THE APPLICATIONS OF NANOFIBERS IN

WATER TREATMENT

Marelize Botes15 March 2010

• Contaminated drinking water - main cause of diseases in development countries.

• 1.1 billion people do not have access to safe water (WHO, 2004). • The importance of water disinfection and microbial control cannot be

overstated.

Water quality problems• Urban/Industrial effluent

• Acidic atmospheric deposits• Groundwater contamination

• Agricultural chemicals• Excessive sediment

• Metals (mining)• Radioactivity

• Salinity

• Chemical disinfectants and membrane-based water filtration systems control microbial pathogens.

• Harmful DBP’s and ↑resistant pathogens

• 2 significant obstacles in filtration are

Biofouling and virus penetration

The accumulation of microorganisms such as bacteria, fungi and algae on the membrane surfaces, with the subsequent formation of harmful biofilms and operational problems.

• Membrane permeability and membrane lifetime are reduced and energy costs are increased.

• High cost involved in controlling membrane biofouling and subsequently buying new membranes.

• Water loss and quality deterioration associated with aging distribution networks and the increasing cost to transport water.

• Increasing need for alternative water sources and wastewater reuse for water shortage problems.

• Urgent need for decentralized/point-of-use water treatment and reuse systems.

Potential solution = nanofibrous filter media

•High surface to volume•Low basis weight•High permeability•Small pore size

→ Remove unwanted particles smaller than 0.3 µm

Styrene dimethyl aminopropyl maleimide

Human hair vs nanofiber

• The first patent was published in the USA. • Filters of Petryanov was kept top secret in

Russia.• Were used after the Second World War to

protect the environment from nuclear-active aerosol release.

• Production gained momentum in 1980 in America and only started in the 1990s in Europe.

• Currently more than 20 enterprises worldwide.

S.N. Enterprises Country

1 Donaldson Company Inc. USA

2 Espin Technologies Inc. USA

3 KX Industries USA

4 Ahlstrom Corporation Finland

5 Hollingsworth Co. Ltd. USA

6 US Global Nanospace USA

7 Finetex Technology S. Korea

8 Helsa-automotive Germany

9 Nanotechnics Co. Ltd. S. Korea

10 Teijin Fibers Ltd. Japan

11 Toray Japan

S.N. Enterprises Country

12 Japan Vilene Company Ltd. Japan

13 Nanoval GmbH & Co. KG Germany

14 Hills Inc. USA

15 Nonwoven Technologies Inc. USA

16 Emergency Filtration products, Inc. USA

17 Elmarco Czech Republic

18 Hohns Manville Sales GmbH Germany

19 Nanofiber Future Technologies Corp Canada

20 Esfil Tehno Republic of Estonia

Polymer Solvent Concentration

Polyurethane (PU) Dimethyl formamide 10 wt %

Polycarboate (PC) Dichloro-methane

Dimethylformamide:

tetrahydrofuran (1:1)

15 wt %

20 wt %

Polylactic acid (PLA) Dichloromethane 5 wt %

Polyethylene oxide (PEO) Isopropyle alcohol and water 10 wt %

Polyvinylcarbazole Dichlormethane 7.5 wt %

Polystyrene Tetrahydrofuran 15 wt %

Polyamide (PA) Dimethylacctamide Not available

Cellulose acetate (CA) Acetone, acetic acid 17 %

Electrospinning

Negatively charged Target plate

Anode

Pipette with liquid polymer

Polymer droplet forming Taylor cone

High voltage power source

Cathode

Charged jet fiber Nanofibers collecting on plate

Copper wire

Small pore sizes, high specific surface areas and high porosity ↓

3 uses in water treatment

Separate solid impurities from the

liquid phase ↓

Filtration

Selective absorption/Adsorption

↓Affinity

membranes

Neutralise or decompose impurities

↓Reactive

membranes

Current Nanoscale applications in Water

Nano-sorbtion

Reactive membranes

• Functionalization by spinning blends of specific polymers

• Coating of fibers• Inclusion of functional components

such as antimicrobial nanoparticles

nanobiocidesMetal and metal oxides e.g. nAg, ZnO, CuO, TiO2

Engineered/syn-thesized nanoparticles such as fullerenes e.g. nanomagnetite (nC60) and carbon nanotubes

Natural antimicrobial substances e.g. antimicrobial peptides and chitosan

• Silver nanoparticles is considered to be the most toxic element to microorganisms: Ag >Hg >Cu >Cd >Cr >Pb >Co >Au >Zn >Fe >Mn >Mo >Sn

• considered an alternative to antibiotics.

• Antimicrobial filters, wound dressing material, water disinfection, sensors, air filtration

PAN fibers with 5 wt% AgNO3 forming silver nanoparticles on fiber surface with lysed S.aureus

Neat PAN fibers with in tact S.aureus

IVIS imaging of PAN fibers with or without 5%wt AgNO3

Pseudomonas aeruginosa

Escherichia coli

Staphylococcus aureus

• Zinc oxide (ZnO) nanoparticles have strong antimicrobial activity.

• Penetrate the bacterial cell envelope and disorganize the cell membrane.

• Applicated in pharmaceutical products and in surface coatings to prevent biofilm.

• Applications in water treatment is questioned as it is highly soluble in water increasing sensitivity of aquatic organisms towards ZnO.

• Copper oxide nanoparticles

• Titanium dioxide kills bacteria and viruses.

• Produce hydroxyl free radicals and peroxide formed under UV-A irradiation via oxidative and reductive pathways, respectively.

• TiO2 is stable in water and cost effective and can therefore be successfully incorporated in thin films or membrane filters for water filtration.

• Fullerenes (C60)• Carbon nanotubes should

be immobilized on a reactor surface or polymer matrix. Applicated in the prevention of biofilm formation in water filtration membranes.

• High cost involved and potential toxicity may hamper the use of carbon nanotubes in water filtration.

• NanoCeram® cartridges

• Natural antimicrobial substances – antimicrobial peptides and chitosan

• Chitosan nanoparticles show potential in drinking water disinfection applications such as antimicrobial agents in membranes, sponges and surface coatings

Two significant challenges in the long term are apparent.

1) the loss of antimicrobial or antiviral activity

• The cost involved and the impact on human health and environment.

• safety of escaped nanobiocides is not proved yet.

• Nanobiocides can also be turned into harmful chemicals when exposed to chlorine and UV.

2) Bacteria may become resistant towards the nanobiocides.

• Solutions

→ Improve fixation techniques by concentrating the nanobiocides closer to the surface of the membrane.

→ Encapsulation in a polymer matrix to decrease the release rate.

→ Modify the polymeric surfaces

Conclusions• Nanofibers show potential in water treatment

processes.• Reactive membranes may be the solution for

high-performance, small-scale/point-of-use systems.

→Increase robustness of water supply networks

and water systems not connected to a central network.

→Emergency response following catastrophic events.

Thank you for your attention