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DEAKIN UNIVERSITY 15-19 FEBRUARY, 1993

CONTENTS

Preface 2

Acknowledgements 3

Guests of Honour 3

Participants not Presenting Papers 4

Seminar Program 6

Abstracts 15

PREFACE

Welcome to the seventeenth of a series of infonnal meetings, initiated by Tom Healy and Bob Hunter. The meetings have, over the past twenty five years, grown in size and scope but it is hoped that the underlying philosophy has remained untouched. This philosophy has always been to provide a forum for post-graduate students and the occasional new 'post-doc' to present their work to an audience of their peers, academic supervisors and a few industry and CSIRO scientists.

This year, we expect to accommodate over 140 participants and although the original laid-back nature of the gathering is severely tested by size of the conference, in-fonnality is still the key. It is hoped that the constructive criticism all speakers are expected to withstand both during and after their presentations is carried through to the infonnal mixer/drinks sessions and into longer tenn collaborations.

This year the meeting is being hosted by the University of Melbourne group and is being held at Deakin University. We welcome as guests Professor Mats Almgren from Uppsala University in Sweden and Professor David Beaglehole from Victoria University of Wellington. We also welcome students and other participants from a large numberof research groups from both within Australia and overseas.

Special thanks goes to Robert Hall and Stephanie Faulkner for their efforts in organising the conference program and getting the 'show on the road.'

Enjoy the science, enjoy the conference.

1&J~ Peter Scales February 1993

2

ACKNOWLEDGEMENTS ·

The following organisations have provided substantial financial support for this Conference and their contributions are warmly acknowledged:

Albright & Wilson (Australia) Ltd

CSIRO (Division of Mineral Products)

IIlsmelt Corporation Pty Limited

Sola International Holdings Ltd

CRA Technological Resources Pty Limited

Comalco

ICI Engineering (Australia) Pty Ltd

Obviously the individual attendees have also contributed financially to the running of the Conference as have their host Institutions. This support is invaluable.

GUESTS OF HONOUR

Professor Mats Almgren, Uppsala University, Sweden

Professor David Beaglehole, Victoria University of Wellington, NZ

3

PARTICIPANTS NOT PRESENTING.PAPERS

ANU LaTrobe UCNV

David Antelmi Bruce Johnson Richard Pashley John Wells Hugo Christenson Robert Corkery Monash University Mark Knackstedt Barry Ninham Ian McKinnon ThomasZemb Brent Ward

Ron Beckett CSIRO Chinlha Fonseka

Barry Hart Calum Drummond David Elliot University of Sydney Neil Furlong George Gurjaklis Robert Hunter Elke Paschinger Dick O'Brien Rob Urquhart Bill Rowlands Thomas Horr Greg Warr

Aust. Ddence Force Academy RMIT

Carinna Tong Bill van Megan

Dulux Aust. ICI Paints Swinburne University

Craig Meekings Ian Harding David Mainwaring

Glaxo University or Illinois

Tim Bowser

ICI Australia

Sylvia Underwood Joanne Kuluveovski

Kelly Miller

DuPont Agricultural Products

Clarence Hennansky

4

University of Melbourne

May-Yoong Lee Yee Leong Jilska Perera Steven Camie Derek Chan Kurt Liffman John Sader Lee White Paul Mulvaney Simon Biggs Stephanie Faulkner Michelle Gee Franz Grieser Tom Healy Hennan Mansur Mark Marychurch Satoshi Nishimura Peter Scales

University or NSW

Vicki Chen Mark Collings Robert Lamb Catherine Pritchard Peter Timbrell

University or Queensland

Geoff Barnes Gwen Lawrie Jian Peng

5

University or South Australia

Daniel Fornasiero Robert Hayes Roger Hom Clive Prestidge John Ralston Jarl Rosenholm Darren Simpson Bill Skinner Roger Smart

Uppsala University

Mats Almgren

Victoria University of Wel~ngton

David Beaglehole

Weizmann Institute or Science

Sam Safran

Other

David Dunstan

..

12.30 1.30 1.30 3.00

3.00 3.30 3.30 ·s.

9.00 11.

REGISTRATION

Micelles (6)

Pashle

MIXER

Banon College Common Room

-

CONFERENCE PROGRAM

TUESDAY

Thin films (6)

Barnes

Thin films (6)

Fur/on

Synthesis (5)

Smart

Instrumental methods(4)

Beckert

WEDNESDAY I THURSDAY BREAKFAST

Instrumental I Growth & methods(6) Rheology (6)

Horn I Ralston MORNING TEA

Dispersions I G & R (3) (6) Particle

lnteracrions(3) Hunter I Gee

LUNCH

Dispersions (4)

Heal

Particle Interactions(3)

Char and Mod (3)

O'Brien

CONFERENCE DINNER

MlXER / DISCUSSIONS Barron, College Common Room

Dining Room

FRIDAY

Char & Mod(3) Adsorption(3)

Lamb

Adsorption (6)

CLOSE Grieser

SEMINAR PROGRAM

MONDAY (t denotes evening se~ion)

MONDAY 15th FEBRUARY

3.15 - 3.30

SESSION 1

Welcoming Remarks Professor Thomas Healy

Chair: Professor Richard Pashley

Micelles and Microemulsjons .

3.30- 3.45

3.45 -4.00

4.00- 4.15

4.15 - 4.30

4.30 - 4.45

4.45 - 5.00

Rachel Hobson (University of Melbourne) Surface Potential Measurements in Mixed Micelle Systems Guilan Tan (University of Sydney) Microemulsion Polymerization Kathryn McGrath (ANU) Polymerization of Surfactant Liquid Crystalline Phases Peter Pieruschka (ANU) Random Interfaces and the Physics of Microemulsions Bronwyn Battersby (University of Queensland) Cryo-Electron Microscopy of Phospholipid Suspensions Christopher Garvey (University of Sydney) Specific Ion Effects in Dodecylsulfate Micelles

TUESDAY 16th FEBRUARY

SESSION 2

Thin films m 9.00- 9.15

Chair: Dr. Geoff Barnes

Fiona Elms (University of NSW) f ~\ Metal Hydride Chemical Vapour Deposition

7

9.15 - 9.30 Leong Mar (University ofNSW) Organometallic Deposition of ZnO

9.30 - 9.45 Frank Caruso (University of Melbourne) Determination of Lateral Diffusion Coefficients in Air­Water and Langmuir-Blodgett Films by Fluorescence Quenching Techniques

9.45 - 10.00 Jason Walling (University of WA) Reactivity of Self-Assembled Monolayers of Alkylsiloxanes on Oxidized Silicon Substrates

10.00 - 10.15 Brendan Sinnamon (University of Queensland) Langmuir-Blodgett Deposition of Selected Long Chain Macrocycles onto Quartz Piezoelectric Crystals

10.15 - 10.30 Rob Hall (University of Melbourne) Spectroscopic Studies of Hemicyanine Monolayers

10.30 - 11.00 MORNING TEA

SESSION 3 Chair: Dr. Neil ~urlong

Thin Films an 11.00 - 11.15 Sarah Gardiner (Massey University)

Ultramicro Biosensors 11.15 - 11.30 Tina Aquino-Binag (University of NSW)

Surface Studies of Quinhydrone pH Sensors: Fabrication and Characterisation

11.30- 11.45 Bon Than-Trong (University of NSW) .(_~ \\-e.~v'\. Vapour Deposition Polymerization of Polyimide

11.45 - 12.00 Eric Weisser (University of Melbourne) Miscible Interface Stability in Hele-Shaw Flows

12.00- 12.15 Markus Borbach (University ofNSW) Thin Fe Films Deposited on Copper

12.15- 12.30 Martin Puchert (University ofNSW) Intrinsic Stress and Growth of Magnetron Sputtered Films

12.30- 1.30 LUNCH

8

SESSION4 Chair: Professor Roger Smart

Synthesis and Preparation

1.30 - 1.45

1.45 - 2.00

2.00- 2.15

2.15 - 2.30

2.30- 2.45

2.45 - 3.00

3.00- 3.30

SESSIONS

Mick Bjelopavlic (University of SA) Synthesis of Novel Organic Collectors for the Flotation of Zircon Katrina Drummond (Monash University) Formation of Latex Particles Irene Baker (CSIRO) Sucrose Based Surfactants - Structure and Biodegradability Ze Huai Bill Chen (University of SA) Synthesis of Naphthalene Derivatives Ludger Pille (University of Melbourne) Synthesis of Microgel Particles and their Characterisation by Gel Permeation Chromatography with on line Multi Angle Laser Light Scattering and Refractive Index Detection .P4\.--> ~c.\ EA\ ,tr\ (,0 \ RO

AFfERNOON TEA

Chair: Dr. Ron Beckett

Instrumental Methods m t8.00- 8.15

t8.15 - 8.30

t8.30- 8.45

t8.45 - 9.00

Laurence Meagher (ANU) Direct Measurement of Surface Forces Important in the Fouling of Micro-Filtration Membranes Deirdre Murphy (Monash University) Separation Behaviour of Micron Sized Particles in Sterle Hyperlayer Field-Flow Fractionation Erica Wanless (ANU) An Electrochemical Study with the Atomic Force Microscope Stephen Au Yeung (University of Melbourne) Formation of Gold Sols Using Ultrasound

9

WEDNESDAY 17th FEBRUARY

SESSION6 Chair: Professor Roger Hom

Instrumental Methods cm 9.00- 9.15

9.15-9.30

9.30- 9.45

10.00 - 10.15

10.15 - 10.30

10.15 - 10.30

10.30 - 11.00

SESSION7

Dispersions m

Paul Rider (University of Sydney) The Dynamic Mobility of a Suspension of Interacting Particles Melanie Carasso (University of Sydney) Electroacoustic Study on Unstable Colloids Paul Pigram (University of NSW) Mass Spectrometry of Surfaces { Andrea O'Connor (University of Melbourne) ~ eA -<..f" · Multicomponent Interactions in Protein Electrophoresis Reshmi Sharma (Monash University) Physical Characterization, Quantification and Biomass Determination of Bacteria Using Sedimentation Field­Flow Fractionation Christine Mangelsdorf (University of Melbourne) High Frequency Colloidal Electrokinetics

MORNING TEA

Chair: Professor Robert Hunter

11.00 - 11.15 Mirjana Prica (University of Melbourne) The Surface Properties of Zirconia in Aqueous · Solutions

I 1.15 - 11.30 Minghua Mao (University of SA) Flotation of Zircon and Adsorption Studies in the Presence of Sodium Alkylamine Bis Methylenephosphonate

11.30- 11.45 David Atkins (ANU) Heterocoagulation

10

11.45 - 12.00 Nhol Kao (RMll) Dynamic Measurements on Model Dispersions

12.00 - 12.15 Lorraine Staehr (LaTrobe UCNV) Issues in Monte Carlo Simulation

12.15 - 12.30 Mr Sung (Swinburne University) Behaviour of Soluble Coal Components

12.30 - 1.30 LUNCH

SESSION 8 Chair: Professor Thomas Healy

Qi5persions W>

ts.oo- s.1s

ts.1s -s.3o

tsJO- 8.45

ts.4s -9.oo

Chris Greet (University of SA) Aotation of Hellyer Galena Warwick Holt (University of Melbourne) Colloidal Interaction During Sedimentation and Pressure Filtration Joan Thomas (University of SA) Dissolution of Sulphides in Aqueous Solutions Jim Stankovic (University of Melbourne) Calculation of the Electrostatic Potential and Force Between Identical Spherical Colloidal Particles - the Poisson Boltzmann Theory

THURSDAY 18th FEBRUARY

SESSION9 Chair: Professor John Ralston

Growth and Bbeolon or Particles m 9.00 - 9.15

9.15 - 9.30

Mruk Zirnsak (University of Melbourne) Laminar Aow of Dilute Solutions of Semi-Rigid Rod Molecules through an Abrupt Tubular Contraction Trina Dreher (University of Melbourne) The Effect of Fluid Hydrodynamics on Droplet Coalescence

11

9.30 - 9.45 Olivier Spalla (ANU) Ordering of Small Particles under Osmotic Stress

9.45 - 10.00 Petra Liddell (University of Melbourne) The Rheology of Titanium Dioxide Pigment Solutions

10.00 - 10.15 James Gunning (University of Melbourne) Fluctuation Forces due to Elastic Vibrations

10.15 - 10.30 Xiaodong Zhang (ANU) Lattice Gas Studies of Porous Media Flow in Three

.. Dimensions

10.30 - 11.00 MORNING TEA

SESSION 10 Chair: Dr. Michelle Gee

Growth and Bbeotou or Particles an 11.00 - 11.15 Robert Mun (University of Melbourne)

Break-up of Laminar Jets 11.15 - 11.30 Jane Wright (University of Melbourne)

Diffusion in Dilute Polymeric Liquids 11.30 - 11.45 Stuart Henderson (RMIT)

Growth of Colloidal Crystals Particle Interactions m 11.45 - 12.00 David Hewitt (University of SA)

Bubble/Particle Interactions 12.00 - 12.15 Ian Larson (University of Melbourne)

Direct Force Measurements Between TiO2 Surfaces 12.15 - 12.30 Marilyn Karaman (ANU)

Surface Properties of a Trivalent Cage Surfactant Investigated using Atomic Force and Confocal Microscopy

12.30 - 1.30 LUNCH

12

SESSION 11 Chair: Dr Dick O'Brien

Particle Interactjops ll>

1.30- 1.45

1.45- 2.00

2.00- 2.15

Peter Clarke (University of SA) The Interaction of Metal Ion Hydrolysis Products with Sulphide Minerals Vincent Craig (ANU) Bubble Coalescence & Electrolyte Effects Matthew Fielden (University of SA) Measurement of the Force Between a Silica Flat and Silica Sphere in Aqueous CaCl2 Solutions

Surface Characterization and Modjracatioa m 2.15 - 2.30

2.30 - 2.45

2.45 - 3.00

3.00- 3.30

Andrew Rider (University of NSW) Surface Studies of Adhesion Failure Ge Li (University of Sydney) The Deposition of Sterically Stabilised Particles onto Polymer Surfaces

AFTERNOON TEA

FRIDAY 19th FEBRUARY

SESSION ll Chair: Associate Professor Robert Lamb

Surface Characterization and Modj[icatjon OU

9.00- 9.15

9.15 - 9.30

David Power (University of Melbourne) Characterisation of Hydraulic Fracturing Fluids Belinda Braggs (University of SA) The Effect of Surface Modification by an Organosilane on the Electrochemical and Rheological Properties of Kaolinite

13

9.30- 9.45

Adsorption m

James RanvilJe (Monash University) Elemental Analysis of Colloidal Particles by SdFFF­ICP-MS

9.45 - 10.00 Julie Angerosa (Swinburne University) Adsorbing Colloid Flotation of Mercury(II)

10.00 - 10.15 Gayle Morris (University of SA) The Depression of Talc Using Polymeric Organic Molecules

10.15 - 10.30 John Morgan (University of Sydney) Measurement of the Selective Adsorption of Ions at an Air/Surfactant Solution Interface

10.30 - 1 l.00 MORNING TEA

SESSION 13 Chair: Dr. Franz Grieser

Adsorption cm 11.00 - 11.15 Gillian Fairthome (University of SA)

Thionocarbamates as Collectors for Sulphide Mineral Flotation

11.15 - 11.30 Jenny Simmons (University of Melbourne) Adsorption of Polyphosphates onto Zirconia Colloids

11.30 - 11.45 David Lewis (Swinburne University) Adsorbing Colloid Flotation of an Organic Dye

11.45 - 12.00 Michael Pietrobon (University of SA) The Surf ace Chemistry and Flotation Behaviour of Nickel Sulphide Minerals

12.00 - 12.15 Anthony Natoli (LaTrobe UCNV) The Effect of Temperature on the Adsorption of Cations onto Mineral Surfaces

12.15 - 12.30 Russell Crawford (Swinburne University) Heavy Metal Adsorption and Coprecipitation

12.30 - 1.30 LUNCH

14

SURFACE POTENTIAL MEASUREMENTS IN MIXED MICELLE SYSTEMS

Rachel Hobson (School of Chemistry, The University of Melbourne)

The relationship between the measured electrostatic surface potential of two mixed surfactant systems, n-dodecyloctaoxyethylene glycol monoether (Cl2E8) / sodium dodecyl sulphate (SOS) and Cl2E8 / n­dodecyltrimethylammonium chloride (DT AC) and the free ionic surfactant concentration in these mixtures has been examined. The surface potential measurements were based on the well established technique of using micelle solubilized acid-base indicators. Free monomer concentrations were determined from results obtained using the mixed micelle critical micelle concentrations and then processing this information using a non ideal mixed micelle theory. For the systems studied it has been found that a modulus change in the surlace potential per unit change in log (ionic surfactant concentration) is about 59 mV. This is in accordance with a relationship between the electrostatic surface potential of a charged micelle and its equilibrium monomer concentration.

NOTES

15

...

MJCROEMULSION POLYMERIZATION

Guilan Tan (Department of Physical Chen:iistry, University of Sydney)

Emulsion, miniemulsion, and more recently, microemulsion polymerization are processes that can produce polymeric particles of large molecular weights and small sizes dispersed in aqueous (or non-aqueous) media. Despite the fact that microemulsions were discovered in the early l940's, they were not polymerized until the early 1980's. Of particular interest is the mechanism of latex particle formation, which remains the subject of vigorous debate.

We will examine the mechanism of microemulsion polymerization and obtain various polymer glasses and characterize the polymers.

NOTES

16

POLYMERISATION OF SURF ACT ANT LIQUID CRYSTALLINE PHASES

Kathryn McGrath (Department of Applied Mathematics, ANU)

The self-assembly of several polymerisable surfactant molecules with water has been established using the techniques of Small-Angle-X-ray Scattering (SAXS) and Optical Microscopy. From the determined phase diagrams, specific regions have been chosen to be representative of the liquid crystalline phases formed in each surfactant/water system. These regions have been used to study the possibility of polymerising the surfactant while constrained within the geometry imposed on it by the liquid crystalline phase.

NOTES

(,.

17

RANOOMINIBRFACES AND THE PHYSICS OFMICROEMULSIONS

Peter Pieruschka (Department of Applied Mathematics, AuslralianNational University)

The Gaussian model of random interfaces (Cahn - Berk model) is related to the statistical mechanics of microemulsions by a variational approximation to the free energy. This requires the calculation of the structure factor as a function of surfactant and bulk concentrations and the bending modulus. Different scaling regimes for the coefficients of the structure factor are identified and we find that the real space correlations change from the typical damped Teubner ~ Strey sinusoid to a purely exponential decay as the surfacant volume fraction is lowered. Upon further decrease in surfactant concentration, the correlation length of the exponential decay diverges, signifying a phase seperation. The change in structure can also be observed in real space imageswhich show graphically the self-similarity of 'good' microemulsions and its breakdown close to the instability.

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CR YO-ELECTRON MICROSCOPY OF PHOSPHOLIPID SUSPENSIONS

Bronwyn Battersby (Department of Chemistry, The University of Queensland)

The imaging of liposomes in the electton microscope in their original, hydrated form has been the goal of researchers for many years; the evaporation of water under the high vacuum of the microscope being a major problem. Since the discovery that pure water could be cooled to a vitreous or glass-like state, rapid advances in cryo-electron microscopy have been made. The technique is now successfully being applied to a variety of aqueous systems including biological and synthetic membranes, viruses and membrane proteins. The specimen preparation involves plunging a thin film of the aqueous suspension into liquid propane at such a velocity (l.8 m s-1) that rearrangement of the water molecules into a macrocrystalline state is not possible. The suspended material becomes embedded in a layer of amorphous ice (vitrification), thereby avoiding structural damage from crystalline ice. After preparation, the specimen is viewed in a high resolution transmission electron microscope at -165°C.

When it is necessary to prepare specimens at temperatures different from ambient, the temperature of the sample must be carefully controlled until the moment of vitrification. A temperature and humidity-controlled environmental cabinet has been developed in order to prevent evaporation and premature exposure of the specimen to cold nitrogen vapours which could result in phase or concentration changes.

NOTES

19

SPECIFIC IONIC EFFECTS IN DODECYL-SULFATE MICELLES

Christopher Garvey (Department of Physical Chemistry, University of Sydney)

The interface of aqueous ionic micelles plays a crucial role in determining the interaction of lhe micelles with the solvent and the interactions between micelles in the solvent. These interactions are reflected in the critical micelleconcentration ( c.m.c.) and the slruCture of self-assembled aggregates formed in surfactant solutions under various conditions. If the concentration region just above the c .m .c. is considered a spherical hydrocarbon-like core surrounded by an interface made upofhydratedcounterions and headgroups, this provides a simple but adequate model of the micelle with a known surface area. Interactions between the headgroups on the micellar interface are electrostatic and counterions mediate the electrostatic repulsions between like charged headgroups determining the area per headgroup on the interface. Because of packing constraints, this becomes an important determinant in the micellar aggregation number. The degree of counterion binding and interfacial density of headgroups determine the interfacial charge density.

Using fluorescent probe techniques the surface potential and aggregation numberof a range of dodecyl-sulfates have been measured. The aggregation number indicates the number of charged headgroups per micellar interface and surface charge density calculated from surface potential allow the calculation oflhedegreeof surface counterion binding. Fractional ionisation has been estimated from conductivity below and above the c.m.c. and adsorption isotherms at the air/water interface of monomers give the area per surfactant headgroup al this interface (surface tension). Both provide good agreement with these less direct calculations.

NOTES

20

MET AL HYDRIDE CHEMICAL VAPOUR DEPOSITION

Fiona Elms (School of Chemistry, University of NSW)

No Abstract received NOTES

21

ORGANOMETALLIC DEPOSITION OF ZnO

Leong Mar (School of Chemistry, University of NSW)

No Abstract received NOTES

22

DE TERM.INA TION OF LATERAL DIFFUSION COEFFICIENTS IN AIR-WATER AND LANGMUIR-BLODGETT FILMS BY FLUORESCENCE QUENCHING TECHNIQUES

Frank Caruso (School or Chemistry, University or Melbourne)

Two-dimensional diffusion has been investigated in air-water and Langmuir­Blodgett films by studying the fluorescence quenching or a lipoidal pyrene derivative by two amphiphilic quenchers. The results have been analysed in the theoretical framework or diffusion-controlled quenching in a two­dimensional environment to yield the mutual lateral diffusion coefficients.

Both steady-state and time-resolved techniques were employed and yield data which shows clear evidence for the features predicted for diffusion­controlled reactions in two dimensions. Analysis of the steady-state quenching behaviour as a function of quencher concentration produced non-linear Stem-Volmer plots. The time-resolved measurements yielded a single exponential lifotime for the pyrene chromophore in the absence of quencher, providing evidence that it is not aggregated in the monolayer film. In the presence of quencher the decays were non-exponential.

The lateral diffusion coefficients were found to be of the order of 1 o-7 cm2

s-1 in the air-water monola._rerfilms. These values decreased with increasing surface pressure, reflectltfg an expected decrease of monolayer fluidity when the monolayer is compressed.

In the Langmuir-Blodgell films, the lateral diffusion coefficients were found to be a factorof 5 smaller than the corresponding air-water monolayer film. These values are comparable to those reported for lipid bilayers and natural membranes.

NOTES

23

REACTIVITY OF SELF-ASSEMBLED MONOLAYERS OF ALKYLSILOXANES ON OXIDISED SILICON SUBSTRATES

Jason Watling (Department of Chemistry, University of Western Australia)

Self-assembled organic monolayers have many potential applications in modem technology, in areas ranging from the control of swface properties (adhesion, wettability, etc) to the fabrication of new materials for sensors and non linear optical devices. For many of these potential applications to be realised, efficient methods for the preparation of self-assembled monolayers bearing reactive functional groups must be developed. The reactive function al groups would serve as sites from which monolayers could be elaborated into multilayer films (for new materials) or as sites where molecular fragments could be anchored to the monolayer surface (for device applications).

This presentation will describe recent studies of the chemistry of self­assembled monolayers of alkylsiloxanes on oxidised silicon wafers. These monolayers are of interest because they are more robust than most other types of self-assembled monolayers (such as monolayers of thiolates on gold) and so can withstand a range of chemical treatments. Our studies of the preparation of monolayers bearing reactive functional groups at their surfaces, and of the chemical reactivity of those functional groups, will be discussed.

NOTES

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24

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LANGMUIR-BLOOOETIDEPOSITIONOFSELECTEDLONGCHAIN MACROCYCLEO ONTO QUARTZ PIEZOELECfRIC CRYSTALS

Brendan Sinnamon (Department of Chemistry, The University of Queensland)

The surface chemistry properties of N-docosyl-1,4,7,10-tetraoxa-13-azacyclopentadecane (N-docosyl-Al5C5), N-docosyl-1,4,7 ,10,13-pentaoxa-16-azacyclooctadecane (N-docosyl-Al8C6) and N­carboxyeicosyl-1,4,7, lO-tetraoxa-13-azacyclopentadecane (N­carboxyeicosyl-Al5C5) were investigated by an examination of their respective surface pressure-area isotherms and area decay curves. A study of the surface-pressure area isotherms for each of the compounds revealed that N-carboxyeicosyl-A 15C5 has a lower fracture pressure than either of the alkyl chain macrocycles. Analysis of the area decay curves for all three compounds indicates that the monolayer collapses by dissolution of the amphipathic material within the aqueous subphase. The rate of dissolution of N-carboxyeicosyl-Al5C5 is considerably greater than for either of the other two ~ompounds, which exhibit similar rates of dissolution.

Langmuir-Blcxlgett deposition of both N-docosyl-A l 5C5 and N-docosyl­A l 8C6 onto a gold-plated microscope slide revealed that the first ten layers were deposited by the Y-type deposition mcxle. Langmuir-Blodgett depostion of N-docosyl-Al5C5 and N-docosyl-Al8C6 onto the quartz piezoelectric crystal also revealed that Y-type deposition was the favoured mode of deposition for both compounds. The maximum number of layers successfully deposited by the Y-type mode of deposition was twenty.

NOTES

25

SPECTROSCOPIC STUDIES OF HEMICY ANINE MONOLAYERS

Rob Hall (School of Chemistry, The University of Melbourne)

Hemicyanine compounds are highly polarizable, a characteristic which makes them, at first glance, suitable components in the production of non­linear optical devices. Much of the work on hemicyanines has focussed on the production of a large second harmonic signal from monolayers at the air-water interface, while a more complete understanding of the orientation of the chromophores has been somewhat neglected.

Absorption spectra of a docosyl derivative of the hemicyanine chromophore were measured at the air-water interface as a function of surface concentration. At low compression, a broad band is observed corresponding to a monomer-like species. With increasing surface concentration two new bands grow in concurrently at the expense of the monomer band. Deconvolution of the spectra shows that the two aggregate bands are produced by a single aggregate species. In terms of exciton theory, this corresponds to the aggregate geometry having two molecules per unit cell.

Over the past five years, the complexation of a polyion of opposite charge to the mooolayer at the air water interface has been employed in an attempt to increase stability. The polyion complexed hemicyanine monolayer exists only as the monomer al all surface concentrations, in contrast to the monomer-aggregate equilibrium observed on a pure water subphase. When the complexing agent is a monomeric sulfate, the aggregate is observed. Thus, the polymer disrupts the organized structure of the monolayer, preventing the formation of the aggregate.

NOTES

26

UL TR.A-MICRO BIOSENSORS

Sarah Gardiner (New Zealand Pastoral Agriculture Research Institute, Palmerston North)

A biosensor is an analytical device which use biological component/s to detect biological or chemical species in solution. Ultra-micro biosensors are characterised by having a sensing region or the order or I µm in diameter.

For the past several decades, microcapillary electrodes with tip diameters or less than 1 µm have been routinely used to measure the electrical potential or cells. More recently, these have been modified by filling the tip with hydrophobic solutions of ionophores to produce lijuid ion exchange microelectrodes capable of measuring pH, K+. Na+. Ca +. ci-. and NOr . A logical development would be the inclusion of enzymes at the tip of a microelectrode in order to measure organic compounds.

Our research is primarily intended to fabricate micro electrodes for use in cell physiology studies. Initially, micro pH electrodes were fabricated using an ionophore sensitive to hydrogen ion concentration. Derivatised poly(vinyl chloride) is used at the tip to provide mechanical stability. The electrode can then be modified by chemical bonding to attach an enzyme such as urease. The electrical potential of such an ultra-micro biosensor is dependent on the concentration of urea in solution.

NOTES

27

SURFACE STUDIES OF QUINHYDRONE pH SENSORS: FABRICATION & CHARAClERIZA TION

Christina Aquino-Binag (School of Chemistry. University or New South Wales)

A polymer-modified non-glass electrode was fabricated using quinhydrone (QH) in a poly(vinyl chloride) (PVC) matrix supported by a low porosity carbon rod. The electorde has a Nemstian response with slope of 34.1 ±? .3 mV/pH (25°C), a linear working range of pH 3 to 10 and an average response time or 5 to 7 minutes. Electrode stability was maintained over a period of 36 days without the need or pre-treatment prior to use or immersion in solution when not in use. X-ray photoelectron spectroscopy (XPS) was ued to probe the composition and surface characteristics of the electrode in attempt to understand the chemical basis of electrode performance. Angle resolved understand the chemical basis of electrode performance. Angle resolved XPS (ARXPS) showed that electrodes with a poor performance had an oxygen enhanced surface; presumably due to increased surface concentration of oxygen containing quinhydrone. This QH surface readilly oxidised when in contact with solution. Electrodes with a high performance had a chlorine enhanced surface, indicating a PVC-rich surface which served not only as a matrix, but as a protective layer for the quinhydrone. The comparison of electrochemical and electron spectroscopy data indicates that electrode composition and performance are closely related to fabrication techniques.

NOTES

28

VAPOUR DEPOSITION POLYMERIZATION OF POL YIMIDE

Than-Trong (School of Chemistry, University of NSW)

No Abstract received

NOTES

29

MISCIBLE INTERFACE STABILITY IN HELE-SHAW FLOWS

Eric Weisser (Department of Chemical Engineering, The University of Melbourne)

Viscous fingering is an interfacial phenomenon that occurs in all two phase displacement systems. It has become a large problem in secondary recovery processes in enhanced oil recovery ,and this provides the motivation for the current project.

It is well known that for Newtonian systems, in the absence of interf acial tension, ie miscible systems, that the viscosity ratio between the two fluids will control the degree or fingering in the displacement process. The addition of small amounts of polymer to either fluid can cause significantly different displacement patterns, due to the elastic behaviour of the non­Newtonian fluid.

A Hele-Shaw cell is used to examine the effects of changing the rheology on the displacement process. Preliminary results from these experiments will be presented.

NOTES

30

THIN IRON FILMS ON COPPER

Markus Borbach (School of Chemistry, University ofNSW)

Iron is widely used as a catalyst - the large scale industrial production of ammonia being a prime example. The catalytic efficiency of iron turns out to be highly sensitive to the state of the iron surface and single crystal studies reveal that the surface structure is also of high importance. At temperatures under 900°C iron is present in an fee structure, but it is possible to grow an bee iron film of some monolayers on a bee copper substrate by evaporation in ultra high vacuum. Iron and iron oxide films of different oxidation state have been grown on polycrystalline copper substrates. The parameters influencing the film growth, such as the evaporation rate, oxygen partial pressure and substrate temperature, are under investigation. Both polycrystalline and single crystal (100 face) copper substrates are being studied using X-ray Photoeletron Spectroscopy (XPS) and Low Energy Electron Diffraction (LEED).

.(\\~

\. ..._,

NOTES

\ - \ 0 CJ M.(.) r'\O \4-y""1")

l\ \-\ \} - (._Q""C-A, \c\. to~

:[c--e>n

0-~peh ._ \ \ ~

D~,~,~~ -) f=c...L--0_)

31

INTRINSIC STRESS AND GROWTH OF MAGNETRON SPUTIERED ALMS

Martin Puchert (School of Chemistry, University of NSW)

Intrinsic compressive stress is a widespread phenomenon in films deposit~ by ion beam deposition methods, such as sputtering. This stress can have significant influences on certin film properties such as film crystallinity,

~ chemical bonding, and film adhesion to the substrate. In this study, compressive stress in OC magnetron sputtered carbon films has been measured during the initial stages of growth, using ex-situ optical interferometry. The compressive stress is found to be anomalously large when the film thickness is between 40 nm and 85 nm, and decreases lo a plateau value of 1.5 GPa at greater thicknesses. This phenomenon is believed to be related to the transition from discontinuous to continuous film growth. X-ray phooloelectron spectroscopy (XPS) was used to monitor the change in carbon films, by using the native SiOz layer as a marker of exposed substrate regions. High magnification images taken with an atomic force microscope (AFM) show that disconnected carbon film growth is much more prevalent when deposited on Si with the native oxide layer left remaining, as opposed to a sputter-cleaned Si substrate.

~~\\~~ I ,--\-5~ !!-

(.OJ.I'---\~~ ArY\

\-C.,~o \ \) e.. ~'>

~~~

~bj~

NOTES

32

DIRECT MEASUREMENT OF SURFACE FORCES IMPORT ANT IN THE FOULING OF MICROFIL TRA TION MEMBRANES

Laurence Meagher (Department of Chemistry, ANU)

The fouling of membrane filters by particulate matter is an important industrial problem. This study is an investigation of the influence of surface forces on the fouling mechanisms. Examples of direct force measurements made using a modified Atomic Force Microscope will be presented that demonstrate that in some cases non-DL VO interactions, such as the hydrophobic interaction, dominate the total force curve. Some preliminary force measurements between SiO2 particles and polypropylene surfaces in NaCl solutions will also be presented.

NOTES

33

SYNTHESIS AND ACTION OF NOVEL ORGANIC COLLECTORS FOR THE FLOTATION OF ZIRCON

Mick Bjelopavlic (School of Chemical Technology, University of South Australia)

This presentation describes the progress made toward the synthesis of a series of novel organic collectors designed specifically for the flotation of zircon. Also mentioned are some preliminary flotation results, as well as an overview of the general principles of the action of surfactants on surfaces.

To date, a series of alkyl hydroxamic acids, mono-alkyl phosphates and alkyl esters of maleic acid of varying alkyl chain length have been synthesized. Flotation tests using the alkyl hydroxamic acids are currently underway on zircon sands from Tiwest.

The syntheses of a series of other organic collectors is ongoing, and it is hoped that these can soon be successfully produced and their surfactant properties assessed in due course.

NOTES

34

FORMATION OF LA TEX PARTICLES

Kate Drummond (Chemistry Department, Monash University)

The formation of latex particles during the aqueous free radical polymerization of acrylonitrile was studied. The study was conducted by using a tubular flow reactor to collect samples both before and after the precipitation event which marks the onset of rapid polymerization. The colloidal nature of the particles was characterized in terms of the particle morphology, the latex particle size distribution and the zeta potential of the latex particles.

At the very beginning, polymer particles (-5nm diameter) made up of single molecules are fomted. Prior to the precipitation event these primary particles aggregate to form the latex particles. It has been found that there is a rapid growth of particles before the precipitation event. The results also indicate that, during this stage, the latex particles grow by homo-aggregation of the primary particles. Following the onset of rapid polymerisation there is a change in the particle growth rate. This corresponds lo a change in the mechanism of particle growth. The decrease in the growth rate of the latex particles and subsequent onset of rapid polymerization indicates that surface polymerization then predominates. It has been found that hetero­aggregation also occurs to some extent.

NOTES

¥o~4t>\c..v-- r-s--t+J~ -, ~.\-~"~ c.,\\ 1.,-'%. t., \>L.)ll •

r='~~i.~

Sp:::> i' o\.,~o~-e.dc..

5>L \\ 0 ~ ~j :f ~A..\ \o ~

f re. c..\p'd ~ jO(\ 7 . .

-~s- -7 -,~ 77

~ t)~ i f4-l \te-\.c:_ ":)·5r; "' o-A \· \ ~ c.}'\(_

SUCROSE BASED SURFACTANTS - STRUCTURE AND BIODEGRADABILITY.

Irene Baker (CSIRO, Division of Chemicals and Polymers)

The biodegradation of some sugar based surfactants was studied. Using the Australian Standard method (Australian Standard 1792 - 1976) after modification to enable delermination of ultimate as well as primary degradation.

Sucrose monolaurate and raffinose monolaurate showed 100% ultimate degradation after 23 days, while sucrose monosulfolaurate and raffinose monosulfolaurate showed 75% and 80% respectively.

Elucidation of relationships between slructure and biodegradability, for this class of surfactants, will be of use in the design of environmentally acceptable surfactants for specific applications.

NOTES

36

chool of Chemical Technology, Un~rsity of South

Substituted naphthalenes are ass of compounds which appear to offer promise as selective c ctors in the depression of carbonaceous materials. The main obj · e ofthis study is to therefore investigate possible methods for in ing various chain length alkyl groups into the substituted

thalene ring and to synthesizediff erent types of naphthalene derivatives with functional groups containing C,N and 0. We decided initially to examine the synthesis of alkyl-substituted naphthylamines · rating selectivity of position of substitution, variation o of alkyl group and reaction conditions for good yields. me for the synthesis of a series of substituted 1-naphthylami been proved successful and satisfactory reaction conditions ~~lro(]Kl yields were found.

NOTES

37

SYNTHESIS OF MICROGEL PARTICLES AND THEIR CHARACTERISATION BY GEL PERMEATION CHROMATOGRAPHY (GPC) WITII ONLINE MULTI ANGLE LASER LIGHT SCATTERING (MALLS)- AND REFRACTIVE INDEX (RI) DETECTION.

Ludger Pille (School of Chemistry, University of Melbourne)

Microgel particles are highly cross linked polymer molecules which, contrary to conventional macrogel, are soluble.

The synthesis of microgel particles by anionic dispersion polymerization will be reported. Also, the characterisation of these particles by gel penneation chromatography with on line Multi Angle Laser Lightscattering - and Refractive Index detection will be described.

NOTES

38

SEPARATION BEHAVIOUR OF MICRON SIZED PARTICLES IN STERIC/HYPERLA YER FLOW FIELD-FLOW FRACTIONATION.

Deirdre Murphy (Department of Chemistry, Monash University)

Flow field-flow fractionation (FFFF) is a memberof the recently developed family of FFF separation techniques. The flow FFF technique has great versatility in the range of sizes it is capable of fractionating ie. from a few thousand Dalton to large 100 µm sired particles. This flexibility is attributed to the different separation processes occurring within the channel of the FFF apparatus. A cross flow of carrier drives the particles to the accumulation wall. Large particles with a smaller diffusion coefficient will attain a position close to the channel wall and smaller particles with more diffusivity will equilibrate nearer the middle of the channel. A second carrier flow along the channel length then effects separation.

When particles are very large they are driven to the wall as described above, but because their larger dimensions protrudes into the faster flowing streamlines, they are eluted (aster than they would be expected to if eluted by the normal mechanism. This mechanism of separation is described as the steric process. An added complication in this process occurs when channel flow rates are increased. Spherical materials such as polystyrene beads, colloidal silica, chromatographic silica supports, pollens and spores have been successfully characterised by steric/hyperlayer flow FFF.

The behaviour of prolate ellipsoids (squashed polystyrene latex bead standards) have been investigated under a range of experimental conditions. The effect of lift forces on these ellipsoids are explored and the possible transport mechanisms examined.

NOTES

39

AN ELECTROCHEMICAL STUDY WITH THE ATOMIC FORCE MICROSCOPE

Erica Wanless (Department or Applied Mathematics. ANU)

A special cell has been designed for electrochemical use with the Atomic Force Microscope. The motivation behind the design was to observe growth processes on the microscopic level. Our aim is to probe the diffusive and electrostatic fields and the geometry of a growing electrode deposit. Some preliminary measurements will be presented.

NOTES

40

FORMATION OF GOLD SOLS USING UL 1RASOUND

Stephen Au Yeung (School of Chemistry, University of Melbourne) ·

The fonnation of colloidal gold particles of diameter less than 10nm has been achieved by the irradiation of aqueous HAuCLi solution with 20kHz ultrasound. The particle size and efficiency of the particle formation is highly dependent on the presence of alcohol, its type and concentration, in the solutions. It has been established that alkyl hydroxy radicals are formed at the interface of microbubbles produced by the sound waves. These

radicals reduce AuC14 ·• leading to the formation of colloidal gold.

NOTES

41

11-IE DYNAMIC MOBILITY OF A SUSPENSION OF INTERACTING PARTICLES

Paul Rider (School of Chemistry, The University of Sydney)

When an alternating electric field is applied to a colloid the particles oscillate at a velocity proportional to the applied field strength. The complex constant of proportionality is termed the dynamic mobility. Although this quantity can now be measured at frequencies of up to 10MHz in suspensions of arbitrary concentration, the theory for relating these measurements to the size and charge of the particles is limited to suspensions in which it can be assumed that particles move without interacting. Results will be presented for the dynamic mobility of a suspension in which interactions between pairs of particles are dominant. The contributions to the dynamic mobility from particle interactions, back.flow of fluid and electric field screening will be compared. The implications of these results for size and charge determination using electroacoustic measurements will be discussed, as will the mathematical techniques used in the calculation.

NOTES

42

f

ELECTROACOUSTIC STUDIES OF UNSTABLE SUSPENSIONS

Melanie Carasso (School of Chemistry, Sydney University)

The AcoustoSizer is a new device for measuring the size and zeta potential of particles in non-dilute colloids. In this study the AcoustoSizer was used to correlate the filterability of coagulated suspensions with their colloidal properties. With unstable suspensions we found that particles deposit on the AcoustoSizerelectrodes, and this can influence the signal. Attempts to prevent this deposition are also described.

NOTES

43

...

MASS SPECTROMETRY OF SURFACES

Paul Pigram (School of Chemistry, University of NSW)

No Abstract received

NOTES

44

MULTICOMPONENT INTERACTIONS IN PROTEIN ELECI'ROPHORESIS

Andrea O'Connor (Department of Chemical Engineering, The University of Melbourne)

Electrophoresis isa technique extensively used and understood in analytical­scale purifications and separations. Free flow electrophoresis has significant potential to be scaled up for economical industrial separations, but the understanding of this process is limited. There is no existing method to predict the efficiency of separation, largely because of a lack of quantitative information about the effects of system conditions and protein - protein interactions. Experiments involving the electrophoresis of proteins through filtration membranes have been performed and results will be presented. The analysis of the effect of system conditions and interactions of proteins with each other and with the membranes will be discussed.

NOTES

~&,) f>~f-\ w M-c~\or~c: "::)

45

l '

PHYSICAL CHARACTERIZATION, QUANTIFICATION AND BIOMASS DETERMINATION OF BACTERIA USING SEDIMENTATION AELD-fLOW FRACTIONATION

Reshmi Sharma (Department of Chemistry, Monash University)

Cell counts and biomass estimates are important measures of microbial activity and production in aquatic ecosystems, but the techniques currently used are often tedious and time consuming. New methods such as image analysis or flow cytometry have been developed but can be expensive and may be limited to cell sizes larger than those found in most aquatic ecosystems.

Sedimentation field-flow fractionation (SdFFF) offers a rapid method for characterizing the physical properties (size and density) and quantifying the cell concentration and biomass of bacteria. Several isolates of cultured bacteria were studied with respect to their buoyant density and size distribution. After separation by SdFFF the cell sizes in various fractions were measured by an independent method (epifluorescence microscopy). Combining this estimate of cell volume with the SdFFF retention time enables the cell density to be calculated. The buoyant density of pure cultures ranged from 1.016 to 1.14 gcm-3, however, within a given species of bacteria, the cell density was almost independent of cell size. Using the average cell density determined by this method, the size distribution of the bacteria population can be calculated from the fractograms.

NOTES

46

THE ELECTROPHORETIC MOBILITY OF A SPHERICAL COLLOIDAL PARTICLE IN AN OSCILLATING ELECTRIC FIELD.

Christine Mangelsdorf (Department of Mathematics, The University of Melbourne)

The theory developed by De Lacey & White[J .Chem.Soc., Faraday Trans. 2, 1981,(77),2007] to calculate the electrophoretic mobility of a solid, spherical colloidal particle subjected to an oscillating electric field is modified to include the inertial terms in the Navier-Stoke's and colloidal particle force balance equations. These equations are solved numerically throughout the range of zeta potential, frequency, particle size and electrolyte concentration and are also solved analytically for low zeta potential. The numerical results are compared with the De Lacey & White model, the low zeta potential formula and the thin double layer result of O'Brien (J .Fluid Mech.,1988,(190),7 I].

NOTES

47

THE SURFACE PROPERTIES OF ZIRCONIA IN AQUEOUS SOLlITIONS

Mirjana Prica (School of Chemistry, The University of Melbourne)

The interfacial properties of zirconia in aqueous solutions will be discussed. Electrokinetic, charge titration and tritium-exchange data will be presented for three samples of zirconia which have been calcined at 450, 650 and

, 850°C. The peculiar behaviour of the 850°C zirconia sample is attributed to the dehydrated nature of the surface caused by the high calcination temperature. A model is proposed to explain these results.

NOTES

48

,._

FLOTATION OF ZIRCON AND ADSORPTION STUDIES IN THE PRESENCE OF SODIUM ALKYLAMINE BIS­METHYLENEPHOSPHONATE

Minghua Mao (School of Chemical Technology, University of South Australia)

Flotation of zircon in a modified Hallimond tube in the presence of sodium alkylamine bis-methylenephosphonate has been completed. Conditioning time, pH, Eh, collector concentration have been examined for their influence on the flotation behaviour of zircon. At pH around 3, best flotation results are received from the point of selectivity and recovery. The critical flotation concentration of all tested Briquest reagents is of the order 2 x 10-7 M. Carbon chain length has significant influence. The flotation of zircon is a n > I order kinetics process.

The adsorption of sodium alkylamine bis-methylenephosphonate onto zircon was investigated. FTIR spectra show that chelating compounds are fonned between the collector and zircon surface. The modelling of adsorption data shows that the adsorption isothenn falls into Langmuir adsorption type.

NOTES

2~~~~

49

HETEROCOAGULATION

David Atkins (Department of Chemistry, ANU)

Surface forces between zinc sulphide and mica substrates in aqueous solutions were measured for the first time using a modified atomic force microscope. The results exhibit an electrostatic repulsion regulated towards maintaining constant surface charge. To allow a detailed theoretical analysis of these results, the Hamaker constants for ZnS interacting with itself and mica, both across water were calculated.

Experiments were also perfonned to test the constant potential interaction in the more favourable case of an amphoteric substrate near its isoelectric point. Whilst not fully conclusive, the results appear to support our hypothesis that charge reversal is not exhibited during interaction.

We hypothesise that for heterogeneous interactions, the charge reversal at the surface with lower surface potential, implicit in the theoretical model, is unphysical and will not occur. This has implications for the manner in which DL VO theory is used to explain surface force data, as well as for the origin of the attraction between precursor particles in the emulsion polymerisation process.

NOTES

50

DYNAMIC MEASUREMENT OF MODEL DISPERSIONS

Nhol Kao (Department of Chemical and Metallurgical Engineering, RMIT)

In order to investigate the rheological behaviour of model polystyrene latex-gelatin-additive dispersions, studies on dynamic properties - viscosity (n'), storage (G') and loss (G") moduli-of the dispersions as a function of temperature, particle size, polystyrene solid concentration, gelatin concentration and concentration of additives ( salt and surfactant) have been carried out.

All experimental investigations (steady and oscillatory measurements) have been performed using the controlled stress Carri-Med CSLlOO rheometer. Oscillatory measurement is a useful tool for examination of the fundamental properties of viscoelastic materials (that is, any materials consisting of both a viscous component and an elastic component}, so that a better understanding can be achieved and applied to improve the quality of existing products. The major parameters which strongly influence the viscoelasticity of the dispersions were found to include the small polystyrene particle diameter and the high concentrations of polystyrene solid and gelatin solutions.

NOTES

51

ISSUES IN MONTE CARLO SIMULATION

Lorraine S taehr (La Trobe University College of Northern Victoria, Bendigo)

1be project involves Monte Carlo simulation and the graphical representation of adsorption processes. Preliminary work has been done in two areas. One aspect is the graphical representation of the adsorbing particles and associated data structures. Graphical representation has been implemented using the X Window System. The other aspect is the possible effect of using different pseudo random number generators. The simulation of a two dimensional hard disk fluid has been investigated using different pseudo random number generators.

NOTES

52

BEHAVIOUR OF SOLUBLE COAL COMPONENTS

Mr Sung (Department of Chemistry, Swinburne University)

It has been found previously that humic acids behave in solution at low concentration as polyelectrolytes, ie, the reduced viscosity increases markedly with decreasing sodium humate concentration. This behaviourof polyelectrolytes indicates an increased intramolecularelectrostatic repulsion and coil expansion with increased electrolyte dissociation of the poly-ion brought about by dilution. Here we focus on the coulombic interaction between coal components originating from the ionisable functional groups, predominating in lower rank coals. By selecting a conventional counterion as the base (sodium hydroxide) and a base capable of extensive hydrogen bonding (ammonium hydroxide), neutralisation and hydrogen bonding is probed in such processes as molecular conformation, aggregation to yield clusters and dissolution. This study reflects upon the molecular associations that lead to clusters capable of producing such behaviour.

NOTES

53

'

/'I PtoS> THE FLOT A TION OF HELL YER GALENA

Christopher Greet (School of Chemical Technology, University of South Australia)

A description of where Aberfoy le' s Hellyer operation is located, and a brief account of the problems associated with Pb flotation are given. Part of the investigation has centred on determining if there are any major difficulties between the galena that floats and that which does not. The starting point for this study has been an examination and comparison, using SEM and XPS techniques, of Pb rougher concentrate and tail streams. Samples of these pulp streams were sized, and the size fractions examined using SEM to determine variations in particle shape, mineral form and associations. XPS analysis provided information about the species on the surface of the minerals. Results are discussed, along with problems associated with this investigative work. Some indication of the future direction of the research has also been described.

NOTES

54

MODELLING PRESSURISED UL TRAFIL TRA TION WITH COLLOIDAL INTERACTIONS

Warwick Holt (Department of Mathematics, The University of Melbourne)

Steady-state pressurised ultrafiltration is a common method of cleaning colloids, in particular latex colloids. At significant volume fraction, it is not clear what effect inter-particle interactions will have upon the concentration of the filtrate. At steady-state, there will be a non-unifonn colloid distribution within the ultrafiltration apparatus. By detennining the osmotic pressure distribution, we can obtain the equivalent equilibrium state corresponding to a colloidal system prepared by this method. Simulation is being perfonned via computational methods.

NOTES

~~ (U-u \'.\ t~cJ~*"'.J Scd .. \ 1°'1~?

f~ no\ c=-AAy Gmil-(\0"'-V J--~

t>u.T c\ ~~ ~ .

CL

CXX)c)O~~Q V

c_f

55

DISSOLUTION OF SULFIDES IN AQUEOUS SOLUTIONS

Joan Thomas (School of Chemical Technology, University of South Australia)

There is interest in the major influences and mechanisms for the dissolution of sulphides in aqueous solution under varying conditions of pH and Eh. It is proposed that the formation of iron(III) hydroxide is a controlling factor in the dissolution of iron(Il) sulfides. Conditions which prevent the accumulation of Fe(OH)3 are favourable for dissolution.

Calculations on data for the dissolution of pyrrhotite in perchloric acid revealed interesting features. Less acidic conditions cause a slowing of the initial rate which in tum, allows enough time to elapse for a passivation effect. The rates of reaction for both the earlier and latter stages are temperature sensitive. Calculation of the activation energies gave values in the region for "reaction controlled" mechanisms with the value for the latter stage of the reaction being higher than the first This was surprising because a change to a diffusion controlled mechanism had been postulated. The experiments also showed that when 1 M perchloric acid was used, rapid dissolution occurred at higher temperatures but an initial passivation of the surface occurs at lower temperatures.

It is proposed to investigate this early passivation and the mechanism by which it disappears, and to compare it with the passivation which occurs in the latter stages of dissolution. Further temperature and rate measurements will be done. Investigations of the pyrrhotite surface during formation and removal of the early passivating layer will be carried out.

NOTES

56

CALCULATION OF THE ELECfROST A TIC POTENTIAL AND FORCE BETWEEN IDENTICAL SPHERICAL COLLOIDAL PARTICLES -THE POISSON BOLTZMAN THEORY

Jim Stankovic (DepartmentofMalhematics, The University of Melbourne)

Results are presented for the double-layer force between identical spherical colloidal particles using the non linear Poisson-Boltzmann equation. Resulls for lhe cases where the particles inleract at constanl surface potential and constant surface charge are compared with results based on the Deryaguin approximation, the superposition and the corresponding linear problem.

NOTES

~)\- i(A /() + ' ""~cc..v---o.A- ~ ~ "l(C\ ~~ ,,.

57

LAMINAR FLOW OF DILUTE SOLUTIONS OF SEMI-RIGID ROD MOLECULES THROUGH AN ABRUPT TIJBULAR CONTRACTION

Mruk Zimsak (Department of Chemical Engineering, The University of Melbourne)

Dilute solutions of xanthan gum in wheat syrup were constructed. These solutions were characterized in tenns of shear viscosity, first nonnal stress difference, dynamic viscosity, storage modulus and loss modulus using an Rl9 Weissenberg Rheogoniometer. Streakline photography was used to observe the flow field of these solutions through an abrupt 4.4: l tubular contraction at a number of flow rates. The change in the flow field with increases in base solvent viscosity, concentration, and the introduction of shear thinning were observed. Comparison was then made with the flow fields observed for constant viscosity, flexible molecule polymer solutions (Boger fluids) and also to the flow fields observed and predicted for constant viscosity, semi-dilute suspensions of short glass fibres.

NOTES

58

THE EFFECT OF FLUID HYDRODYNAMICS ON DROPLET COALESCENCE

Trina Dreher (Department of Chemical Engineering, The University of Melbourne)

Droplet motion is of interest in many fields including fermentation, polymer processes, waste treatment and food processing.

Droplet coalescence is considered to be a lhree step process consisting of droplet approach and contact, interfacial liquid film drainage and droplet rupture, which is very rapid in comparison to the first two steps. The drop approach time is controlled by the hydrodynamics of the bulk liquid phase. The interfacial drainage rate is controlled by lhe hydrodynamics of the liquid film and is lhe controlling factor in lhe coalescence time of a droplet at an interface.

A number of experimental investigations on the effects of fluid properties on drop coalescence have been published, although little work has been conducted on lhe effects of interfacial rheological properties.

This paper briefly reviews lhe existing theories and models of coalescei:ice and proposes a framework for which to investigate the effects of rheological properties on drop coalescence at an interface.

NOTES

59

'

ORDERING OF SMALL PARTICLES UNDER OSMOTIC SlRESS

Olivier Spalla (Department of Applied Mathematics, ANU)

Nanometric particles of cerium oxide can be dispersed in water. The experimental equation of state of such dispersions have been measured using the method of osmotic compression. Structure of the dispersions have been detennined in parallel with X-ray scattering. We found that both the structure and the equation of state depend on the solvent conditions. In the case of purely electrolytic solvents the results can be interpreted in tenns of electrostatic interactions. In the presence of an attraction induced by a polymer a transition from an isotropic ordering to an anisotropic ordering is observed.

NOTES

60

THE RHEOLOGY OF TITANIUM DIOXIDE PIGMENT SUSPENSIONS

Petra Liddell (Department of Chemical Engineering, The University of Melbourne)

A knowledge of the rheology of titanium dioxide pigment suspensions and the variation with processing conditions is essential for optimum plant operation. The aim of this study is to investigate the influence of pH, solids concentration, particle size and process history on lhe rheological properties of Ti02 pigment suspensions. Four different Ti02 pigments were used for this study, supplied by Timlide Chemicals Pty Ltd. The results show that the rheology is extremely sensitive to both pH and solids concentration. The maximum viscosity was found to increase with decreasing particle size. Another important outcome of the investigation was the dependence of the rheology on process history. The "in-process" pigment exhibits a significantly greater suspension viscosity than the final products. This can be attributed to changes in surface area and porosity due to the filler type used in production (ie plate and frame or press belt) affects the rheology. sugges1ing that compression history is an important variable. Finally, the presence of a monolayercoating of organic additives on the pigment surface was shown to lower the suspension viscosity.

NOTES

61

'

ACOUSTIC INTERACTION ENERGY OF A THIN LA YER ON A SUBSTRATE.

James Gunning (Department of Mathematics, The University of Melbourne)

The interaction energy arising from elastic mechanical vibrations in a thin layer on top of a infinite substrate is derived for both solid and fluid layers. This energy is shown to scale with the speed of sound in the layer, as distinct

... to Van der Waals energies which scale with the speed of light, and thus we conclude that surface acoustic oscillations are unable to account for strong, long range interactions in colloidal systems.

NOTES

~ \.l . ¥._-:i½o f 'lr-61/J \c

~\~~DC

62

~ce-:S

D c\.~fe1td~

LA TIICE GAS S1UDIES OF POROUS MEDIA FLOW IN THREE DIMENSIONS

Xiadong Zhang (Department of Applied Mathematics, ANU)

The conductivity a of a fluid saturated porous medium is often related to its penneability k via empirical relations of the fonn Ll2( a/a0 ) where a0 is the fluid conductivity and I a characteristic length scale of the medium. Three characteristic. length scales have been widely reported in the literature; L, the ratio of pore volume to pore surface area, A defined by electrical conductivity measurements, and a diffusion-limited trapping length, ws. None is successful over the entire range of porosities and pore size distribution. In this paper we tesi the relevance of the various permeability estimation techniques for several model porous media in three dimensions utilizing lattice gas automata.

NOTES

63

..

THE BREAK-UP OF LAMINAR FLOW JETS

Robert Mun (Department of Chemical Engineering, University of Melbourne)

The break-up of liquid jets is of interest in many industrial applications. The primary question being; What factors directly affect the way in which the jet breaks up. Previously identified factors are swface tension, and viscosity. This study aims to quantify the effects of fluid elasticity ( visco­elastic and extensional behaviour), and the presence of colloidal material. As a first step, the results of previous workers are to be duplicated, but in a manner that will produce far more information than has been previously obtained.

NOTES

64

DIFFUSION IN DILUTE POLYMERIC LIQUIDS

Jane Wright (Department of Chemical Engineering, The University of Melbourne)

Diffusion in dilute polymer solutions is of interest to many areas including biological systems, physiological processes, polymerisation and waste treatment. A number of experimental investigations of diffusion through dilute polymeric solutions have been published. Dilute polymer solutions are generally shear thinning and often elastic and significant confusion exists in regard to non-Newtonian viscosity and elasticity effects on the diffusion coefficient. The influence of the rheology of the solvent system on the diffusion process will be presented. Particular emphasis will be placed on discussion of those rare diffusion measurements where both the kinematic and rheological properties have been carefully controlled. A framework in which to conduct such controlled measurements will be proposed.

NOTES

65

GROWTH OF COLLOIDAL CRYSTALS

Stuart Henderson (Department of Applied Physics, RMrD

Colloidal hard-spheres of polymethylmethacrylate (PMMA) suspended in a liquid are used to model atomic systems. Crystallization will occur at sufficienlly high densities, the disorder to order transition being driven by entropy alone. By index matching the suspending fluid with the PMMA

, particles, light scattering techniques can then be used to observe the growing crystals within the bulk of the sample. It has been found that crystal growth is heavilly influenced by the shear history of the system.

NOTES

66

BUBBLE/PARTICLE INTERACTION

David Hewitt (School of Chemical Technology, University of South Australia)

The mechanism of bubble/particle capture is central to a fundamental understanding of froth flotation. Successful capture involves bubble/ particle collision, attachment of the particle to the bubble, and the establishment of a stable bubble/particle aggregate. Experiments have been carried out using particles and bubbles of dimensions usually encountered in froth flotation allowing the collection efficiency to be detennined. Calculations using theoretical models for the collision and stability efficiencies pennitted the results to be interpreted in tenns of the bubble/ particle attachment efficiency. Models for the sliding time were used to calculate the induction times for the experimentally determined attachment efficiencies, which were measured for variation in particle size and hydrophobicity, bubble size and background electrolyte concentration. The results are discussed in terms of the significance of surface forces in bubble/particle attachment.

NOTES

67

DIRECT FORCE MEASUREMENTS BETWEEN TIO2 SURFACES

[an Larson (School of Chemistry, The University of Melbourne)

An Atomic Force Microscope was used to measure the total force of interaction between a TiO2 rutile colloid and a single rutile crystal. The forces were measured as a function of pH and electrolyte concentration.

The changes in potential and Debye-length with pH and salt concentration were found to agree with theory within experimental error. The measured forces were found to agree well with classical DLVO theory and thediff use­layer potentials compared well with zeta-potentials determined by electrophoretic measurements.

~ Calculations of the van der Waals interaction between two TiOz surfaces based on spectral data of rutile TiO2 have been made and a Hamaker constant of 6.1 x 10-201. detennined. Experimental results using the AFM support this theoretical value very well. · ,

NOTES

68

ne-n'l.\ec:\e.,, l --SURFACE PROPERTIES OF A TRIVALENT CAGE SURFACTANT INVESTIGATED USING ATOMIC FORCE AND CONFOCAL MICROSCOPY

Marilyn Karaman (Department of Applied Mathematics and Chemistry, ANU)

We have studied a unique trivalent cage surfactant which has significant biological activity in parasitic namatodes (in-vivo). This activity was investigated by the aid of a conf ~al microscope on sheep red blood cells allowing the mode of action to be studied at a cellular level. Direct force measurements were carried out using colloid probe Atomic Force Microscopy on adsorbed surfactant bilayers.

NOTES

69

'

THE INTERACTION OF MET AL ION HYDROLYSIS PRODUCTS WITH SULPHIDE MINERALS

Peter Clarke (School of Chemical Technology, University of South Australia)

This project has been concerned with the interaction of copper and zinc ions with sphalerite (ZnS). In order to separate zinc from copper sulphides, typical plant practice would see (for a mixture of sphalerite (ZnS) and chalcopyrite (CuFeS2)) addition of zinc to depress flotation of sphalerite, then collection with xanthate and flotation of the chalcopyrite. Activation of the remaining sphalerite with copper and collection with xanthate would then occur, prior to its notation.

Zinc depression of sphalerite is the process fo interest in this case. At high pH the depression process appears to be simply a "blanketing" of the mineral particles with Zn(OH)2. However, depression fo mineral flotation by zinc is selective for sphalerite, suggesting that additional mechanisms are at work.

Work to date has included both single and mixed mineral microflotation test, UV-Visible spectroscopy, AAS, microelectrophoresis, FT-IR and XPS to study the copper activation and zinc depression of sphalerite.

NOTES

70

BUBBLE COALESCENCE AND ELECTROLYTES

Vincent Craig (Department of Chemistry, ANU)

A range of electrolytes are shown to have surprising effects on bubble coalescence. Some inhibit coalescence. Others have no effect. The behaviour of electrolytes is embraced by empirically derived simple mathematical combining rules. The coalescence behaviour of a wide range of salts is predicted by these rules. No exceptions have yet been found.

A model is developed to explain the observed coalescence behaviour. The model incorporates the force balance acting between approaching bubbles. In water, the hydrophobic attraction dominates over the hydrodynamic repulsion. On addition of certain salts the hydrophobic attraction is reduced and the hydrodynamic repulsion becomes dominant. Under these conditions coalescence is prevented.

NOTES

71

MEASUREMENT OF THE FORCE BE1WEEN A SILICA R..AT AND SILICA SPHERE IN AQUEOUS CACL2 SOLUTIONS

Matthew Fielden (School of Chemical Technology, University of South Australia)

The Atomic Force Microscope (AFM) has been used to measure the force between a silica flat and an 8 µm silica sphere in CaCI2 solutions varying in concentration between 5 x 10-6 Mand 10-l M. The force/radius vs.

l ~ distance plots obtained agreed well with DL VO theory at long range (separations greater than 1/K = ... 5 nm), but at shorter range, the expected attractive van der Waals force was absent, and a strong repulsive force was present. The latter was attributed to hydration effects.

At concentrations higher than I M, a long range repulsive force (1/K = ... 30 nm) was apparent. Upon decreasing the scan rate from 5 Hz to I Hz, the repulsion was not observed. The apparent force at higher scan rates was thought due to viscous drag.

NOTES

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72

SURFACE STUDIES OF ADHESION FAILURE

Andrew Rider (School of Chemistry, University of NSW)

No Abstract received

NOTES

73

~ THE DEPOSITION OF STERICALLY STABILIZED LATEX ~ PARTICLES ONTO CLEAN SURFACES

Ge Li (School of Chemistry, University of Sydney) E -

The deposition of colloidal particles onto surfaces (collector) is importnat in a wide range oflechnologies: micro and ultrafiltration, paper making, dry cleaning, prosthetic implants, etc. The rotating disc technique has been widely used to detennine the deposition rate of spherical latex particles onto

" smooth collector surfaces. It is found experimentally that if the particles and the collector are opposite charged, the observed deposition rate is in close aggrement with predicted by the Levich theory of diffusion-controlled transport to a rotating disc. If, however, the latex particles and the collector surface are similarly charged, deposition is still observed while the DL VO theory predicts none. One explanation for this anomalous deposition is the presence of "hairs" on the mcxlel particle surfaces. This raises the little studied question of the deposition rate of the sterically stabilized colloidal particles. In the present work we used rotating disc technique to study the deposition of polystyrene latex particles stabilized by various water­soluble polymers onto various clean surfaces. The results and discussion will be presented.

NOTES

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74

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CHARACfERISA TION OF HYDRAULIC FRACTURING FLUIDS

David Power (Department of Chemical Engineering, The University of Melbourne)

Successful design of hydraulic fracturing treatments relies heavily on knowing the rheological characteristics of the fracturing fluids. One of the most common fracturing 0uids in use is a hydroxypropylguar solution. When crosslinked with metal ions the linear fluid lransforms into a gel. Determining the fluid properties is complicated due to the viscoelastic nature of the fluid and the gelled crosslinked state. The application of fluid properties to fracture design are discussed together with the parameters used to evaluate the fluid rheology. Methods used to model the flow system are also discussed. Characterising the fluids involves examining the linear and crosslinked states with and without solids present.

NOTES

75

THE EFFECT OF SURFACE MODIFICATION BY AN ORGANOSILANE ON THE ELECTROCHEMICAL AND RHEOLOGICAL PROPERTIES OF KAOLINlTE.

Belinda Braggs (School of Chemical Technology, University of South Australia)

A novel approach has been used to model the electrical double layer properties of kaolinite. The electrochemical and rheological properties of kaolinite before and after modification with chlorodimethy loctadecylsilane have been studied by electrophoretic mobility, swface charge titration and extrapolated yield stress measurements as a function of pH and ionic strength. The heteropolar model of kaolinite, which views the particles as having a pH-independent pennanent negative charge on the basal planes and a pH-dependent charge on the edges, has been used to model the data. The zeta potential and surf ace charge titration experimental data have been used simullaneously to calculate the acid and ion complex equilibrium constraints using a surface complex model of the oxide-solution interface. The parameters calculated for the modified kaolinite indicate that the silane has reacted with these pH-dependent hydroxyl groups on the edges causing a change in the acidity of these hydroxyl groups with a subsequent decrease in their ionization. lnfrared data provides evidence that the long chain hydrocarbon silane is held by strong bonding to the kaolinite surface as it remains attached after washing with cyclohexane, healing and dispersion in an aqueous environment.

NOTES

76

ELEMENTAL ANALYSIS OF COLLOIDAL PARTICLES BY SDFFF­CIP-MS

James Ranville (Water Studies Centre, Department of Chemistry. Monash University)

Inductively coupled plasma-mass spectrometry (ICP-MS) can be used to determine colloid elemental composition. Suspensions can be directly introduced into the plasma using slurry nebulization. The accuracy of the results depends upon the transport of particles to the torch and the efficiency of atomisation of particles in the plasma. Comparison of slurry versus conventional solution nebulization show good agreement, provided the particles are smaller than a few microns. Particle size plays a significant role in determining the behaviour of aquatic colloids and is an important parameter to determine. Substitution of slurry for solution nebulization allows direct coupling of ICP-MS to sedimentation field-flow fractionation (SdFFF). SdFFF is a high resolution, elution technique which separates particles based on bouyant mass. The particle fractogram, a plot of detector response versus elution volume is converted to a particle size distribution using FFF theory. The combination of SdFFF with slurry nebulization ICP­MS allows determination of the elemental composition across the entire particle size distribution. The accuracy of results obtained from direct solids analysis by SdFFF-ICP-MS is determined by comparison to ICP-MS analysis of total digestions of fractions collected from the SdFFF. This comparison allows more detiled quantitation of the size limits for which direct solid analysis by ICP-MS is accurate. SdFFF-ICP-MS shows potential as a powerful tool for environmental and colloid studies.

NOTES

77

ADSORBING COLLOID FLOTATION OF MERCURY(II)

Julie Angerosa (School of Chemistry, Swinburne University)

The removal of mercury(II) from industrial laden wastewaters (particularly containing high salt contents) was achieved using adsorbing colloid flotation (ACF). A mixed colloidal system of hydrated aluminium(III) and iron(III) oxides was employed together with a dual sodium laurate (NL) and sodium lauryl sulphate (NLS) surfactant system to effect efficient removal at near neautral pH. Adsorption experiments using an articifially prepared mercury waste were also performed. The adsorbing colloid flotation results were supported by the adsorption data and suggest that mercury(II) does not significantly adsorb as an anion, even under conditions where its dominant form is HgC42-.

NOTES

78

THE DEPRESSION OF TALC USING POLYMERIC ORGANIC MOLECULES

Gayle Morns (School of Chemical Technology, University of South Australia)

The natural hydrophobic properties of talc cause a reduction in the concentrate grade of sulphide minerals during flotation. Depressants are therefore added to the feed where they selectively adsotb onto the talc surface, rendering it hydrophilic and reducing talc flotation. A wide range of depressants have been used to depress silicate gangue minerals. There are nonnally chosen by empirical methods rather than on a scientific basis. Common depressants used are polysaccharides such as carboxymelhyl cellulose (CMC) and guar gum.

The degree of substitution (OS) or the carboxyl methyl groups has been shown to alter the polymeric depression action. The affinity of the polymer to either remain in solution or to adsorb onto the talc surf ace is governed by the degree of ionisation of the carboxyl methyl groups due to the polyelectrolyte characteristics. If the DS is too low the polymer will be either partially soluble or insoluble in water, but a low solution affinity favours adsorption onto the talc surface and therefore depression. If the DS is too high the polymer prefers to remain in solution therefore not adsorbing onto the talc surface. Other major influences governing depressant action are the molecular weight variation (degree of polymerisation) and molecular fonn of the polymers.

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MEASUREMENT OF THE SELECTIVE ADSORPTION OF IONS AT AN AIR/SURFACTANT SOLUTION INTERFACE

John Morgan (Department of Physical Chemistry, University of Sydney)

In a solution containing an ionic surfactant with severaldifferentcounterions, selective adsorption of ions al both the micellar and air/solution interface occurs. A numberof workers have been concerned with studying selectivity al the micellar interface, while the simpler air/solution interface has received little attention. We present a simple flotation technique which enables measurement of the selectivity of a cationic surfactant solution interface for competing ions, and discuss the dependence of selectivity on surface charge density, solution composition and temperature.

NOTES

80

THIONOCARBAMA TES · AS COLLECTORS FOR SULPHIDE MINERAL FLOT A TION

Gillian Fairthorne (School of Chemical Technology, University of South Australia)

Traditionally xanthates are employed as collectors in the selective flotation of sulphide minerals. Although powerful, they have disadvantages such as poor selectivity and ease of decomposition. Since the 1960's, thionocarbamates have emerged as alternative collectors demonstrating excellent stability and selectivity, particularly for copper minerals against the gangue minerals pyrite and pyrrhotite. As a result of the success of the dialkyl · homologue, isopropyl ethylthionocarbamate, the American Cyanamid Company have developed the alkoxy carbonylthionocarbamate. Varying the alkyl substituents to the functional group alters the physical properties of the molecule and hence the commercial applicability of the reagent.

A UV spectroscopic study of the solution properties of isopropyl ethyl and isobutyl ethoxycarbonyl thionocarbamates and subsequent determination of the pKa of the latter molecule is presented along with results of microflotation confirming the relative selectivity of each of the collectors compared with xanthate.

NOTES

81

'

ADSORPTION OF POL YPHOSPHA lES ONTOZIRCONIACOLLOIDS

Jenny Simmons (School of Chemistry, University of Melbourne)

There is currently great interest in producing high-performance advanced ceramic products based on controlled colloidal systems. The mechanical strength of the final product relies on a homogenous microstructure

, resulting from a well-dispersed ceramic slurry.

Inorganic dispersants off er greater durability than many of the organic deflocculants available. Polyphosphate dispersants are thought to act through electrostatic stabilization, however, their exact method of action is unclear.

The adsorption of polyphosphates onto colloidal zirconia (Zr02) particles has been studied as a function of chain length and pH. Adsorption isotherms have enabled the examination of the extent of adsorption and orientation of the polyphosphate at the oxide surface.

NOTES

82

ADSORBING COLLOID R..OTA TION OF AN ORGANIC DYE

David Lewis (School of Chemistry, Swinburne University)

Synthetic dyes can be a problem in waste water in that they are not read.illy degraded by the organisms in treatment works. A coloured effluent is produced that, apart from having a negative aesthetic impression, interferes with sunlight penetration into the water and impedes the growth of aquatic organisms.

An adsorptive colloid flotation (ACF) system is being developed to concentrate a crude industrial dye, Remazol Brilliant Blue R (RBB R) from a wastewater model. Our adsorption studies show that RBB R is readilly adsorbed onto hydrated oxide precipitates of both Al and Fe. Up to 100% of a 500ppm solution is adsorbed onto (a) aluminium(III) oxide when a250 ppm solution of A13+ is precipitated and (b) iron(IIO oxide when a 1000 ppm solution of Fe3+ is precipitated.

Adsorption isotherms show Langmurian behaviour. Up to 4500 mg RBB R per g A13+ is adsorbed at pH4.5. and up to 1000 mg RBB R per g Fe3+ is adsorbed at pH 4.0.

Sodium dodecyl"suphate (SOS) is the collector/frother currently being studied. Up to I 0% of dye is displaced from aluminium oxide by 150 ppm SOS in a system of 400 ppm RBB R/100 ppm At3+ over a pH range of 4.5 lo 6.5. This displacement is reduced to negligible levels when the Al3+ concentration is doubled.

NOTES

83

'

THE SURFACE CHEMISTRY AND FLOTATION BEHAVIOUR OF NICKEL SULPHIDE MINERALS

Michael Pietrobon (School of Chemical Technology, University of South Australia)

In general the study of sulphide minerals in the past has focussed on copper, lead and zinc sulphides as well as the major iron sulphide gangue minerals. There is a distinct lack of literature describing the fundamental properties of nickel sulphide minerals and their interactions with associated iron sulphides. Much of the work on nickel sulphides has been carried out in Canada and USSR which, in most cases, has involved the separation of copper sulphide minerals as well. However in Australian deposits the only mineral values present are the nickel sulphides, mainly pentlandite ((Ni,Fe)9Sg) and violarite (Ni2FeS4) with gangue iron sulphides consisting of pyrrhotite (FeS in several fonns) and pyrite (FeS2). The major fonn of non-sulphide gangue minerals present are serpentines (Magnesium hydroxide and silicate mixtures).

Nearly all Australian nickel sulphide deposits exist in a belt in Central­Western Australia. The AMIRA P260A project includes several of these operations and therefore provides a unique opportunity to study and compare differences in the processing of ore which has a similar geological genesis and yet has different processing problems. Specific case studies will be presented.

NOTES

84

MODELLING THE EFFECT OF TEMPERA 11JRE ON ADSORPTION

Anthony Natoli (La Trobe University College of Northern Victoria, Bendigo)

The adsorption of copper and lead onto goethite, alumina, kaolin and silica has been studied as a function of temperature in an attempt to better understand the influence of the substrate on adsorption. These results have now been analysed using four relatively simple adsorption models. two assuming only mono layer adsorption and two allowing for the formation of multilayers.

The two-site Langmuir model and the surface precipitation model of Farley, Dzombak and Morel, one a monolayer and the other a multilayer model, both provide acceptable fits to the experimental data. The adsorption constants generated by these models for different substrates and temperatures will be presented and discussed. Thermodynamic parameters foradsorption onto the different substrates can be derived from the variation of the apparent equilibrium constants with temperature.

NOTES

85

HEAVY MET AL ADSORPTION AND COPRECIPIT A TION

Russell Crawford (Department of Chemistry, Swinburne University)

The removal of all combinations of aqueous metal ions Cr(III), Ni(II) and Zn(II) using amorphous iron(III) oxide, and of aqueous Ni(II) and Zn(II) using amorphous chromium(III) oxide u the adsorbing or coprecipitating colloid has been measured and modelled using theJames-HeaJy model for

~ metal ion adsorption.

The results for the adsorption and the coprecipitation of single metals have been compared. In all systems, coprecipitation is more efficient than adsorption although in the case of Zn(II) removal by amorphous iron0II) oxide the difference was minimal. The contributions of the chemical free energy of adsorption to the overall adsorption free energy changes have been determined and found to be; greater for coprecipitation than for adsorption, greater for Zn(II) than for Ni0I) and greater for hydrated amorphous chromium(III) oxide than for hydrated amo.rphous iron(III) oxide.

NOTES

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