbozyme, Inc., Monmouth Junction, New Jersey, USA - [email protected]

Separation of flue gas carbon dioxide (CO2) from natural gas, petroleum or coal fired furnaces is the single most difficult and expensive step (>65% of total) in the capture-transport-geologic storage scenario proposed by national and international organizations focused on control of greenhouse gases. The object, as laid out by the DOE National Energy Technology Laboratory (NETL), is to extract 90% of the CO2 to yield 95% purity with an energy penalty of less than 20% for the stream derived from combustion of pulverized coal and to have the scalability to manage a gas flow of thousands of cubic meters (hundreds of thousands of cubic feet) each day.

We have been developing an enzyme-based, contained liquid membrane (CLM), dual hollow fiber permeator for this purpose. The key next step is progressive scale up of this design and testing with actual flue gas under development facility conditions in anticipation of later, yet larger, pilot scale field trials. The design and operation of the permeator is critical to maximizing performance. However, a multiple hollow fiber design of the type we developed has not been demonstrated before nor has it been manufactured commercially. Key elements to successful design are: " Thermal regulation as the evaporation of large quantities of water will affect operating temperature. Control of this temperature by circulating the CLM will affect system selectivity and CO2 recovery. Lack of control of this temperature will result in condensation within the hollow fibers and/or membrane pores. " Uniformity of thermal management effects driving forces for system flow. " Permeate pressure control is necessary to minimize the energy burden imposed by the capture system. However this will effect CO2 recovery and have an effect on selectivity.

Each of these issues has now been addressed. Process engineering studies and system simulations provide the basis for size selection.

Modeling of the effect of pulverized coal fired flue gas components on the CLM has been carried out to determine the flue gas component acceptance values as well as the preferred gas flow rates, pressure and temperature. Modeling has been used to design post-capture treatment to provide a stream that satisfies pipeline acceptance values. Primary interest is on the micro components of PC

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fired boiler flue gas, SOx and mercury. These components will have significant effects on the permeator function and there control before admission to the permeator is important. Acceptance criteria for them have been established.

To date, using smaller, laboratory scale devices, we have studied both analog (ersatz) streams and flue gas derived from combusting methane or propane. The feed gas CO2 concentration ranged from 0.05- 40% in air, and 6%-13% derived from burning hydrocarbon fuels. Feed gas source or composition did not affect CO2 permeance. The solubility of each non-reactive gas in the solvent liquid alone determined the specific permeance and thus the selectivity. For coal (natural gas) feed streams will contain about 13.8% (3.5%) CO2; the retentate, returned to the stack, are expected to contain 1.6% (0.4%) CO2, while the dry compressed product is 94.9% (89%) CO2 for a given permeator design. We are in process of determining the actual operation values. The status will be discussed.

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Facilitated Transport Membranes – 5

Friday July 18, 11:45 AM-12:15 PM, Wai’anae

Novel Olefin Carrier for Facilitated Transport Membranes: Partially Polarized Surface of Silver Nanoparticles by Electron Acceptor

Y. Kang (Speaker), Hanyang University, Korea - [email protected] S. Kang, Seoul National University, Korea

A new application of metallic silver nanoparticles as a novel olefin carrier for facilitated olefin transport membranes was explored. The surfaces of silver nanoparticles were chemically activated using electron acceptor such as p-benzoquinone. The chemically activated surface is expected to form complexes with olefin molecules resulting in olefin carrier for facilitated transport. Such facilitated transport membranes were applied for separation of olefin/paraffin mixtures such as propylene/propane mixtures. The separation performance for the 50/50 (v/v) propylene/propane mixture through the 1/1/0.85 EPR/AgO/ p-benzoquinone membrane showed the selectivity of 10 and the mixed gas permeance of 0.5 GPU for up to 105 hrs. The change in the chemical environment around the silver nanoparticles in EPR/Ago composite membranes upon the incorporation of p-benzoquinone was investigated by XPS. The binding energy of the d5/2 orbital of the silver particle in the EPR/Ago/p-benzoquinone system increased gradually with increasing p-benzoquinone content. This indicates that the binding energy of the valence electrons in the silver atoms increased due to the interactions between the silver atoms and p-benzoquinone, and that the surface of the silver nanoparticles was partially positively charged. Quantum mechanical ab-initio calculations were conducted to confirm the possible theoretical interactions between the surface of the silver nanoparticles and olefin molecules. Ethylene molecules can interact with the upper edge, the side, or the palm side of the silver nanoparticle with corresponding complexation enthalpies (”H) of -4.48, -3.65 and -1.42 kcal/mol, respectively. These ab-initio calculations suggest the presence of the interactions between the silver nanoparticle and olefin molecules, with the most probable interaction of ethylene with the upper edge of the silver nanoparticle. The complexation of propylene with the surface of the silver nanoparticles was investigated using FT-IR spectroscopy. The EPR/Ago composite without p-benzoquinone showed two peaks at 1664 and 1640 cm-1 representing the C=C stretching vibration of propylene (Å1 and Å2 of C=C in free propylene are 1664 and 1640 cm-1, respectively), upon exposure to propylene. The positions of the peaks remained unchanged as the exposure time was increased up to 30 minutes. The two propylene peaks disappeared in the spectra following desorption of propylene for 5 minutes. These results suggest no interaction of propylene with the surface of the silver nanoparticles in the EPR/Ago composite without p-benzoquinone as the propylene absorption occurs only in the EPR matrix. On the other hand, the

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EPR/Ago/p-benzoquinone composite showed peaks at 1664 and 1640 cm-1 right after propylene exposure. The intensities of the both peaks at 1664 and 1640 cm-

1 decreased and a new peak at 1649 cm-1 became dominant with increasing propylene exposure time. These results indicated that the new peak at 1649 cm-1 was presumably due to the partial electron transfer from the C=C bond of propylene to the partially positively charged surface of the silver nanoparticles. Conclusively this is the first attempt to use silver nanoparticles activated by an electron acceptor such as p-benzoquinone as olefin carriers for facilitated transport. The activated or partially positively charged surface of silver nanoparticles caused interactions or complexation with olefin molecules, such as propylene and ethylene, as supported by FT-IR spectroscopy and ab-initio calculations.

Reference

(1) Y. S. Kang, S. W. Kang, H. Kim, J. H. Kim, J. Won, C. K. Kim, and K. Char, Advanced Materials, 2007, 19, 475-479

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Facilitated Transport Membranes – 6

Friday July 18, 12:15 PM-12:45 PM, Wai’anae

Selectivity and Stability of Facilitated Transport Membranes Containing Silver Nanoparticles for Propylene Separation

L. Pollo (Speaker), Federal University of Rio de Janeiro, Rio de Janeiro, Brazil A. Habert, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil C. Borges, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil - [email protected]

Propylene is the key building block for the production of important petrochemical products, such as polypropylene, acrylonitrile, propylene oxide, cumene, phenol, isopropylic alcohol and many others. The worldwide demand for propylene has been increasing at 5.7% a year since 1990, with a forecast of 84 million tons for 2010. To obtain propylene many successive stages of distillation are necessary, the separation of propane and propylene being the most difficult and expensive. With close molecular sizes and relative volatility, distillation towers must run at high rates of reflux extreme pressure and temperature conditions, with a high energy cost.

Polymeric membranes have long been used in the separation of mixtures, like oxygen from air, carbon dioxide from methane, and the dehumidification of air amongst others. Nevertheless, conventional polymeric membranes are not competitive for the separation of olefin/paraffin mixtures, due to an unfavorable tradeoff of selectivity and permeability. Similar physicochemical properties and molecular size of these compounds are indeed limitations for membrane separation based on sorption/diffusion mechanism. One alternative that has been sought is a simultaneous increase of permeability and selectivity by incorporating in the membrane matrix specific agents that interact reversibly with propylene but not with propane. In this way, propylene permeation occurs by facilitated transport mechanism.

Our research group has been investigating silver salts as propylene carriers, obtaining very good results. However, silver salts have a low chemical stability resulting in the loss of transport activity over long periods of time. In order to overcome this problem, this work investigates the use of metallic silver nanoparticles in polyurethane composite membranes. Metallic nanoparticles have attracted much attention due to their unique physicochemical properties.

The silver nanoparticles were photogenerated in situ in the polyurethane matrix using UV light radiation and AgCF3SO3 salt as precursor. The composite membrane was prepared by coating a commercial microfiltration membrane of nylon. It was observed an improved stability of silver nanoparticles, which may

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related to the presence of free electrons in functional groups of the polymer chain. The membranes also showed excellent performance for propylene/propane separation at 25ºC and 4 bar. A propylene/propane ideal selectivity of 100 and propylene permeability of 4 GPU were obtained. After 180 hours of continuous permeation, the membrane performance still was unchanged.

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Oral Presentation Abstracts

Afternoon Session

Friday, July 18, 2008

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Pervaporation and Vapor Permeation III – 1 – Keynote

Friday July 18, 2:15 PM-3:00 PM, Kaua’i

Vapor Permeation and Pervaporation as Efficient Alternatives in the Recovery of Fruit Aroma Compounds

N. Diban, University of Cantabria, Stantander, Spain A. Urtiaga, University of Cantabria, Stantander, Spain I. Ortiz (Speaker), University of Cantabria, Stantander, Spain - [email protected]

Flavours or aroma compounds are key components for the fruit juice industry. They confer the characteristic scent and taste attributes to the product determining the customers acceptance. During the concentration process, aroma compounds are usually lost and they are recovered by distillation in order to add them back to the final product. Nevertheless, the heat applied during this stage may cause important degradation and losses of volatile aroma compounds, additionally to the high energy consumption that this procedure implies.

Membrane processes are very attractive to be applied in aroma recovery because they are simple and flexible, employ mild working temperatures and do not need chemical additives. Moreover, they are characterised by low energy consumption and easy scaling-up [1]. From the possible membrane- based technologies, Pervaporation (PV) [2] and Vacuum Membrane Distillation (VMD) [3] were selected.

Identification of the characteristic aroma compounds present on real fruit juices has been made by means of GC-MS. From this analysis, supported by the literature [5], it was determined that the impact aroma compound of pear was ethyl 2, 4-decadienoate (DEC) and for bilberry, it was trans-2-hexen-1-ol (HEX). They belong to different functional groups (esters and alcohols, respectively) and own different characteristic properties (i.e., saturation pressure, solubility in water, hydrophobicity).

While for PV, the membrane mass transfer across dense polymer material is always due to a solution- diffusion phenomenon, in VMD, because of the porous membrane, mass transfer can occur by vapour permeation through the porous membrane and/or solid transport in the non-porous section of the membrane, depending on the compound/membrane affinity.

In this work the comparative analysis of the behaviour of PV and VMD for the separation and concentration of the mentioned two aroma compounds using hydrophobic membranes has been made. PV of trans-2-hexen-1-ol on polydimethylsiloxane (PDMS) membranes and VMD of ethyl 2, 4-decadienoate on polypropylene (PP) membranes were studied for a ternary model system of

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water/ethanol/aroma compound. Operational variables (aroma compound feed concentration, feed flow rate, temperature and downstream pressure) affecting the process performance (i.e. partial fluxes and enrichment factors) were studied. Efforts were directed to the development of mathematical models that allow the process design and simulation. The characteristic mass transfer mechanism and parameters for each system, consisting on a membrane technology and an aroma compound feed solution, were experimentally determined [6-8]. On one hand, for the PV of HEX, the classical solution-diffusion mass transport mechanism across the membrane was found and its characteristic solubility, Si, and diffusivity, Ds,i, parameters were obtained. On the other hand, experimental results showed that during the VMD of DEC, similarly to PV, solution and surface diffusion of the aroma compound onto the PP membrane occurred, while for the major components of the feed solution the mass transfer took place by means of classical vapour permeation.

During the experiments of VMD for the concentration of DEC, the aroma compound enrichment factor, bDEC, reached a value up to 15. Whereas in PV, the bHEX achieved was approximately 200 at the most favourable experimental working conditions. The mathematical models previously developed have been used in the analysis of operative conditions and parameters in the comparative behaviour of the technologies for the two study cases. Both technologies show feasibility and a great potential for aroma compound recovery.

Acknowledgements Projects CTM2006-00317 and CTQ2005-02583 of the Spanish Ministry of Education and Science and F.P.I. grant are gratefully acknowledged.

Literature

[1] V.Calabro, B.L.Jiao and E.Drioli, Theoretical and experimental study on membrane distillation in the concentration of orange juice, Ind & Eng Chem Res, 33 (1994) 1803.

[2] C.C.Pereira, C.P.Ribeiro, R.Nobrega and C.P. Borges, Pervaporative recovery of volatile aroma compounds from fruit juices. J Memb Sci 274 (2006) 1.

[3] R.Bagger-Jørgensen, A.S.Meyer, C.Varming and G.Jonsson, Recovery of volatile aroma compounds from black currant juice by vacuum membrane distillation. J Food Eng 64 (2004) 23.

[4] I.D.Morton & A.J.Macleod. Food flavours. Part C. The flavour of fruits. Elsevier, Amsterdam, 1990.

[5] N.Diban, A.Urtiaga, I.Ortiz. Recovery of key components of bilberry aroma using a commercial pervaporation membrane. Desal 224 (2008) 34.

[6] V.García, N.Diban, D.Gorri, R.Keiski, A. Urtiaga, I. Ortiz. Separation and concentration of bilberry impact aroma compound from dilute model solution by pervaporation. JCTB, accepted.

[7] N. Diban, O.C. Voinea, A. Urtiaga,I. Ortiz. Vacuum Membrane Distillation of the main pear aroma compound: experimental study and mass transfer modelling. J Mem Sci, under review.

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Pervaporation and Vapor Permeation III – 2

Friday July 18, 3:00 PM-3:30 PM, Kaua’i

Monitoring and Modelling of Aroma Recovery from Fermentation Media Using Pervaporation and Fractionated Condensation

C. Brazinha (Speaker), Universidade Nova de Lisboa, Caparica, Portugal - [email protected] O. Teodoro, Universidade Nova de Lisboa, Caparica, Portugal J. Crespo, Universidade Nova de Lisboa, Caparica, Portugal

Introduction

Organophilic pervaporation has a high potential for aroma recovery from dilute aqueous solutions because it involves a low energy input when compared with other separation processes such as distillation. Also, it operates at mild conditions allowing a direct recovery of aroma compounds from fermentation processes or biological complex media.

Mass spectrometry (MS) proves to be a powerful analytical tool for studying the recovery and fractionation of aromas using pervaporation-condensation systems because it allows for on-line monitoring of the concentration of each vapour present in the permeate stream. Due to its high sensitivity and precision, MS is particularly suitable for on-line monitoring of aromas present in trace concentrations. It also enables transient studies and reduces experimental workload significantly when compared with conventional gas chromatography analysis.

Previous work proved that MS can successfully on-line monitor pervaporation processes under variable upstream conditions [1]. The present work aims to extend the use of this technique for processes with variable temperature of condensation and downstream pressure.

Aroma recovery both from fermentation media (e.g. for valorisation of aromas as by-products of the bio-ethanol production) and also from other biological media is not an easy task since aromas are usually dilute in a complex mixture (aroma profile). Fractionation of aromas is important to consider when we are interested in a particular aroma or group of aroma compounds. Aiming at defining suitable strategies for recovery and fractionation of aromas, in order to obtain pre-defined condensates, a mathematical model was developed and experimentally validated. This model allows for optimisation of the temperature in first condenser, in a pervaporation process using in-series condensation. This model also applies successfully to media where ethanol and dissolved gases (carbon dioxide) are present.

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Experimental

The experimental set-up involves a pervaporation cell and two condensers in series operated under controlled vacuum and temperature. A POMS-PEI membrane gently provided by GKSS, Germany was used. For on-line MS monitoring, the partial permeate pressure of each compound i is acquired in real-time. The permeate is sampled through a split line with a needle valve. Previously, independent mono component calibrations were obtained in order to correlate the characteristic MS signal of compound i with its partial permeate pressure.

Results

The experimental work developed for validation of the MS monitoring technique was performed with the MS coupled to the pervaporation-condensation system, varying the temperature in the first condenser. This work allowed to define suitable operating conditions where the MS signals were sensitive, reproducible and independent, validating the MS as an on-line monitoring tool.

The mathematical model we developed was based on phase equilibrium in the condensers and it allowed us to obtain pre-defined condensates using Pervaporation and Condensation-in-series under constant operating conditions, such as upstream conditions and permeate pressure. The model allows for prediction of the percentage of condensation of each compound and the composition of the condensates in each condenser, at variable temperature in the condenser. After an independent measurement of dissolved gases, the model was firstly developed for systems with water and different amounts of dissolved gas as feed solution, taking into account inert gas permeation. The effect of inert gases on the performance of the condensation process are discussed comprehensively and predicted mathematically. This model was also applied to complex feed streams: dilute aroma compounds in aqueous solutions and dilute aroma compounds in hydro alcoholic solutions, comprising different amounts of dissolved gas. In all steps, with increasing complexity of the feed solution, this modelling toolbox was experimentally validated and the results obtained interpreted. As a final result, the model developed proved to be adequate to all feed streams studied, including feed solutions with complex composition, as happens in biological and fermentation media (with ethanol and dissolved gases).

This model enables to predict correctly the degree of condensation of the different feed components as a function of the condenser’s temperature, making possible the design of the best strategies for aroma recovery and fractionation.

References

[1] T. Schäfer, J. Vital and J.G. Crespo, Coupled pervaporation/mass spectrometry for investigating membrane mass transport phenomena, J. Membrane Sci., 2004, 241 (2004) 197.

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Pervaporation and Vapor Permeation III – 3

Friday July 18, 3:30 PM-4:00 PM, Kaua’i

Effect of Feed Solution Characteristics on Flavour Concentration by Pervaporation

A. Overington (Speaker), Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand - [email protected] M. Wong, Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand J. Harrison, Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand L. Ferreira, Fonterra Co-operative Group Ltd., Auckland, New Zealand

Organophilic pervaporation can potentially be used in the food industry to recover flavours that would otherwise be lost, and to create natural flavour concentrates. Trials with model solutions often show that flavour compounds can be highly enriched using pervaporation, but there has been little research on how the process is affected by non-volatile substances found in foods, such as fat, protein and carbohydrates. These components cannot pass through pervaporation membranes, but they can interact with flavour compounds in the feed.

The driving force for pervaporation depends on the activity of each permeant on the feed side of the membrane. Non-volatile feed components can either increase or decrease permeant activities, following various mechanisms. In a food product that contains fat, flavour compounds will partition between the aqueous and fat phases. The partition coefficient between the two phases depends on the compound. The portion of each compound in the fat phase is effectively unavailable for pervaporation. Protein and carbohydrates can also alter flavour compound volatility by different amounts depending on the compound, thereby changing the driving force for pervaporation of these compounds. The driving force of acidic compounds is also affected by the feed pH.

To bridge the gap between model solution trials and pervaporation of real food products, it is important to understand how feed solution characteristics affect pervaporation. This presentation presents results from the pervaporation of selected flavour compounds (homologous series of organic acids, esters and ketones) in feed solutions containing dairy ingredients (cream, lactose and milk protein).

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Pervaporation and Vapor Permeation III – 4

Friday July 18, 4:00 PM-4:30 PM, Kaua’i

Concentration of Bioethanol By Porous Hydrophobic Membranes

T. Uragami (Speaker), Kansai University, Osaka, Japan - [email protected]

Porous poly(dimethylsiloxane) (PDMS) membranes were prepared by freeze drying aqueous emulsions of organopolysiloxane for the concentration of aqueous solutions of dilute ethanol which are produced from the fermentation of biomass. This paper introduces the preparation of porous PDMS membranes and the development of a new membrane separation technique for the concentration of bioethanol. Porous PDMS membranes were applied to a temperature- difference controlled evapomeation (TDEV) method developed as a new membrane separation technique that can be controlled temperatures of the feed solution and the membrane surroundings. When the temperature of the feed solution was kept constant but the temperature of membrane surroundings was lowered, the ethanol/water selectivity increased remarkably and the permeation rate decreased. The ethanol/water selectivity of a porous PDMS membrane in TDEV operation was almost equal to that of a dense PDMS membrane in TDEV, however, the permeation rate of the porous membrane was higher by three orders of magnitude. The permeation and separation mechanisms for aqueous ethanol solutions through porous PDMS membranes in TDEV were discussed as follows.

When water and ethanol molecules, vaporized from the feed solution, come close to the membrane surroundings kept at lower temperature in TDEV, the water vapor aggregates much easier than the ethanol vapor, because the freezing point of water molecules is much higher than that of ethanol molecules, and the aggregated water molecules tend to be liquefied as the temperature of the membrane surroundings becomes lower. On the other hand, because the PDMS membrane has a relatively high affinity to the ethanol molecules, they are sorbed inside the pores in a porous PDMS membrane and this sorbed layer of the ethanol molecules is formed in an initial stage of the permeation. The vaporized ethanol molecule may be able to permeate across the membrane by surface diffusion on the sorbed layer of the ethanol molecules inside the pores.

Both the aggregation of the water molecules and the surface diffusion of the ethanol molecules in the pores are responsible for the increase in the ethanol/water selectivity through a porous PDMS membrane in TDEV. The increase of the ethanol/water selectivity in TDEV can be attributed to both the degree of aggregation of the water molecules on the membrane surroundings and the thickness of the sorbed layer of the ethanol molecules inside the pores, which are significantly governed by the temperature of the membrane

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surroundings. When the temperature of the membrane surroundings becomes lower, the degree of aggregation of the water molecules and the thickness of the sorbed layer of the ethanol molecules are increased. Therefore, an increase in the ethanol/water selectivity for aqueous ethanol solutions was observed with decreasing temperature of the membrane surroundings.

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Pervaporation and Vapor Permeation III – 5

Friday July 18, 4:30 PM-5:00 PM, Kaua’i

Treatment of Gas Containing Hydrophobic VOCs by a Hybrid Absorption-Pervaporation Process: The Case of Toluene

F. Heymes, LGEI, Ecole des Mines d'Ales, Ales, France P. Manno-Demoustier, LGEI, Ecole des Mines d'Ales, Ales, France J. Fanlo, LGEI, Ecole des Mines d'Ales, Ales, France E. Carretier (Speaker), Université Paul Cézanne Aix Marseille, Provence, France - [email protected] P. Moulin, Université Paul Cézanne Aix Marseille, Provence, France

Recent legislation encourages industrialists to set up equipment for treating their VOC-loaded gaseous effluents. For hydrophobic components such as toluene, poor solubility in water requires specific absorbent. This work contributes to the development of a hybrid absorption-pervaporation process to treat gases containing hydrophobic compounds by coupling absorption and in-situ membrane-based regeneration. The approach can be split into several parts. The first part aimed to review hydrophobic absorption knowledge to determine an efficient absorbent. Four chemical classes were tested (i) polyethylene glycols, (ii) phthalates (iii) adipates and (iv) silicon oil. Experiments were performed to check gas-liquid partitioning and viscosity. All missing experimental data were determined, and this allowed selection of di(2- ethylhexyl) adipate (DEHA) as the most attractive absorbent. Influence of temperature was correlated in the range (20 to 70) °C. DEHA was shown to be efficient in other aromatic and chlorinated VOCs. The second part examined the hydrodynamics and mass transfer of a packed column fed with DEHA to eliminate the toluene from a medium- concentration gaseous effluent (0.5-5g.m-3). The hydrodynamic study showed that the viscosity of DEHA was not a technical obstacle to its implementation in an industrial column. The absorption of toluene by DEHA showed the efficiency of this process. But, this efficiency decreases quickly when the washing liquid becomes loaded with toluene. From the point of view of mass transfer modelling, we showed that mass transfer is limited by liquid-side resistance, which seems logical since DEHA is a viscous absorbent. Our experimental results showed that the kLa of the system depends on the liquid speed but also on the gas speed. This behaviour has also been observed by the few authors who have used viscous fluids in their experiments, but runs counter to all the authors who have work on low-viscosity fluids: generally, they do not take into account the gas speed. During the third pervaporation part, bibliographical research and a preliminary theoretical evaluation led to the choice of PDMS for separating the toluene / absorbent mixture, whatever the absorbent. PDMS has a high affinity for toluene and a lower affinity for the different absorbents. The permeability of the toluene was evaluated at 25°C and confirmed the potential of PDMS for recovering toluene. Experiments led with the various pure absorbents showed

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that no absorbent was detected in the filtrates. In the case of toluene-absorbent mixtures (10 g.L-1), results led to the conclusion that DEHA would be the most easily regenerable absorbent. Experimental pervaporation flows at low toluene concentrations (< 10 g.L-1) were very low. The predominant effect of the liquid boundary layer was highlighted. Liquid hydrodynamics upstream of the membrane therefore seem to be the major parameter. The tubular module was intended to study this question rigorously. Pervaporation was investigated to regenerate a heavy absorbent containing toluene at low concentrations (< 10 g.L-

1). This process was chosen because of thermal decomposition of heavy absorbents by distillation and absorbent loss by stripping. The resistance-in-series theory allowed the impact of the boundary layer to be quantified. The flow rates of toluene extraction from a DEHA solution were low and require improving the pervaporation regeneration performance to use this kind of separation in an industrial hybrid process. The hybrid process was coupled in function of three values: flow rate, temperature, concentration. The concentration of toluene in the absorbent has a determining effect on the efficiency of the overall process. However, it is not a directly adjustable parameter, unlike temperature and flow rate. Temperature has opposite effects on the efficiency of the two steps in the process, which means either finding an optimum compromise or dithermal operation (different temperatures for the absorption column and pervaporation module). Important information was provided by formulating the equations of the system and using the correlations determined. It was shown that there were multiple possible membrane surface area / column height compromises for treating a given gaseous effluent. Any increase in membrane surface area can be compensated by a decrease in column height (operating at low global toluene concentrations in the liquid phase). Inversely, a high column enables a lower membrane surface area to be used (operating at high global toluene concentrations in the liquid phase). Calculating the initial investment and operating costs will enable the user to choose the best compromise between column height and membrane surface area.

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Drinking and Wastewater Applications V – 1 – Keynote

Friday July 18, 2:15 PM-3:00 PM, Maui

The Development of a Household Ultrafiltration System for Developing Countries

M. Peter-Varbanets (Speaker), Eawag - Swiss Federal Inst. of Aquatic Science and Technology, Duebendorf, Switzerland - [email protected] M. Vital, Eawag - Swiss Federal Inst. of Aquatic Science and Technology, Duebendorf, Switzerland F. Hammes, Eawag - Swiss Federal Inst. of Aquatic Science and Technology, Duebendorf, Switzerland W. Pronk, Eawag - Swiss Federal Inst. of Aquatic Science and Technology, Duebendorf, Switzerland

Global assessments by the WHO and UNICEF showed that one-sixth of the world's population did not have access to safe water for drinking at the beginning of 2000. A huge effort is required in order to reach the drinking water objectives set out in the Millennium Development Goal: to half the proportion of population without sustainable access to safe drinking water and sanitation by 2015 as compared to 1990. A part of the solution is the application of decentralized Point-of-use (POU) treatment systems. This solution is already practiced in some areas, but available systems are often cost-intensive and require time consuming maintenance. In principle, membrane technology is also attractive for such applications because it provides absolute barriers for controlling hygiene hazards and its modular construction allows implementation on all possible scales. Furthermore, the costs of the membrane itself have decreased significantly in the last decades. However, the application of UF technology in DC and TC is limited by other factors. The basic principle of operation of traditional large scale UF water treatment plant is to assure high flux avoiding large membrane surfaces. Therefore, frequent chemical cleaning are usually applied and transmembrane pressures are in the order of 0.5 - 1.0 bar. For application in households in developing and transition countries, the application of pumps and chemicals, as well as complex operation schemes should be avoided. Therefore, we focused on developing a low-pressure, gravity-driven membrane system without the use of cleaning chemicals. The system was operated at pressures between 40 and 110 mbar. This corresponds to a water column of 0.40 - 1.10 m, and such a gravity- driven system can be easily implemented in households. A flat sheet membrane module with a membrane surface of 0.0016 m2 was operated in dead-end mode without any cross flow or backflushing.

For the experiments we used natural water from the Chriesbach river (Dübendorf, Switzerland) with the following composition: Turbidity 0.2-1 NTU with peak values of 30 NTU, and TOC 2-4 ppm. The membrane module was operated at a transmembrane pressure of 110 mbar. The flux decreased within the first 2

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days of filtration from 120 to 7-10 L/hm2 and remained stable for the studied period of 76 days independently on fluctuations of feed water quality. Upon variations of the pressure, the flux varied temporarily, but afterwards stabilized again to a value around 7-10 L/hm2. This implies that the permeability decreases with increasing pressures. Sodium azide (1.5%) was added to the feed in order to suppress biological activity without changing the NOM composition. The results show that the initial flux decline was similar to the first experiment, but no flux stabilization was observed and the flux continuously declined. From these results it can be concluded that biological activity has an important influence on the flux stabilization. Therefore, microbiological parameters were studied more in detail. The bioactivity in the feed and on the membrane was measured using the ATP method. The results show that the bioactivity on the membrane increases within the first 2 days and then stabilizes. The ATP material balance shows that during time the proportion of active cells on the membrane decreases, indicating cell die-off in the depth of the fouling layer. In the presence of sodium azide, biological activity (ATP) on the membrane was much lower. In the absence of sodium azide, the concentration of assimilable organic carbon (AOC) was determined in the feed water and it was observed that AOC correlates with the activity on the membrane (ATP). Considering that during time increasing amounts of suspended material from the feed water are deposited on the membrane, the stabilizing flux implies that the specific resistance of the fouling layer (m/m2) decreases. Based on the results, we postulate that this is based on biologically induced cell die-off, resulting in cavity formation and increased porosity.

More detailed results which support these mechanisms will be presented.

In contrast to conventional membrane plants, neither the membrane surface nor the capacity is a limiting factor for application of POU systems. While the required productivity of POU system is approx. 20-50 L/day, and assuming the flux of 7-10 L/hm2 the required membrane surface to provide the required capacity is 0.12-0.21 m2. Assuming a membrane price of 40 US$/m2, this corresponds to US$ 4.8-8.4 of membrane costs per POU system. Thus, in case the membrane life time is several years, the membrane costs are not prohibitive for application in developing and transition countries. Moreover, the system can be operated without pumps under hydrostatic pressure of 40 mbar or less, without regular backflushing, any addition of chemicals or multi-stage pretreatment.

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Drinking and Wastewater Applications V – 2

Friday July 18, 3:00 PM-3:30 PM, Maui

Treatment Performance and Detoxification of Coke Plant Wastewater Using an Anaerobic-Anoxic-Oxic Membrane Bioreactor System

W. Zhao (Speaker), Div. of Water Environment, Dept, of Environmental Science and Engineering, China - [email protected] X. Huang, Div. of Water Environment, Dept, of Environmental Science and Engineering, China D. Lee, Chemical Engineering Department, National Taiwan University, Taiwan M. He, Div. of Water Environment, Dept, of Environmental Science and Engineering, China

Coke plant wastewater is a kind of complex industrial wastewater generated in the iron and steel industry during coal carbonization and fuel classification. Its quantity and quality may vary fairly widely, depending on coal quality, coking temperature, and by-product recovery processes. The major contaminants in a typical coke plant wastewater consist of high concentration ammonia, toxic substances (such as cyanide, thiocyanate, phenols), and biologically inhibitory organic compounds. The conventional activated sludge process is usually not potent enough for removal and detoxification of these pollutants. Due to increasingly stringent regulations for receiving water bodies and industrial wastewater reuse strategies, achieving effective and safe control of this kind of wastewater is imperative. In this study, an anaerobic-anoxic-oxic membrane bioreactor (MBR) system was proposed to treat coke plant wastewater. Treatment performance at different hydraulic retention times (HRTs) was investigated. Acute toxicity test was applied to evaluate the toxicity change during the MBR system, and transformation of organic pollutants in the system was also analyzed.

The MBR system consisted of an anaerobic reactor (A1), an anoxic reactor (A2) and an oxic reactor (O) with a submerged hollow fibre polythene membrane (nominal pore size: 0.4 μm, membrane area: 0.2 m2, Mitsubishi, Japan). The anaerobic reactor was packed with soft media. The anoxic and oxic reactors were completely mixed tanks, and the mixed liquor recirculation was from the oxic one to the anoxic one. Compared conventional anaerobic-anoxic-oxic activated (CAS) system was operated at the same condition with MBR system. Raw coke plant wastewater was collected from Beijing Steel Company. Acute toxicity of wastewater was assessed by luminescent bacteria growth inhibition test, using Zn2+ as the toxicity reference substance. Transformation of organic pollutants in the system was analyzed by fluorescence excitation- emission matrix (EEM). The MBR process was operated in a constant mode. When the transmembrane pressure (TMP) reached around 0.3MPa, off line physical (with tap water) and chemical (with HCl, NaOH, NaClO) cleaning of the membrane

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was performed to restore membrane flux and then reinstalled in the aeration tank for continuous operation.

The MBR system was continuously operated for more than 500 days, employing different HRTs. The optimal conditions were obtained when the HRT of anaerobic, anoxic, and oxic reactors were 6.7, 13.3, and 20.0 h, respectively, with constant flux of 4.5L/(m2.h), an intermittent suction of membrane with 8 min on/ 2 min off, and recirculation ratio at 3:1. The MBR effluent average COD, NH3-N, TN concentrations and turbidity were 248±32 mg/L, 0.2±0.1 mg/L, 120± 11 mg/L, and 1.1±0.2 NTU with removal efficiencies of 90.2±1.0%, 99.9±0.1%, 74.4± 1.1%, and 99.6±0.1%. The effluent of the MBR system was free of suspended solids, and COD concentrations were lower than those from the CAS system, especially at high COD loading rates. In terms of removing NH3-N and TN, both MBR and CAS systems showed effective and no significant difference in ammonia loading rate from 0.08 to 0.22 kg NH3-N/(m3.d) and TN loading from 0.12 to 0.31 kg TN/(m3.d).

Acute toxicity test indicated that coke plant wastewater was highly toxic and 79.4±0.4% luminescent bacteria growth inhibition was observed even in 10 times dilution of raw wastewater compared with control solution, equal to toxicity of 9.60±0.12 mg/L Zn2+. Acute toxicity of wastewater decreased substantially through treatment of MBR system, with the effluent toxicity of 34.2±0.9% growth inhibition, equal to 0.19±0.01 mg/L Zn2+.

The contour maps of EEMs of the MBR influent and effluent revealed that two fluorophores of the influent with Ex/Em of 220-230/275-325 nm and Ex/Em of 250-280/275-325 nm were ascribed to phenols which were presumedly responsible for high toxicity of the raw coke plant wastewater. The other two fluorophores with Ex/Em of 220- 240/330-425 nm and Ex/Em of 250-290/330-425 nm were much alike with the effluent. These peaks may be associated with humic acid and fulvic acid, potentially refractory organic matters remained in coke plant wastewater.

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Drinking and Wastewater Applications V – 3

Friday July 18, 3:30 PM-4:00 PM, Maui

Time Course of Sub-Micron Organic Matter in MBRs: Relation to Membrane Fouling in MBRs

K. Kimura (Speaker), Hokkaido University, Sapporo, Japan - [email protected] N. Yamato, Hokkaido University, Sapporo, Japan T. Miyoshi, Hokkaido University, Sapporo, Japan T. Naruse, Hokkaido University, Sapporo, Japan Y. Watanabe, Hokkaido University, Sapporo, Japan

Membrane fouling in MBRs is still a big obstacle for widespread use of MBRs. In many previous researches, carbohydrates and/or proteins produced by microorganism during their metabolic activities were pointed out as the major foulants in MBRs. In this study, sub-micron carbohydrates and proteins in MBRs were investigated in relation to the evolution of membrane fouling.

Three pilot-scale MBRs equipped with PVDF hollow-fiber MF membranes (Mitsubishi Rayon Engineering, Tokyo, Japan) were installed at a municipal wastewater treatment plant and fed with real municipal wastewater. Nominal pore size of the membrane used was 0.4 µm. The three MBRs were operated with the identical membrane flux (i.e., 25 LMH) and with different SRTs of 16, 65 and 117 days. Concentrations of carbohydrates and proteins in the three MBRs were continuously and intensively monitored. Continuous operation of the three MBRs was carried out for 120 days after acclimatization of biomass. Three size fractions of organic matter (i.e., <0.1 µm, 0.1- 0.45µm and 0.45-1.0 µm) were considered in this study whereas only one dissolved fraction of organic matter (e.g., <0.45 µm) was considered in most of previous studies. Fouling is clearly divided into two types in this study: physically reversible fouling and physically irreversible fouling. Physically reversible fouling was defined as the fouling that can be cancelled by physical cleaning (e.g., backwashing) whereas physically irreversible fouling needs chemical membrane cleaning to be cancelled.

Increase in trans-membrane pressure (TMP) was very rapid in the MBR operated with SRT of 16 days. In the other two MBRs, increase in TMP was moderate. Increase in TMP in the MBR operated with SRT of 117 days was slightly faster than that seen in the MBR operated with SRT of 65 days.

Time course of organic matter (carbohydrates and proteins) with the size of 0.45-1.0 µm clearly synchronized the evolution of physically reversible fouling in the MBRs operated with the SRTs of 16 and 117 days: when physically reversible fouling became significant in the two MBRs, concentration of organic matter with the size of 0.45-1.0 µm synchronously increased. Regarding the MBR operated

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with the SRT of 65 days, no correlation between fouling trend and any fractions of organic matter was seen although physically reversible fouling became significant at the end of the continuous operation. Physically reversible fouling in the MBR with the SRT of 65 days was presumably explained by development of biofilms on the surface of membranes.

The rate of evolution of physically irreversible fouling significantly changed in the MBR operated with SRT of 16 days while those in the other two MBRs were relatively constant throughout the 140 days operation. It was suggested that time course of carbohydrates with the size of <0.1 µm synchronized the evolution of physically irreversible fouling. Those small carbohydrates could migrate into the micropores of the membrane used (i.e., 0.4 µm) and caused physically irreversible fouling.

Monitoring of one lumped and dissolved fraction of organic matter that was carried out in most previous researches seems to be insufficient to understand fouling phenomena in MBRs treating municipal wastewater. Division of the organic matter into several fractions would provide us with many useful insights. Also, analytical methods for monitoring of carbohydrates/protein might need to be upgraded. The phenol- sulfuric acid method that had been widely used in previous researches was used for determination of concentrations of carbohydrates in this study and the above- mentioned discussion was made on the basis of the concentration determined by the phenol-sulfuric acid method. In this study, analysis of carbohydrates in the MBRs with high-performance anion- exchange chromatography with pulsed amperometric detection (DIONEX) was additionally carried out after hydrolyzation of the samples. By this analysis, monosaccharides could be specifically detected. Increases in several monosaccharides (e.g., galactose or arabinose) in the MBR with SRT of 117 days were well correlated to the evolution of physically irreversible fouling in the reactor although concentration of carbohydrates determined by the phenol-sulfuric acid method did not show any correlations with the fouling trend of the reactor. One possible explanation for this is that the phenol-sulfuric acid method detected components that were not truly carbohydrates. Wastewater treatment processes inevitably involves a variety of components. In such a heterogeneous condition, monitoring of carbohydrates/proteins that cause membrane fouling might not be achieved by conventional analytical methods.

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Drinking and Wastewater Applications V – 4

Friday July 18, 4:00 PM-4:30 PM, Maui

On the Lookout for a Fouling Indicator – A Critical Evaluation of Various Methods for Fouling Characterization in MBR

A. Drews (Speaker), TU Berlin, Berlin, Germany - [email protected] T. de la Torre, Berlin Centre of Competence for Water, Berlin, Germany V. Iversen, TU Berlin, Berlin, Germany J. Schaller, TU Berlin, Berlin, Germany J. Stüber, Berlin Centre of Competence for Water, Berlin, Germany F. Meng, TU Berlin, Berlin, Germany B. Lesjean, Berlin Centre of Competence for Water, Berlin, Germany M. Kraume, TU Berlin, Berlin, Germany

Objectives Fouling still is a major issue in membrane research in general and in MBR research in particular. A multitude of manuscripts on fouling are constantly submitted. Despite all this effort, neither the culprit components nor the exact mechanisms are known and results are even contradictory to some extent. The main reasons for this are: 1) A wide variety of experimental, sample preparation but also evaluation methods are used in different groups. E.g., critical flux in its strictest form is agreed to be unattainable [1], so identification of the onset of the so-called critical flux is rather arbitrary. 2) Due to the complexity of the systems, researchers jumped to conclusions on observing any correlations at all. In the light of this it is not surprising that plenty of different fouling indicators are in use. The aim of this paper is not to add just another study on fouling but to step back and evaluate ‘traditional’ and new characterisation methods. Using a large variety of characterisation tools in a standardised way to monitor a number of different plants over several months, a pool of data was gained that will lead to more generally valid information on a) suited characterisation methods and b) suited data evaluation methods and ‘ hopefully ‘ c) culprit fouling components.

Methods Fouling propensity and mixed liquor characteristics were monitored regularly in 6 MBR plants (10 L to 250 p.e.) over a period of several months. In total, 10 chemical and physical mixed liquor characterisation methods were applied (polysaccharides and proteins in EPS and SMP [2, 3], CST, TTF, biopolymers via LC/OCD), including the novel TEP (transparent exopolymer particles) method [4] which yields information on a hitherto undetected fraction of polymers, and 2 different filtration test cells (ex situ sidestream and a novel in situ immersed). In the filtration experiments which were carried out to assess the individual fouling propensity of different sludges in a comparative manner, 3 different critical flux protocols and 2 data evaluation methods were compared (average TMP during each step and dTMP/dt [1]). This campaign is supplemented by data gained with the DfCm method [5].

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Results Critical flux measurements with sludges from 4 different plants showed that critical flux varies over time but is surprisingly similar in the investigated plants despite the fact that that chemical parameters like SMP and EPS differ by more than 100%. The different evaluation methods yielded variations within the range of normal change in feed behaviour (±20%). Due to the elimination of unfed and unaerated feed transport from MBR to filtration test rig, in situ filtration tests were thought to be superior [6]. Of the three protocols used, two gave a similar outcome while the result of protocol I (without relaxation between flux steps) was completely different. This shows the importance of standardising critical flux protocols for comparison of data. On cross-evaluating several results of chemical and physical analyses, no clear relationships could be observed. CST as a first tentative measure of filterability only gave a correlation with TEP concentrations [4]. While all other alleged chemical indicators vary quite a lot, critical flux remains pretty stable (see above).

Conclusions The applied large variety of fouling characterisation methods based on both physical and chemical analyses of the mixed liquor and supernatant over several months of operation of various plants will allow a more generally valid conclusion on the practical use of different assessment methods. Comparative short-term filtration tests like critical flux trials were further improved by an in situ set-up that eliminates unfed and unaerated sample storage. The applicability of the novel TEP method has been shown. So far, ‘traditional’ indicators like SMP and EPS gave no clear correlation with filterability. At the conference, more data of the ongoing campaign will be presented and cross-evaluated.

Acknowledgements Parts of this study were funded by the European Commission (AMEDEUS, REMOVALS, ENREM, MBR-TRAIN). Mr. Meng acknowledges the financial support through the Alexander von Humboldt-Stiftung. The authors wish to thank Renata Mehrez, Adrien Moreau, Moritz Mottschall and Djihan Beuter for their work, and BWB, A3 and Microdyn-Nadir for support and free supply of membrane material.

References

[1] Le Clech P, Jefferson B, Chang IS, Judd SJ, J Membrane Sci 227, 2003, 81-93.

[2] Dubois M, Gilles KA, Hamilton JK, Rebers PA, Smith F, Anal Chemistry 28, 1956, 350-356.

[3] Frolund B, Palmgren R, Keiding K, Nielsen PH, Water Res, 1996, 1749-1758.

[4] De la Torre T, Lesjean B, Drews A, Kraume M, Talanta (submitted).

[5] Evenblij H, Geilvoet S, van der Graaf JHJM, van der Roest HF, Desal 178, 2005, 115-124.

[6] Kraume M, Wedi D, Schaller J, Iversen V, Drews A, Desal (in press).

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Drinking and Wastewater Applications V – 5

Friday July 18, 4:30 PM-5:00 PM, Maui

Importance of Membrane Reactor Design for Membrane Performance in Biofilm-MBR

I. Ivanovic (Speaker), Norwegian University of Sci. and Tech., Trondheim, Norway - [email protected] T. Leiknes, Norwegian University of Sci. and Tech., Trondheim, Norway

A Biofilm-MBR is an alternative concept to activated sludge - MBR where a biofilm reactor is employed instead an activated sludge reactor, and where the membrane reactor is designed only as an enhanced particle separation unit. Possible advantages of this concept lie in the fact that biomass is attached to suspended carriers and there is no need for sludge (i.e. biomass) recirculation in the system. Additionally, only small amounts of biomass that become detached from biofilm carriers need to be separated in membrane reactor. [1]. A lower amount of suspended matter that needs to be separated gives less fouling potential with regard to cake formation on the membrane surface. However, submicron particles and colloidal organic matter remain significant foulants as reported in previous studies [2][3][4]. For this study a small-scale pilot plant was operated, consisting of moving-bed- biofilm reactor (working volume of 260 L), coupled with a submerged membrane reactor (MR) with Zenon ZW10 hollow fiber membrane modules (membrane area 0.93m2). Municipal wastewater was fed to the pilot plant and operated under low organic loading conditions, giving on average >90 % ammonium removal. The biofilm reactor was operated with a 4 hour hydraulic retention time. Suspended solids (SS) in the effluent from the biofilm reactor varied between 90 - 150 mg L-1, while COD and FCOD were between 120-242 and 25.9-43.1 mg O2 L-1 respectively. The membrane reactor was operated in a 5 minute cycle with production flux 35 LMH, backwash flux 42 LMH and recovery 96%. Continuous air scouring of the membrane was employed for all tests with specific aeration demand (SADm) set on approximately 1 Nm3airm-2membrane areah-1.

Three membrane reactor designs were compared: 1) a completely mixed reactor (CM-MR), 2) membrane reactor with integrated sludge pocket (SP-MR) and 3) a membrane reactor with a modified sludge pocket (MSP-MR). Volumes of the membrane reactors were 9, 25 and 41 L respectively. Preliminary results showing that design i.e. geometry of the membrane reactor play an important role in membrane performance. Steady state concentrations of MLSS around the membrane area were ~3900, ~1000, ~400 mg/L giving fouling rates within production cycle of 20, 6, and 3×10-5 bar sec-1, respectively. Lower concentrations of MLSS and COD around the membranes as a function of the modified rector designs results in a better membrane performance. Reduction in

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MLSS is not directly proportional to a reduction of fouling rates (i.e. dTMP/dt). The characteristics of suspended matter around the membrane play an important role in membrane fouling, however, a reduction in these foulants by an enhanced membrane reactor design is a significant contribution to controlling and minimizing fouling of the membrane. Soluble matter (i.e. FCOD) was reduced by ~ 40% in MSP- MR compared to CM-MR. Particle size distribution analyzed in membrane reactors showed that the differential number percentage of submicron particles around the membrane in the reactors with a sludge pocket design (SP-MR and MSP-MR) could be reduced by ~ 8 % and ~ 10 % respectively, compared to a completely mixed design membrane reactor (CM-MR).

In the presentation will be given more in detail design characteristics of compared reactors and analyzed their effects on membrane performance i.e. membrane fouling.

References.

[1] Leiknes T.O. and Ødegaard H., (2007) The development of a biofilm membrane bioreactor , Desalination, 202:135-143

[2] Leiknes, T.O.; Ivanovic I.; Ødegaard H,(2006) Investigating the effect of colloids on the performance of a bio�lm membrane reactor (BF- MBR) for treatment of municipal wastewater. Water S.A.

[3] Ivanovic I; Leiknes T.O.; Ødegaard H., (2006) Influence of loading rates on production and characteristics of retentate from a biofilm membrane bioreactor (BF-MBR). Desalination ;199:490-492

[4] Ivanovic I; Leiknes T.O.; (2008) Impact of aeration rates on particle colloidal fraction in the biofilm membrane bioreactor (BF-MBR). In Press, Desalination

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Fuel Cells III – 1 – Keynote

Friday July 18, 2:15 PM-3:00 PM, Moloka’i

Crystalline Order and Membrane Properties in Perfluorosulfonate Ionomers for PEMFC Applications

R. Moore (Speaker), Virginia Tech, Blacksburg, Virginia, USA - [email protected]

In this study, we explore the form and function of the crystalline domains in perfluorosulfonate ionomer membranes. This fundamental project is aimed at filling a critical void in our understanding of the form and function of polymeric crystals produced by the ordered packing of backbone chains in modern fuel cell membranes. While we have learned a great deal about the organization of the proton-conducting ionic domains in functional polymers such as the perfluorosulfonate ionomer (PFSI) Nafion, it is remarkable that we know very little about the detailed structure and formation of the crystallites in these materials or the spatial arrangement of these ordered features with respect to the proximity of the ionic domains. In contrast to the vast majority of morphological studies of these technologically important polymers, this project will be focused on the ‘other’ important morphological feature in these membranes, namely the critical significance of the crystalline component.

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Fuel Cells III – 2

Friday July 18, 3:00 PM-3:30 PM, Moloka’i

Model Studies of the Characterization of the Durability of Nafion® Membranes and Nafion/Inorganic Oxide Nanocomposite Membranes

K. Mauritz (Speaker), University of Southern Mississippi, Hattiesburg, Mississippi - [email protected] M. Hassan, University of Southern Mississippi, Hattiesburg, Mississippi Y. Patil, University of Southern Mississippi, Hattiesburg, Mississippi D. Rhoades, University of Southern Mississippi, Hattiesburg, Mississippi

Selected results from the investigation of the degradation of Nafion perfluorosulfonic acid membranes in the fuel cell environment will be presented. The topics will include a detailed explanation of the use of the powerful technique of modern broadband dielectric spectroscopy which can interrogate macromolecular motions as well as charge motions over a vast range of time and distance scales. Long range main chain motions associated with the glass transition (² relaxation) as well as a higher temperature transition involving the disruption of polar associations (± relaxation) are revealed. The shift in chain dynamics of Nafion as seen through real-time in-cell dehydration, as well as post-chemical degradation will be discussed. It will also be explained how the distribution of relaxation times is related to the shift in Nafion molecular weight distribution with degradation by radicals issuing from peroxide decomposition. Finally, the concept and rationale for the use of Nafion membranes that are inorganically modified with membrane - in situ - synthesized sol-gel-derived nanoscopic fillers, including a possible benefit of mitigating mechanical degradation, will be presented. Viscoelastic relaxation studies of alteration of mechanical properties through these inorganic modifications will be discussed.

Acknowledgments:

Funding for this work was provided by DuPont Fuel Cells and DOE Office of Energy Efficiency and Renewable Energy; contract # DE-FC36-03GO13100 and DE-FG36-06GO86065.

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Fuel Cells III – 3

Friday July 18, 3:30 PM-4:00 PM, Moloka’i

PBI Polymers for High Temperature PEM Fuel Cells

B. Benicewicz (Speaker), University of South Carolina, USA - [email protected]

Polybenzimidazole (PBI) polymers are excellent candidates for PEM fuel cell membranes capable of operating at temperatures up to 200°C. The ability to operate at high temperatures provides benefits such as faster electrode kinetics and greater tolerance to impurities in the fuel stream. In addition, PBI membranes doped with phosphoric acid can operate efficiently without the need for external humidification and the related engineering hardware to monitor and control the hydration levels in the membrane. PBI membranes are currently being investigated as candidates for portable, stationary, and transportation PEM fuel cell applications. A new sol-gel process was developed to produce PBI membranes loaded with high levels of phosphoric acid. This process, termed the PPA process, uses polyphosphoric acid as the condensing agent for the polymerization and the membrane casting solvent. After casting, absorption of water from the atmosphere causes hydrolysis of the polyphosphoric acid to phosphoric acid. The change in the nature of the solvent induces a sol-gel transition that produces membranes with high loadings of phosphoric acid and a desirable suite of physical and mechanical properties. The new membranes were characterized through measurements of acid doping levels, ionic conductivity, mechanical properties and fuel cell testing. The durability of these new membranes in multiple operating environments is of particular importance for the further development of practical fuel cell devices. Testing protocols have been developed to examine the behavior of PBI membranes under both static and cyclic conditions. The results of long-term testing under these conditions as well as long term static testing will be presented.

The development of the PBI membranes has also led to major advances in hydrogen separation, purification, pumping, and compression technologies. Recent developments in polybenzimidazole (PBI) proton conducting membranes have been applied to electrochemical hydrogen pumping. The basic properties of these membranes as high temperature (>100°C) proton conductors, combined with the well-known chemical stability, high tolerance to gas impurities, and potential for low cost, provide the significant advancement in this enabling technology for hydrogen purification. In this presentation, we will outline the basic technology associated with this device and describe the applications of these devices in both the future hydrogen economy and current industrial hydrogen gas user markets.

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Fuel Cells III – 4

Friday July 18, 4:00 PM-4:30 PM, Moloka’i

Novel Electrolytes for Fuel Cell Electrodes

J. Muldoon (Speaker), Toyota Motor Engineering & Manufacturing North America, Inc., Ann Arbor, Michigan, USA - [email protected] R. Wycisk, Case Western Reserve University, Cleveland, Ohio, USA J. Lin, Case Western Reserve University, Cleveland, Ohio, USA P. Pintauro, Case Western Reserve University, Cleveland, Ohio, USA K. Hase, Toyota Motor Corporation, Japan

Fuel cells (FC) are attracting great attention due to their high energy conversion efficiency and low pollution emission, relative to conventional combustion engines. Among various types, proton exchange membrane fuel cells (PEMFC) have emerged as promising power generators for portable, stationary, and automotive applications. For hydrogen/air and direct methanol fuel cells, a typical electrode binder is a perfluorsulfonic acid polymer such as Nafion" (DuPont) which shows exceptional chemical stability, good mechanical strength, high proton conductivity, and high gas permeability (oxygen/hydrogen). Unfortunately, Nafion" is very expensive and poses a serious environmental threat of HF release upon its decomposition under FC operating conditions and during recycling of the catalyst, which would be avoided if a non-fluorinated polymer were used. Polyphosphazenes are an attractive class of polymers with a backbone composed of alternating phosphorus and nitrogen atoms. Through appropriate functionalization of the backbone, the properties of these polymers can be designed to an extent unachievable with other types of materials. Here we report on the preparation and fuel cell performance of catalyst inks containing sulfonated polyphosphazenes. The method of preparing membrane-electrode-assemblies with polyphosphazene-based binders will be described and the resulting hydrogen/air fuel cell performance plots will be contrasted to those obtained with Nafion as the electrode binder.

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Fuel Cells III – 5

Friday July 18, 4:30 PM-5:00 PM, Moloka’i

Effect of Hydrocarbon Ionomer on Electrochemical Performance of MEA for Direct Methanol Fuel Cell (DMFC)

S. Lee (Speaker), School of Chemical Engineering, Hanyang University, Korea C. Lee, School of Chemical Engineering, Hanyang University, Korea Y. Lee, School of Chemical Engineering, Hanyang University, Korea - [email protected]

Direct methanol fuel cells (DMFCs) have been receiving much attention as clean and alternative energy source owing to high energy efficiency and excellent power density. The fuel cell performances are significantly affected by electrochemical properties of membrane-electrode assemblies (MEAs) where the electrochemical reactions take a place at the three-phase boundary zone consisting of catalyst, catalyst binder and proton exchange membrane (PEM). Hear, a catalyst binder acts as proton conductor as well as a mechanical supporter in the catalyst layer. The binder also contributes to enhanced dispersion of catalyst. A high-performance electrode requires good adhesion between the membrane and electrode, uniform catalyst dispersion in the electrode and good ion conduction. These properties are influenced by the component materials and fabrication process of the electrode. In most cases, Nafion® ionomer (EW=1,100) has been used as catalyst binder, irrespective of membrane materials. A severe delamination in MEAs occurred between low-cost hydrocarbon membrane and Nafion® ionomer owing to incompatibility between a catalyst binder and a membrane material. MEA containing hydrocarbon membrane needs a new hydrocarbon catalyst binder to reduce interfacial resistance with catalyst layers. Unfortunately,only a little attention has been paid so far to the catalyst binder compatible with the alternative electrolyte membranes. In this study, a new type of hydrocarbon binder (B1) was designed to fabricate a desirable MEA based on sulfonated polymer membrane. The effects of B1 binder on MEA properties and also on its electrochemical cell performance are investigated.

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Ultra- and Microfiltration III - Membranes – 1 – Keynote

Friday July 18, 2:15 PM-3:00 PM, Honolulu/Kahuku

Pilot-scale Integrity Monitoring of Microfiltration Processes Using a Novel Multi-membrane Sensor

F. Wong (Speaker), Advanced Water and Membrane Centre, Institute of Env. Sci. and Eng., Singapore - [email protected] A. Fane, Nanyang Technological University, Singapore J. Phattanarawik, Norwegian University of Sci. and Tech., Norway M. Wai, Advanced Water and Membrane Centre, Institute of Env. Sci. and Eng., Singapore J. Su, Advanced Water and Membrane Centre, Institute of Env. Sci. and Eng., Singapore

Effective contaminant removal in a membrane process is guaranteed only when the membrane is intact. In practice, the performances of the membrane filters may be compromised by presence of oversized pores, broken fibres or leaking O- ring connectors. Membrane integrity monitoring is to verify whether membrane filters are meeting the treatment objectives. The popular methods used for membrane integrity monitoring are pressure decay test, particle counting and particle monitoring, sonic testing, and turbidity measurement [1-3]. Unfortunately, the currently available integrity monitoring techniques show some disadvantages, i.e. labour- intensive, time-consuming, high cost, low sensitivity or requiring highly skilled operator, which limit their application.

The work presented here is part of an on-going project on pilot-scale integrity monitoring of filtration processes. Novel membrane integrity sensors developed by Phattaranawik et al. were employed in the pilot trials [4]. The novel sensor is a two-membrane device incorporating small-area membranes connected in series. The permeate from the first membrane flows totally to the second membrane, considered to be the retentate of the second membrane. Sensor parameter is defined as the ratio of the trans- membrane pressures of the two membranes. When there is the problem such as a breach, chemical degradation or biological degradation of the filtration membrane or mechanical failure of O- rings or gaskets, more particles in the filtrate will deposit on the surface of the first membrane within the sensor, resulting in significant drop in the permeate pressure of the first membrane. Consequently, increased trans- membrane pressure of the first membrane and decreased trans-membrane pressure of the second membrane are observed. The value of sensor parameter thus rises, and an alarm will be sent to the operator if the sensor parameter exceeds certain limit. Pilot testing of the integrity sensor would be performed at three different water plants in Singapore. The source waters used would be MF treated secondary effluent (plant 1), submerged membrane treated reservoir water (plant 2), and MBR treated municipal wastewater (plant 3). Several integrity sensors would be installed at the three sites and the continuous online integrity testing would last for several months.

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Some preliminary results were obtained from the sensors installed at plant 1. Using Millipore® membranes with pore size of 0.45μm, two sensors operated at average filtrate pressures of 1.05 and 0.49 bar (gauge) gave average sensor parameters of 0.79 and 0.24, respectively. It was observed that the values of sensor parameter did not deviate too much from the average value at the higher filtrate pressure whilst the values of sensor parameter were more dispersed at the lower filtrate pressure. This may elucidate the sensitivity of sensor parameter subjected to the fluctuation in filtrate pressure. The average values of sensor parameter for these two sensors were constant and stable during the period of observation, indicating that the microfiltration membranes were intact. One sensor equipped with Millipore® membranes with pore size of 0.22μm gave an average sensor parameter of 0.62 at an average filtrate pressure of 0.68 bar (gauge). Slight decrease in the permeate pressure of the first membrane within this sensor was observed. As a result, the value of sensor parameter increased a little. This is an indication of increasing amount of particles in the MF treated secondary effluent. The online monitoring is to be continued and further observation would help to confirm whether MF membrane is still intact or not. The installation work of the sensors is being carried out at plants 2 and 3, and part of the results from the pilot trails would also be reported in due time.

References

G.F. Crozes, S. Sethi, B.X. Mi, J. Curl, B. Marinas. Improving membrane integrity monitoring indirect methods to reduce plant downtime and increase microbial removal credit. Desalination 149 (2002) 493-497.

K. Glucina, Z. Do-Quang, J.M. Laine. Assessment of a particle counting method for hollow fiber membrane integrity. Desalination 113 (1997) 183- 187. K. Farahbakhsh, D.W. Smith. Estimating air diffusion contribution to pressure decay during membrane integrity tests Journal of Membrane Science 237 (2004) 203-212.

J. Phattanarawik, A.G. Fane and F.S. Wong (2006). US Provisional Patent, ETPL Pat Ref: SRC/p/04267/00/US, Filing date: 10 May 2006.

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Ultra- and Microfiltration III - Membranes – 2

Friday July 18, 3:00 PM-3:30 PM, Honolulu/Kahuku

Integrity Monitoring for Membrane Bioreactor Systems through Turbidity and SDI Measurement

F. Zha (Speaker), Siemens Water Techologies, South Windsor, Australia V. Kippax, Siemens Water Technologies, South Windsor, Australia - [email protected] R. Phelps, Siemens Water Technologies, South Windsor, Australia T. Nguyen, Siemens Water Technologies, South Windsor, Australia

Integrity of a membrane filtration system plays a critical role in the overall permeate quality of the system. The water treatment industry has developed methods to test membrane filter integrity, both direct and indirect. Direct methods of integrity testing measure a breach in the membrane surface, such as diffusive airflow and pressure decay (PDT) tests. Whereas, indirect methods of integrity monitoring measure the resulting permeate from the membrane system, including turbidity measurement, slit density index (SDI) and challenge tests.

The main index used to correlate the test methods to water quality is the log reduction valve (LRV = Log(Cinf/Ceff). The PDT method has been widely used in measuring the integrity of membrane system and results can be correlated with the permeate quality, LRV.

It has traditionally been recommended to use the PDT method for integrity monitoring for membrane bioreactor (MBR) systems; however, the suspended solids (SS) concentration is many times higher than the feed water of other membrane systems. This paper seek to investigate methods of integrity testing and through the information presented demonstrate that turbidity measurement and slit density index for RO pre-treatment is sensitive enough to monitor the integrity of MBR systems and traditional direct methods may not accurately predict the permeate quality.

Relationship between turbidity and MLSS concentration

Samples taken from activated sludge tanks were diluted to different suspended solids concentrations and the turbidity was measured. The results demonstrate that turbidity can be directly related to the MLSS concentration, with the bio-mass sources having little influence; aerobic, anoxic or membrane tank. The relationship of turbidity and MLSS concentration can be correlated as Turbidity (NTU) = 0.916 [MLSS (mg/L)]0.968 (1)

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MBR systems typically operate with a MLSS concentration ranging between 5,000 to 30,000 mg/L, a turbidity range of 3,500 to 20,000 NTU (eqn. 1). Membrane directly filters such mixed liquor and produce clean permeate with a turbidity of around 0.1 NTU, achieving LRV>4.5. The resolution of standard turbidimeter is about 0.01 NTU, therefore with the meter it is easy to measure LRV of 5.

Integrity monitoring in MBR

An integral membrane module consisting of 2000 fibers was used in MBR to filter mixed liquor with a SS of 12,500 mg/L. The baseline turbidity was recorded as 0.06 NTU. Then 1, 2 and 5 fibers were cut respectively at the top end. The results of this test are shown in the table below. From the PDT results, poor permeate turbidity and fecal coliform results were expected. However, on-line turbidity meter recording shows an initial surge in turbidity, but turbidity of permeate rapidly dropped back to less than 0.2 NTU.

Number of cut fibers at top end 1 2 5 Loss of pressure in PDT (kPa/min) 30 60 ~120 Peak turbidity(NTU) 1.993 1.349 2.4 Average turbidity 24h (NTU) 0.136 0.147 0.196 Fecal coliforms in permeate(cfu/100 mL) <1 <1 5

MBR pilot experiments show that the PDT method can test the integrity of the membrane system, but fails to predict the permeate quality from MBR. The extremely high suspended solids concentrations seen with the MBR system quickly plugs any broken fibers.

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Ultra- and Microfiltration III - Membranes – 3

Friday July 18, 3:30 PM-4:00 PM, Honolulu/Kahuku

Membrane Characterisation : Assessment of the Bacterial Removal Efficiency

N. LeBleu (Speaker), Université de Toulouse, Toulouse, France C. Causserand, Université de Toulouse, Toulouse, France C. Roques, Université de Toulouse, Toulouse, France P. Aimar, Université de Toulouse, Toulouse, France - [email protected]

The retention of microorganisms is one of the praised advantages of filtration membranes used for bioprocesses, or water and waste water treatments. Nevertheless, the removal efficiency of membranes or modules may be reduced by the presence of a small number of abnormally large pores. The qualification of such membranes, and the question of their integrity, which can be carried out by various types of testing methods, have to be relevant and sensitive. However several works show that membrane characterisation and integrity monitoring based on tracers rejection and air tests are not sensitive enough to detect such imperfections [1-3]. They provide at best information on defects larger than 3 µm [4]. As a consequence, they are not adapted to predict the removal efficiency for smaller microorganisms such as bacteria [5].

In this context, we have worked on a new approach for membrane characterization, based on the specific behaviour of bacteria during filtration that we revealed in a former experimental study [6]. It appears that the bacterial transport through a porous membrane structure can be assisted by its deformation and this phenomenon is governed by the structural characteristics of the cell wall, namely the peptidoglycan layer. The more this layer is thin and elastic, the more the bacteria will deform, and will likely pass through pores smaller than its own size. As a consequence, rejection mechanisms based on steric effects are inadequate to assess the membrane rejection capacity since bacteria of equal size can exhibit different behaviours in filtration depending on their deformability. The present study is divided in two parts : the description of the characterisation methodology and its application to commercial membranes.

Challenge tests were performed on flat-sheet polycarbonate track-etched microfiltration membranes of different nominal pore sizes (0.05 - 0.2 - 0.4 - 0.8 - 1.2 µm). This type of membrane was chosen as model due to their well-defined pore geometry which allows breaking the bacterial transfer into elementary mechanisms. For the following part of the study, we assume that the bacteria transport trough one these pores is equivalent to the one through a small defect or an abnormally large pore of an ultrafiltration membrane. Five bacterial strains of various morphological and structural characteristics were selected in function

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of the flexibility of their external membrane (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Brevundimonas diminuta and Micrococcus luteus). Dead-end filtration experiments, in a stirred filtration cell, were carried out with bacterial suspensions of each strain at 104 CFU/mL as feed solutions. Transmembrane pressure was set at 0.5 bar for all trials. Steadily, filtration flux was measured and permeate samples were collected. Viable bacteria were then enumerated after culture into solid nutrient agar medium (24 h at 37 °C).

According to the results of those trials, the assessment of the presence of bacteria in the permeates has allowed to associate each strain to one only of the homoporous membranes tested. The interesting feature is that there is not a direct correspondence between the size of the pores (homoporous membranes) and the size of the bacteria, and this because of the deformation of the latter during the filtration process. Moreover, since when several bacteria are present in a dispersion they do not exhibit the same rejection as when they are filtered one by one, successive filtrations of each bacterial suspension are ncessary to accurately assess the presence of the largest pores in the structure of a tested membrane and to evaluate the range of their diameter.

For instance, if an unknown membrane fully retains Escherichia coli, we can consider that defects of 0.4 µm in diameter are not enough numerous to alter the membrane removal capacity. If this tested membrane leaks Pseudomonas aeruginosa to some extent, one concludes that the presence of pores of at least 0.2 µm is not negligible. The application of this methodology to various commercial ultrafiltration membranes and to membranes with a controlled porosity will be presented.

To conclude, in complement to other characterisation tests, this methodology could be a well-adapted tool to qualify filtration membranes or modules in terms of bacterial removal efficiency and to carry out unbiased comparison between membranes in a benchmarking context.

References

[1] Causserand et al. 2002 - Desal vol.149 p.485.

[2] Shinde et al. 1999 - J Membr Sci vol.162, p.9.

[3] Kobayashi et al. 1998 - J Membr Sci vol.140 p.1.

[4] Farahbakhsh 2003 - JAWWA vol.95 p.95.

[5] Urase et al. 1996 - J Membr Sci vol.115, p.21.

[6] Delebecque et al. 2006 - Desal vol.199 p.81.

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Ultra- and Microfiltration III - Membranes – 4

Friday July 18, 4:00 PM-4:30 PM, Honolulu/Kahuku

Pore Size Determination of UF and MF Membranes By Streaming Potential Measurement

K. Nakamura (Speaker), Yokohama National University, Yokohama, Japan - [email protected] K. Matsumoto, Yokohama National University, Yokohama, Japan

The streaming potential of microporous membrane is used for characterization of charge properties of pore surface while the streaming potential can depend not only on surface charge of pore surface but also on ionic strength of solution and membrane pore size. In this study the pore size characterization method of MF/UF membranes based on the streaming potential measurement was developed. The pore size characterized by the streaming potential measurement was compared to AFM image or molecular weight cut off(M.W.C.O.), which was measured using polyethylene glycol( PEG). The membranes used were polysulfone UF membranes(M.W.C.O. 10k, 50k, 200k Da), aromatic polyamide UF membrane(M.W.C.O.20k Da) and polycarbonate MF membranes(nominal pore size 50, 100, 200 and 400nm). Potassium chloride solution was used as electrolyte. The electrical potential difference across the membrane was measured with Pt-black wire electrodes equipped to both sides of membrane. In all membranes measured the streaming potential showed minus value and increased with the increase in conductivity and approached to zero. The experimental curve was well simulated by the calculation result of space charge model except for lower conductivity region, which means the model is valid for higher ionic strength region. By this analysis the pore radius rp and surface charge density qp could be determined as fitting parameters. In order to confirm the relationship between rp and actual retention performance M.W.C.O. for UF membranes was measured with PEG. rp showed a good linear relation with Stokes diameter estimated from M.W.C.O. values. In polycarbonate microfiltration membranes rp showed a good linear relation with pore size determined by AFM image. These results showed that the rp determined by streaming potential measurements is useful for predict the separation performance of UF/MF membranes.

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Ultra- and Microfiltration III - Membranes – 5

Friday July 18, 4:30 PM-5:00 PM, Honolulu/Kahuku

Acoustic Investigation of Porous and Membrane Structures

S. Léoni, Ecole Centrale Marseille, Marseille, France J. Bonnet, Université Paul Cézanne Aix Marseille, Provence, France Y. Wyart (Speaker), Université Paul Cézanne Aix Marseille, Provence, France - [email protected] J. Allouche, Ecole Centrale Marseille, Marseille, France P. Moulin, Université Paul Cézanne Aix Marseille, Provence, France

The processes of membrane filtration are in the heart of actual and future environmental challenges. Nevertheless, in order to increase the impact of membrane separation techniques in industrial field, the phenomenon of membrane fouling must be more understood. The membrane fouling can be monitored by measuring the increase of transmembrane pressure when the filtration is made at a constant flow rate. This procedure is a good indicator to estimate the frequency of backwashes or chemical cleanings; but gives no information about the kinetic of the fouling phenomenon, the fouling location (on membrane surface or in the membrane bulk), the structure of the cake& Moreover, it is well known that the membrane fouling depends on the structural characteristics of the membrane. The aim of the study is to develop an acoustic method to characterize first new membranes and secondly fouled membranes. This method must be non- invasive to avoid the destructuration of the cake and simple for an easy use.

The present work deals with acoustic characterisation of porous media and membrane using impedance tube. This kind of materials is widely used throughout industry to measure the sound absorption coefficient and other acoustic properties of materials. Low frequency acoustic method is used to determine porosity from acoustic sample properties. The experimental setup is composed of a sound source, two microphones and a sample holder. The sound source (speaker), placed at an extremity of a rigid walled tube, generates incident plane waves which are partially reflected by the material sample, located at the other extremity of the tube (sample holder). The incident and reflected waves interfere and create a system of standing waves. For sufficiently low frequencies, it is a plane wave which is propagated along the tube axis. The lower limit frequency is dependent on the microphones limitation and on the spacing between microphones. The higher limit is given by the cut off frequency of the tube. Placed at the end of the tube, two microphones measure the acoustic pressure in order to calculate the frequency response function (FRF). This FRF is used to determine the complex acoustic surface impedance Z of the sample. The method presented in this paper is based on the theories of Lafarge- Allard which are based on a low frequency approximation. Using this assumption, porosity Phi

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can be deduced from the imaginary part of the surface impedance Z of the material according to the relation below:

Phi=(P0/we). Im(1/Z)

with, P0 the atmospheric pressure (Pa), w the angular frequency (rad.s-1) and e the sample thickness.

The porosity is obtained by an average over a selected optimal frequency interval where ¦ does not depend on the frequency. This acoustic method allows accessing other porous media properties such as permeability, tortuosity&

Experimental procedure and data treatment need to be validated and calibrated. For calibration, two products are used: cork and melamine. For porous media characterisation, two different porous materials were investigated and different results are obtained: open-celled metal foam and microfiltration plane membrane. These two kinds of materials are very different in the cell topology and the material made of, but exhibit similar porosity values ranged from 80 to 90%. Metals foams are used as reference material for experimental set up validation. Indeed, the geometrical parameters as well as the physicals properties (pore diameter, porosity, material, permeability&) of each studied metal foam sample were already finely characterized. In addition with the set up validation function, data obtained lead to an improved understanding of sound absorption in open-celled metal foams for noise control applications. With these results, we can investigated the filtration of particles generated from the combustion of different products (oil, fuel, municipal waste, biomass) more especially the the influence of the metallic foam thickness on the retention. In fact, we have observed that the particles flow is less and less important with the progression through volume of the metallic foam and the retention becomes less efficient.

Tests were carried out using microfltration plane membrane. As these membranes are very thin (0.1mm), a stack of several specimens layers are required to better capture the physical of the material. In order to evaluate the stack thickness impact on the determination of the membrane porosity, a first tests series was performed for length varying in the range 1mm to 5mm. A good agreement was obtained between our results and the porosity value given by the manufacturer.

A second tests series concerned the impact of new membranes and fouled membranes on the FRF; it is in progress and will be presented during ICOM 2008.

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Ultra- and Microfiltration III - Membranes – 6

Friday July 18, 5:00 PM-5:30 PM, Honolulu/Kahuku

Ellipsometric Observation of Ceramic Membranes

R. Tamime, Université Paul Cézanne Aix Marseille Y. Wyart (Speaker), Université Paul Cézanne Aix Marseille - [email protected] L. Siozade, Université Paul Cézanne Aix Marseille C. Deumié, Université Paul Cézanne Aix Marseille P. Moulin, Université Paul Cézanne Aix Marseille

The application of membrane processes in the industrial world is impeded by a major drawback: membrane fouling. During the filtration steps, this fouling can occur either on the surface or within the pores of the membrane. Where this fouling occurs not only affects the permeate flux and/or the selectivity but is also of crucial importance for the membrane regeneration step. The membrane fouling corresponds to an accumulation of matter which occurs either on the membrane surface or inside the porous matrix. The structural properties of membranes (roughness, porosity) have an impact on fouling phenomenon and must be characterized to develop a fouling control method.

In this work, the angle resolved scattering technique and the analysis of the scattered wave polarization state using the technique of Ellipsometry of Angle Resolved Scattering are used to characterize ultrafiltration and microfiltration membranes and discriminate between them. The main objective of this work is to show the potential of these recent optical techniques not well defined or used in the domain of membrane processes. The information, obtained for ceramic membranes, is compared for different cut-offs (300 kDa, 0.1 µm, 0.45 µm and the corresponding support). The measurements are made using an instrument called ‘scatterometer’ which allows angular measurements for discrete wavelengths ranging from UV (325 nm) to the mean IR (10.6 μm). Measurements at low angle resolution (sampling interval of a few degrees) or at high angle resolution (sampling interval of a few hundreds of degrees) can be performed. The experimental setup is composed of a photomultiplier and a synchronous detection apparatus. The beam is mechanically modulated (chopper). Part of the beam is deviated upstream (reference) and measured together with the rest of the beam to avoid the possible fluctuations of the light source power. The laser to be used is selected through a system of mirrors mounted on a translation plate. The optical signal is collected by a 1 mm diameter glass fiber that can move throughout the entire space along the usual angular directions.

First, the angle resolved scattering technique was performed at low and high resolution mode. For low resolution as well as for high resolution mode, it appeared difficult to extract one parameter allowing the differentiation of the

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membranes. The analysis of the light scattering intensity did not make it possible to separate the bulk states of these components. That is why the polarimetric behavior of each sample was studied. The analysis of the scattered wave polarization state at low resolution measurements clearly revealed that the origin of the light scattering lies essentially in the bulk. Indeed, the polarimetric phase shift varies very quickly, which is representative of bulk scattering. With low angle resolution, comparison of different membrane cut off is not significant. To analyze statistically the oscillations of the polarimetric phase shift as a function of the scattering angle, the same measurements were run at high angle resolution. By representing the standard deviation of the polarimetric phase shift, it is possible to identify a difference in membrane behavior. Logically, the phase shift standard deviation increases with the porosity. To confirm this result, some theoretical investigations were run. Simulations were performed using the differential method, which is a rigorous method for the resolution of Maxwell’s equations. The polarimetric phase shift of the wave scattered by a porous structure with a defined volumic structure (pore size and material) was calculated. The membranes were modeled by a volume 8 μm in width and 1 mm in depth, filled with a mixture of air (optical refraction index:1) and zircone (optical refraction index: 2.2, absorption neglected). In the case of membranes with porosities ranging from 20 to 400 nm, modelling step shows that the standard deviation increases with the sample porosity. These numerical calculations confirm the evolution observed for the experimental results.

The ellipsometry of angle resolved scattering can be used for the structural characterization of the organic membranes whatever the membrane geometry. The study of these membranes must allow to develop a methodology in order to improve the understanding of the fouling mechanisms, to correlate the membrane properties (membrane cut- off, membrane material) to the fouling and to minimize the membrane fouling.

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Membrane Contactors – 1 – Keynote

Friday July 18, 2:15 PM-3:00 PM, O’ahu/Waialua

Modelling Aroma Stripping Under Various Forms of Membrane Distillation Processes

G. Jonsson (Speaker), Technical University of Denmark, Lyngby, Denmark - [email protected]

Concentration of fruit juices by membrane distillation is an interesting process as it can be done at low temperature giving a gentle concentration process with little deterioration of the juices. Since the juices contains many different aroma compounds with a wide range of chemical properties such as volatility, activity coefficient and vapor pressure, it is important to know how these aroma compounds will eventually pass through the membrane.

Experiments have been made on an aroma model solution and on black currant juice in a lab scale membrane distillation set up which can be operated in various types of MD configurations: Vacuum Membrane Distillation, Sweeping Gas Membrane Distillation, Direct Contact Membrane Distillation and Osmotic Membrane Distillation. The influence of feed temperature and feed flow rate on the permeate flux and concentration factor for different types of aroma compounds have been measured for these MD configurations.

A general transport model for the flux of water and aroma compounds have been derived and compared with the experimental data. A reasonable agreement between the modelling and the experiments could be obtained. From the modelling it was possible to explain the large different in permeate flux and concentration factor that was observed for the different MD configurations. This is highly related to the heat and mass transfer resistances in the membrane as well as in the boundary layers adjacent to the membrane surface and how the driving force develops along the length of the membrane.

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Membrane Contactors – 2

Friday July 18, 3:00 PM-3:30 PM, O’ahu/Waialua

Membrane Extraction for Acetic Acid and Lignin Removal from Biomass Hydrolysates

D. Grzenia, Colorado State University, Fort Collins, Colorado, USA D. Schell, National Renewable Energy Laboratory, Golden, Colorado, USA R. Wickramasinghe (Speaker), Colorado State University, Fort Collins, Colorado, USA - [email protected]

A major obstacle to the large scale industrial use of biobased products and biofuels is the lack of efficient, cost-effective separation methods. Separations operations currently account for 60- 80% of the processing costs of most mature chemical processes. Here we focus on the development of membrane extraction as a low cost, robust separation process in future biorefineries. As membrane extraction is non- dispersive it overcomes all of the disadvantages of conventional extraction. Acetic acid is produced during thermochemical pretreatment of lignocellulosic biomass. It is a weak acid that is strongly inhibitory to microorganisms used for bioconversion of sugars. Removal of acetic acid could be essential for increasing ethanol yields during fermentation. We have conducted experiments using dilute sulfuric acid pretreated corn stover. Acetic acid, in its protonated form, was extracted into an organic phase consisting of octanol and Alamine 336, a tertiary amine, containing 8-10 carbon aliphatic chains. Importantly, acetic acid removal is most efficient at pH values below 4.8, the pKa of acetic acid, thus no pH adjustment is required after pretreatment. Further as sulfuric acid is co- extracted the pH of the hydrolysate increases during extraction. Our results indicate co- extraction of furfural, hydroxymethylfurfural, acid soluble lignin and other phenolic compounds. Thus addition of membrane extraction to remove acetic acid may simplify and/or eliminate current hydrolysate detoxification technologies such as overliming. Development of a practical membrane extraction process for removal of weak acids such as acetic acid depends on carefully choosing the organic diluent and extractant (octanol and Alamine 336 used here).

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Membrane Contactors – 3

Friday July 18, 3:30 PM-4:00 PM, O’ahu/Waialua

Operational Flexibility of Gas-Liquid Membrane Contactors for CO2 Separation

K. Fischbein (Speaker), University of Twente, Enschede, The Netherlands - [email protected] K. Nijmeijer, University of Twente, Enschede, The Netherlands M. Wessling, University of Twente, Enschede, The Netherlands

Objective CO2 is one of the major contributors to the greenhouse effect: the power and industrial sectors combined, account for about 60% of global CO2 emissions [1]. To prevent the emissions of CO2, capture and sequestration of CO2 from gas streams is essential. The traditional method of separating CO2 from other gases is amine scrubbing. Although high product yields and purities can be obtained, the disadvantage of this method is its high energy consumption - especially during desorption - in combination with a high liquid loss due to evaporation of the solvent. Membrane technology is a promising method of replacing conventional absorption technology. It has a high energy efficiency, is easy to scale-up because of its modular design, and it has a high area-to-volume ratio [2]. These advantages suggest that membrane separation is a viable alternative to conventional gas separation techniques. In this work, we use a membrane contactor to separate CO2 from natural gas. A membrane contactor combines the advantages of membrane technology with those of an absorption liquid. In a membrane contactor, CO2 diffuses from the feed gas side through the membrane and is then absorbed in the selective absorption liquid. The loaded liquid is circulated from the absorber to the desorber, which can be a traditional desorber or a second membrane contactor, in which desorption of CO2 occurs. The membrane acts as an interface between the feed gas and the absorption liquid. The selectivity of the process is not only determined by the membrane, but also the absorption liquid plays a significant role and contributes to the selectivity. Gas-liquid membrane contactors offer a unique way to perform gas- liquid absorption processes in a controlled fashion and they have a high operational flexibility. In this work, we investigate the effect of these operating parameters on the CO2/CH4 separation performance of the membrane contactor and identify the operating window for such a process.

Experimental Part Porous polypropylene hollow fibers (Accurel S6/2, obtained from Membrana GmbH, Germany) and asymmetric poly phenylene oxide membranes (normally used for gas separation; kindly provided by Parker Gas Separation, The Netherlands) were used as absorber and desorber in a membrane contactor for the separation of CO2/CH4 (20/80 vol.%). The use of asymmetric membranes with a dense top layer prevents penetration of the

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absorption liquid in the pores of the membrane and leads to a reduction in the loss of absorption liquid. Mono ethanol amine (MEA) - the traditional absorption liquid for CO2 removal - was used as the absorption liquid. The effects of the flow rate of the absorption liquid (72 - 315 ml/min), the feed gas pressure (1.2 - 3.5 bar) and the temperature difference between absorption and desorption processes (T = 0 - 35°C) were investigated, and the operating window for the membrane contactor process was identified.

Results The results of the multiple fiber contactor experiments show the effect of the operating parameters on the CO2/CH4 separation performance of the membrane contactor and identify the operating window for such a process. A comparison between the porous and the asymmetric fiber modules shows significant differences, especially concerning the pressure sensitivity. For the porous fiber modules, an increase in the feed pressure immediately results in increases in the permeabilities of both CO2 and - more especially - CH4, which results in a tremendous decrease in CO2/CH4 selectivity. The asymmetric fiber modules are more resistant to pressure fluctuations, and this thus increases the performance and the operating window for the process significantly. Apart from differences between the membranes types, some similar effects can be observed for both types of membranes; for example, an increase in the temperature difference between absorber and desorber significantly influences the process performance. The temperature of the desorber is especially important, because desorption is the limiting step in the process. With an increasing liquid flow rate, a maximum in productivity can be observed. Below this maximum, the capacity of the absorption liquid limits the process, whereas at higher flow rates mass transport limitations determine the performance. The results of the various experiments clearly show the influence of the different process parameters and thus define the operating window for such a process to separate CO2 from CH4.

1. 1 IPCC Special Report on Carbon dioxide Capture and Storage; http://www.ipcc.ch/activity/srccs/SRCCS_Chapter2.pdf.

2. B.D. Bhide, A. Voskericyan,S.A. Stern, Hybrid processes for the removal of acid gases from natural gas, Journal of Membrane Science, 140 (1998) 27

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Membrane Contactors – 4

Friday July 18, 4:00 PM-4:30 PM, O’ahu/Waialua

Effect of Spacer, Baffled and Modified Hollow Fiber Geometries in the Membrane Distillation Process

M. Teoh (Speaker), National University of Singapore, Singapore S. Bonyadi, National University of Singapore, Singapore T. Chung, National University of Singapore, Singapore - [email protected] M. Gryta, Szczecin University of Technology, Szczecin, Poland

For about three decades, Membrane distillation (MD) has been considered as a possible alternative for the conventional desalination technologies such as multi-stage flash vaporization (MSFV) and reverse osmosis (RO). However, MD has gained little acceptance and yet to be implemented in industry for several reasons: barrier of suitable MD membrane and module design, membrane pore wetting, low permeate flow rate & water flux (i.e., productivity) as well as uncertain energetic and economic costs. In this respect, opportunities therefore beckon membrane researchers to improve the permeate flux to bring MD closer to commercialization. Based on the MD mechanism, the obtained flux in MD depends both on the membrane permeation properties as well as the flow geometry in the membrane modules. A good flow geometry maintaining turbulence among the fibers can minimize the undesirable temperature polarization which leads to a lower driving force across the membrane and consequently a lower obtained flux. Therefore, research on the flux enhancement in MD can be divided into two large areas: (1) the fabrication of highly permeable membranes and (2) designing optimized membrane modules.

Because of the effect of temperature polarisation or temperature drop crossing membrane, heat transfer across the boundary layer from the bulk to the membrane surface often limits the rate of flux transfer in MD. Thus to improve mass transfer of flux in MD, researchers must minimise this phenomenon. An alternative approach to the flux enhancement in MD application lies in the modification of module design by spacers/baffles/turbulence promoters and modified hollow fiber geometries. By modeling the transport phenomena, the application of baffles increase the feed-side heat-transfer coefficient, which correspond to ~20% flux enhancements. Besides, it was observed that using spacers among the fibers may prevent the fibers from sticking together hence efficiently increase the effective membrane area ~33%. The un-straight geometry of the hollow fibers (braided and twisted) may act as a static mixer for the shell-side flow which can increase the associated heat-transfer coefficients and led to flux enhancements as high as 36% without inserting an external turbulent promoter. In overall, greater flux enhancements with modified hollow fiber membranes modules were achieved at higher feed temperatures.

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Membrane Contactors – 5

Friday July 18, 4:30 PM-5:00 PM, O’ahu/Waialua

Direct Contact Membrane Distillation: Studies on Novel Hollow Fiber Membranes, Devices, Countercurrent Cascades and Scaling

K. Sirkar (Speaker), New Jersey Institute of Technology, Newark, New Jersey, USA - [email protected] L. Song, New Jersey Institute of Technology, Newark, New Jersey, USA H. Lee, New Jersey Institute of Technology, Newark, New Jersey, USA F. He, New Jersey Institute of Technology, Newark, New Jersey, USA J. Gilron, Zuckerberg Institute for Water Research, Beer-Sheva, Israel B. Li, New Jersey Institute of Technology, Newark, New Jersey, USA P. Kosaraju, New Jersey Institute of Technology, Newark, New Jersey, USA Z. Ma, United Technologies Research Center, East Hartford, Connecticut X. Liao, United Technologies Research Center, East Hartford, Connecticut J. Irish, United Technologies Research Center, East Hartford, Connecticut

We have recently developed novel hollow fiber membranes and devices for recovering pure water from hot brine via membrane distillation (MD). Hot brine undergoes rectangular crossflow over the outer surface of highly porous hydrophobic polypropylene hollow fibers whose outside surface was coated with porous plasmapolymerized silicone-fluoropolymer coating to mitigate pore wetting and distillate contamination. In direct contact membrane distillation (DCMD) process using these fibers, cold distillate flows through the fiber bores which are large; the thickness of the highly porous wall is considerably larger than conventional membrane contactor hollow fibers. Brine crossflow, large fiber wall thickness, large fiber bore and the porous coating have yielded very high water vapor flux, high thermal efficiency, low temperature polarization and no distillate contamination. The DCMD studies were carried out sequentially with modules having a surface area of ~120 cm2, with larger modules having a surface area of 0.286 m2 and recently in a pilot plant at United Technologies Research Center with modules each having 0.61-0.66 m2 membrane surface area. This DCMD pilot plant was operated with hot brine at different salt concentration levels; sea water was also used. For brine feeds of 85-90oC, water vapor flux reached values of over 55 kg/m2-h independent of the scale of the hollow fiber membrane membrane modules or the salt concentration (up to 10%). Extended pilot scale operation demonstrated no salt leakage, stable and repeatable performance.

Modeling the direct contact membrane distillation behavior in both small (each having an area of 0.286 m2) and large-scale modules (each having an area of 0.61-0.66 m2) has been successfully implemented. A variety of module configurations were studied; the primary variables investigated were brine flow

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rate, distillate flow rate, inlet temperatures of the two streams, salt concentrations, etc.

Cost-efficient desalination technology was also developed successfully by integrating a countercurrent cascade of these novel crossflow hollow-fiber membrane-based direct contact membrane distillation (DCMD) devices and solid polymeric hollow fiber-based heat exchange (HX) devices. Each of the small DCMD membrane modules used for the countercurrent cascade had a surface area of 500 cm2. Studies were carried out in such a heat-integrated cascade using 2-8 modules representing 2-8 stages. A comprehensive numerical simulator was developed to successfully predict the experimentally observed performance of such a cascade. The thermal efficiency achieved experimentally in such a cascade was as high as 0.87. The highest GOR (gained output ratio) achieved reached around 6; heat loss to the environment from the heat exchanger limited so for the attainment of higher values. Fractional water recovery per pass reached almost 7%. Modeling results provide a guidance to cascade performance improvement. For example, unequal incoming brine and distillate flow rates can yield a GOR as high as 12 for ten stages in a countercurrent DCMD cascade unlike equal incoming brine and distillate flow rates. Numerical simulations yield reasonable cost figures for desalination.

Scaling studies carried out in DCMD using CaSO4 as the scaling salt indicate that even when there was significant precipitation of CaSO4, there was no effect on the membrane vapor flux or brine pressure drop. The induction period for CaSO4 nucleation decreased with increased feed brine temperature (60-90°C) and increasing level of the degree of supersaturation. We observed no flux reduction inspite of extensive scaling deposits in solution. Similar results were obtained with CaCO3 over a wide range of temperature and SI values (11 to 64). Mixed CaCO3 + CaSO4 systems behaved similarly except the scaling deposits were extensive and somewhat stickier. Scaling studies with CaSO4 on a polymeric solid hollow fiber heat exchanger did not lead to a decrease in heat transfer performance although there was a minor increase in pressure drop. Crossflow with coated fibers prevented any flux reduction or distillate contamination by scaling deposits in the DCMD device whereas parallel flow did not. Noncoated fibers in a DCMD device were susceptible to faster nucleation.

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Membrane Contactors – 6

Friday July 18, 5:00 PM-5:30 PM, O’ahu/Waialua

MEMFRAC - A New Approach to Membrane Distillation

E. Sanchez (Speaker), TNO (Netherlands Organisation for Applied Scientific Research), Delft, The Netherlands - [email protected] P. Koele, TNO (Netherlands Organisation for Applied Scientific Research), Delft, The Netherlands E. Meuleman, TNO (Netherlands Organisation for Applied Scientific Research), Delft, The Netherlands

Traditionally, membrane distillation uses macroporous hydrophobic membranes as surface for contacting a vapor and a liquid phase. One of the requirements for a membrane distillation process is that the membrane must not be wetted. Pore wetting may happen when surface active components are in direct contact with the membrane surface or when the pressure exceeds the liquid entry pressure. TNO has developed MEMFRAC as a new approach to circumvent these problems. MEMFRAC is an acronym of the words MEMbrane contactor and FRACtionating. The principle of MEMFRAC is based on the use of highly permeable dense membranes as a membrane contactor instead of using macroporous membranes. The presented work demonstrates that membrane contactors, based on dense asymmetric membranes, are a promising alternative packing material for distillation. Major advantages of this system are long term stability and no risk of pore wetting.

Within the present project several membrane types were tested. MEMFRAC contactors are made of extreme hydrophobic porous membrane that repels ethanol and water and mixtures thereof, poly (phenylene oxide) (PPO) asymmetric hollow fiber membranes, dense hydrophilic sheets and dense polypropylene asymmetric hollow fiber membranes. Based on extensive testing, the project was focused on the PPO membranes, because they were commercially available. The membrane structure consists of a macroporous sublayer in the inside and a thin highly permeable dense layer on the outside. This top layer prevents liquid penetration, while vapor can penetrate readily. The total membrane thickness is about 100 microns and the fibers have an outer diameter of about 0.5 mm. Special modules were developed for the purpose of MEMFRAC. A typical MEMFRAC module contains 2300 fibers per module resulting in a specific area as high as 3000 m2/m3. The performance of MEMFRAC has been tested for different organic solvent - water mixtures. The presentation will focus on the bench scale distillation plant for the separation of ethanol from water. Experimental tests have been carried out with different ethanol - water mixtures and operating at total reflux. The ethanol concentration at the MEMFRAC contactor inlet varied from 40 wt% to 80 wt%. For the highest concentrations, enrichments of about 19% are obtained. In this case the outlet

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concentration approaches the azeotrope composition. At lower concentrations, higher enrichments are obtained (up to 85%). Mass transfer efficiency has been investigated at different vapor loads (i.e. F- factor: vapor velocity times the square root of vapor density) ranging from 0.3 to 1 (m/s)(kg/m3)0.5. High fluxes can be obtained leading to an overall vapor phase mass transfer coefficient of about 1 x 10-3 m/s. The HETP increases slightly with increasing vapor loads, being as low as 13 cm for low vapor loads and as high as 18 cm for high vapor loads. Compared to random packings these values are substantially lower.

Results show high fluxes, robustness and long term stability in operation (continuous stable operation of more than 240 hours). MEMFRAC shows great potential especially in situations where small foot prints are beneficial (e.g. distillation on platforms, off-shore applications).

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Packaging and Barrier Materials – 1 – Keynote

Friday July 18, 2:15 PM-3:00 PM, Wai’anae

New Developments in the Measurement of Multi-Component Sorption in Barrier Polymer Materials: A Key Step towards the Modeling of Fuel Tank Permeability

A. Jonquieres (Speaker), Nancy Universite, Nancy, France - [email protected] R. Clement, Nancy Universite, Nancy, France C. Kanaan, Nancy Universite, Nancy, France B. Brule, Arkema, Serquigny, France H. Lenda, Nancy Universite, Nancy, France P. Lochon, Nancy Universite, Nancy, France

For different reasons including safety and weight reduction of vehicles, most of the fuel tanks are currently made of multi-layer barrier polymer materials which have to comply with ever more demanding environmental international regulations [1]. These fuel tanks are so poorly permeable that the measurement of their permeability usually requires almost one year, i.e. the time necessary to reach the steady state in contact with the multi- component fuel mixture. In this highly demanding context, the modelling of their permeability would allow to bypass the measurement delay and to predict and optimize their permeation properties, within a period of time compatible with the fast evolution of the international regulations limiting the fuel emissions per vehicle.

According to the sorption-diffusion model [2], the permeation of a fuel mixture through of a barrier polymer film involves two elementary steps. In the first sorption step, a part of the fuel mixture is absorbed at the upstream side of the film. In the second step, the absorbed species diffuse across the polymer film according to their activity gradients defined by the sorption step. Therefore, determining the sorption properties of the different barrier polymer materials of fuel tanks is truly indispensable for modelling their permeability [3].

However, the barrier polymer materials used in fuel tanks are usually characterized by very low sorption levels which can nevertheless vary by several orders of magnitude depending on the absorbed solvent. Therefore, quantitatively determining their sorption properties remains a true technical challenge never taken up to the best of our knowledge. This communication describes our last progress made in collaboration with the worldwide chemical company Arkema for the quantitative determination of these multi-component sorption properties.

A new semi-automated desorption experimental set-up was thus developed for measuring the sorption properties of these barrier polymer materials in contact

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with model fuel mixtures. This fairly complex apparatus combines a desorption mini-oven with on-line gas chromatography (GC), to allow the on-line analysis of the desorbed mixture during a given desorption cycle. By a proper optimization of the measurement conditions in real time, in particular the GC sensitivity range and the desorption temperature profile, a very high sensitivity (0.1 microgram) was easily obtained for the measured weights.

This very high sensitivity eventually enabled to determine partial sorption data differing by three orders of magnitude for the same experiment which, to the best of our knowledge, has never been reported so far. Several examples for multi- component sorption results will be discussed with a particular focus on two leading polymer materials used in multi-layer fuel tanks (high density polyethylene HDPE and an ethylene-vinyl alcohol copolymer EVOH) [4]. The whole set of sorption data revealed opposite trends for their swelling in model fuel mixtures ethanol/i-octane/toluene for a wide range of compositions typical for the various types of fuels. While HDPE absorbed preferentially the apolar hydrocarbons, EVOH displayed a very strong affinity towards ethanol. Another striking fact was that both barrier materials showed very different affinities for both hydrocarbons with a preferential sorption of toluene owing to its strong polarizability, in good agreement with former observations made for related permeability measurements [3].

References :

[1] T. McNally, G.M. McNally, S.B. Byrne, W.R. Murphy, and I. Gilpin, Annual Technical Conference - ANTEC, Conference Proceedings, 3 (1998) 2642- 2646.

[2] J. Wijmans, R. Baker, Journal of Membrane Science 107 (1995) 1-21 (review).

[3] M. Nulman, A. Olejnik, M. Samus, E. Fead, and G. Rossi, Society of Automotive Engineers, Special Publication, SP-1365 (1998) 41-48.

[4] R. Clément, C. Kanaan, B. Brulé, H. Lenda, P. Lochon, A. Jonquières, Journal of Membrane Science 302 (2007) 95-101.

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Packaging and Barrier Materials – 2

Friday July 18, 3:00 PM-3:30 PM, Wai’anae

Fundamental Exploration of Metal-Catalyzed Oxidation in Styrene-Butadiene-Styrene Block Copolymers

K. Tung (Speaker), The University of Texas at Austin, Austin, Texas, USA C. Ferrari, The University of Texas at Austin, Austin, Texas, USA R. Li, The University of Texas at Austin, Austin, Texas, USA K. Ashcraft, The University of Texas at Austin, Austin, Texas, USA B. Freeman, The University of Texas at Austin, Austin, Texas, USA - [email protected] D. Paul, The University of Texas at Austin, Austin, Texas, USA

Barrier films are essential for packaging to prolong product shelf life, and films that have exceptional oxygen barrier properties are valuable for food packaging. One method to improve oxygen barrier properties is to incorporate reactive groups in the membranes[1, 2]. In the presence of a transition metal catalyst, these reactive groups capture, or scavenge O2 as it diffuses through a film.

The ultimate goal of this study is to investigate the performance of scavenging polymers in the form of block copolymers containing a scavengable block, such as polybutadiene, and a block, such as polystyrene, that might compatibilize the material with a matrix barrier resin, such as polystyrene. This study will eventually lead to the investigation of multi-layered systems of styrene-butadiene-styrene (SBS) block copolymers and polystyrene.

The rate and amount of oxygen uptake as a function of metal catalyst concentration, film thickness, and oxygen partial pressure were characterized using an SBS block copolymer with the following characteristics: MW: 114,800, 12.5 % polystyrene, and 76 % vinyl structure. The experiments were performed at 30 °C. Effect of metal-catalyzed oxidation on polymer morphology was also studied through microscopic and spectroscopic characterization.

The experimental mass uptake data were used to characterize oxidation kinetics as a function of catalyst (cobalt neodecanoate) loading. Induction periods were observed in lower catalyst loadings. Mass uptake did not scale linearly with catalyst concentration; there was an optimum catalyst loading. Different values of optimum catalyst concentrations were found in homopolymers (i.e., poly(1,2-butadiene) and poly(1,4-butadiene)) and the SBS block copolymer. Film thickness also had an effect on oxidation kinetics. Mass uptake values increased as film thickness decreased; in other words, oxidation is more efficient as the film becomes thinner. It was hypothesized that surface oxidation takes place as O2 molecules diffuse through SBS films. AFM images revealed a hard region, which was rationalized to be the oxidized layer, at the film surface. Normalizing by film surface area shows a close overlap of mass uptake data of various thicknesses,

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supporting the hypothesis of surface oxidation. That is, the oxygen first oxidizes the surface of the samples and then moves into the film, in the form of a front, and gradually oxidizes the polymer deeper and deeper into the sample. In oxygen partial pressure experiments, mass uptake increases as oxygen content increases. A shrinking core mathematical model was developed to predict oxygen concentration as a function of time and distance into the film.

Reference:

1. Cochran, M. A.; Folland, R.; Nicholas, J. W.; Robinson, M. E. R. Packaging. 5,639,815, 1997

2. Cochran, M. A.; Folland, R.; Nicholas, J. W.; Robinson, M. E. R. Packaging. 5,021,515, 1991

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Packaging and Barrier Materials – 3

Friday July 18, 3:30 PM-4:00 PM, Wai’anae

The Effect of Reaction Conditions on Oxidation of Metal-catalyzed Poly(1,4-butadiene)

H. Li (Speaker), The University of Texas at Austin, Austin, Texas, USA K. Tung, The University of Texas at Austin, Austin, Texas, USA B. Freeman, The University of Texas at Austin, Austin, Texas, USA - [email protected] M. Stewart, Global PET Technology, Eastman Chemical Company, Kingsport, Tennessee, USA J. Jenkins, Global PET Technology, Eastman Chemical Company, Kingsport, Tennessee, USA

Oxygen scavenging polymers, which are polymeric materials that trap and effectively immobilize oxygen, have potential for large applications in the packaging industry. Incorporating an oxygen scavenging polymer into the package wall can lead to a significant improvement in oxygen barrier properties. However, there are very few studies of the fundamental structure/property relations governing oxygen scavenging, and this research is focused on addressing this shortcoming in the literature.

In this study, we used a simple, accurate instrument for testing large numbers of samples. Oxygen mass uptake was determined by a non-invasive oxygen sensor based system, and experiments were performed with metal-catalyzed poly(1,4-butadiene) films. For comparison, oxygen uptake was also measured using an analytical balance, and similar results were obtained. Experimental results showed that poly(1,4-butadiene) was oxidized under various storage conditions, and a maximum of 30 weight percent oxygen uptake was observed. A highly oxidized layer was found at the membrane surface after the reaction. The oxidized layer thickness was determined by measuring the oxygen mass uptake of film with different thicknesses.

This presentation also discusses the influence of reaction conditions on oxidation rate and oxygen mass uptake of poly(1,4-butadiene). Specifically, the effect of reaction temperature, oxygen partial pressure, and catalyst concentration on oxygen mass uptake, oxidation rate, and change in membrane permeability will be discussed. Experimental results reveal that by controlling the reaction conditions, an efficient and long-term oxygen scavenging membrane can be obtained. These results not only provide an understanding of oxidation in these membranes, but also could lead to the development of new scavenging packaging materials and prediction of their optimum working conditions.

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Packaging and Barrier Materials – 4

Friday July 18, 4:00 PM-4:30 PM, Wai’anae

On the Nature of Gas Barrier of Ethylene Vinyl Alcohol Copolymers.

S. Nazarenko (Speaker), University of Southern Mississippi, Hattiesburg, Mississippi, USA - [email protected] G. Chigwada, University of Southern Mississippi, Hattiesburg, Mississippi, USA J. Brandt, University of Southern Mississippi, Hattiesburg, Mississippi, USA B. Olson, University of Southern Mississippi, Hattiesburg, Mississippi, USA A. Jamieson, Case Western Reserve University, Cleveland, Ohio, USA

Ethylene vinyl alcohol copolymers (EVOH) play an important role in the food packaging industry. These copolymers are typically produced via hydrolysis of ethylene vinyl acetate random copolymers. Gas barrier of EVOH copolymers depends on vinyl alcohol content. EVOH copolymers, especially with high vinyl alcohol content, are excellent gas barriers primarily due to hydrogen bonding (H-bonding) formed by the hydroxyl moieties. In turn, H-bonding results in the increase of cohesive energy density (CED) of a polymer and decreases its free volume. Both factors contribute to low gas diffusivity and high gas barrier of EVOH copolymers. The fundamental role of free volume and CED on diffusion behavior and their fundamental interrelationship, however, has not been completely understood as yet. Because of its structural simplicity EVOH copolymers is an excellent model system for studying the effect of H- bonding on gas diffusion.

EVOH copolymers with various ethylene contents (0, 24, 27, 32, 38, 44, 48, 60, 75, 82 and 95 mol %), were used in this work. EVOH 0-60 mol % are commercial products, EVOH 75-95% were prepared by hydrolysis of ethylene vinyl acetate (EVA) copolymers. Thin films of the ethylene vinyl alcohol copolymers were prepared by compression molding. Glass transition temperature of copolymers was investigated by DSC. The crystallinity was investigated by WAXS. The state of hydrogen bonding was determined by FTIR. Cohesive energy of the copolymers was calculated using Hoy group contribution method as well as determined by conducting molecular dynamics simulations using commercially available software Accelrys. The free volume at various temperatures was probed by Positron Annihilation Life-Time Spectroscopy (PALS). Oxygen transport measurements were conducted using standard MOCON Oxtran-2/21 facility at 0%RH. Oxygen flux curves versus time were measured. The flux data were fit to the solution of Ficks second law. Oxygen permeability (P) and diffusivity (D) data were generated from the fit. Oxygen solubility coefficient (S) was calculated from P and D. Activation energy for oxygen diffusivity for selected copolymers, however covering the entire range of composition, was measured by running the experiments at various temperatures above as well as below glass transition temperature of the copolymers.

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Historically, all the approaches describing gas diffusion in polymers can be roughly divided in two categories, based on free volume model and the activation molecular models based on Eyring transition state theory, which take into account the cooperative penetrant�polymer chain motions, chain rigidity and intermolecular forces. Although gas transport characteristics exhibit a general correlation with free volume, alone free volume can not adequately describe gas barrier. The chain rigidity and the strength of intermolecular interaction are two additional important factors which are manifested via activation energy. Currently, there is a tendency towards unification of these two different approaches as the process of diffusion in the glassy state indeed depends on free volume while at the same time is a thermally activated process. The main objective of this work was to develop fundamental understanding of gas diffusion in EVOH copolymers as it is related to free volume characteristics and cohesive energy density.

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Packaging and Barrier Materials – 5

Friday July 18, 4:30 PM-5:00 PM, Wai’anae

Confined Crystallization of PEO in Nanolayered Films for Improved Gas Barrier

H. Wang (Speaker), Case Western Reserve University, Cleveland, Ohio, USA B. Freeman, The University of Texas at Austin, Austin, Texas, USA A. Hiltner, Case Western Reserve University, Cleveland, Ohio, USA - [email protected] E. Baer, Case Western Reserve University, Cleveland, Ohio, USA

The goal of this project is to produce gas barrier materials for food packaging with controlled atmosphere. Crystallization of polymer chains in a confined space can generate unique morphologies and may impact the properties of the polymeric material, such as the mechanical strength and gas barrier. Previously confined polymer crystallization has been extensively studied in block copolymers utilizing the nanoscale structure formed by their self-assembly. The enabling technology of layer-multiplying coextrusion in the Center for Layered Polymeric Systems (CLiPS) provides a unique opportunity to study the confined crystallization of commercial polymers. In this study, assemblies of highly crystalline poly (ethylene oxide) (PEO) layers with thickness ranging from 4 micron to 100nm were achieved by ‘forced assembly’ with ethylene-co-acrylic acid copolymer (EAA). When the PEO layer thickness was in the micron scale (1-4 micron), the PEO crystal orientation was isotropic and the gas barrier of PEO layer was the same as the non- layered PEO. Upon further decreasing the PEO layer thickness to around 100nm, atomic force microscopy and wide angle X-ray diffraction showed that the long PEO lamellar crystals were aligned parallel to the layer direction in these nanolayered films. The PEO/EAA nanolayered films exhibited greatly improved gas barrier properties with the oxygen and carbon dioxide permeability one order of magnitude lower than the microlayered films. The improved barrier was attributed to the increased diffusion tortuosity in the PEO layers because the long, impermeable PEO crystals were aligned perpendicular to the gas diffusion direction. This observation reveals the potential of making better barrier films from conventional polymeric materials.

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Packaging and Barrier Materials – 6

Friday July 18, 5:00 PM-5:30 PM, Wai’anae

Relationship between Biaxial Orientation and Oxygen Permeability of Polypropylene Film

Y. Lin (Speaker), Case Western Reserve University, Cleveland, Ohio, USA P. Dias, Case Western Reserve University, Cleveland, Ohio, USA H. Chen, The Dow Chemical Company, Freeport, Texas, USA A. Hiltner, Case Western Reserve University, Cleveland, Ohio, USA - [email protected] E. Baer, Case Western Reserve University, Cleveland, Ohio, USA

Biaxially oriented polypropylene (BOPP) films were produced by simultaneous and sequential biaxial stretching to various balanced and unbalanced draw ratios. The BOPP films were characterized in terms of density, crystallinity, refractive index, oxygen permeability and dynamic mechanical relaxation behavior. It was found that the density and crystallinity of BOPP films decreased as the area draw ratio increased. Sequential stretching led to a slightly lower density than simultaneous stretching to the same draw ratio. Moreover, sequential stretching produced lower orientation in the first stretch direction and higher orientation on the second stretch direction compared to simultaneous stretching. The study confirmed the generality of a one-to- one correlation between the oxygen permeability of BOPP films and the mobility of amorphous tie chains as measured by the intensity of the dynamic mechanical beta-relaxation. Moreover, the study established the correlation for commercially important sequentially drawn BOPP films with an unbalanced draw ratio. For the specific resin used in this study, the oxygen permeability also correlated with the z- direction refractive index. Finally, the chain mobility in the stretch direction was found to depend on the final stress during stretching.