by Prof. Volodymyr V. Tarabara
The last two decades have seen membrane-based separation established as a family
of broadly accepted technologies that complement and often replace traditional
water treatment unit processes such as granular media filtration, chemical precipitation
and softening. Membranes processes such as microfiltration, ultrafiltration,
nanofiltration, and reverse osmosis, can be used to remove a diverse range of
pollutants from a variety of source waters. As of 2008, the membrane industry
in U.S. alone is $2.9 billion and growing.
The commercial success of membrane technologies is grounded in the continuous
innovation in the areas of membrane materials and processes. Recent developments
in the materials science of membranes have been fueled in large part by advances
in nanotechnology. Membranes with improved permeability, selectivity, and
resistance to fouling have been developed using newly available nanomaterials.
Functional nanomaterials have been used to synergistically combine separation
and additional functions and prepare more efficient membranes with a smaller
environmental footprint. Examples of nanomaterial-enabled membranes include:
i) membranes prepared from nanomaterials (e.g., ceramic membranes that have
been traditionally prepared from inorganic materials such as TiO2,
ZrO2, Al2O3, etc.1
but also the novel class of membranes prepared from carbon nanomaterials such as
ii) membranes prepared by
nanocomposite membranes (e.g., using TiO26-8, Ag09-11,
and SiO214-16, NaA zeolite17 as inorganic fillers);
iv) membrane reactors with
functional nanoparticles (e.g., Fe/Ni18-20,
Fe/Pd20,21, Ag022, gold23, zero-valent
Our NSF-sponsored research project “Partnership for International
Research and Education: New generation synthetic membranes - Nanotechnology
for drinking water safety” is an example of a large interdisciplinary of
effort focused on the development of new nanotechnology-enabled membrane processes
and technologies. The Partnership is on the design of nanostructured membranes
and addresses fundamental nanomaterials chemistry and materials science as applied
to water quality technologies. The project is a joint effort between a number
of research groups in the United States and abroad. An example PIRE project is our recent
study on the design of biofouling resistant silver-polysulfone composite membranes.
In this work, the nanocomposite membranes were synthesized by incorporating
silver nanoparticles into the polymer matrix of a membrane.
Inhibition of biofilm growth on the surface of Ag
The particles were either synthesized ex-situ and then added to the casting
solution as organosol or produced in the casting solution via in-situ reduction
of ionic silver by the polymer solvent. We have shown that the antibacterial
capacity due to the gradual release of ionic silver by the prepared
nanocomposites can be effective in reducing intrapore biofouling in
nanocomposite membranes of a wide range of porosities. Such nanocomposites could
also be used as materials for macroporous membrane spacers to inhibit the
biofilm growth on downstream membrane surfaces11.
Casting nanocomposite membranes using controlled
temperature/humidity chamber. From left to right: Julian Taurozzi (now
at NIST), Volodymyr Tarabara, Alex Wang (now with Pentair, Inc.), Adam
Rogensues (now with Severn Trent)
Another example of how functional nanoparticle can be used to improve
membrane performance is the hybrid ozonation-ultrafiltration hybrid process.
This process is at the focus of the NSF-funded research project
at Michigan State University. The combination of nanoparticle-based
functionalities with membrane separation in one hybrid unit improves the overall
process efficiency and remove excessive redundancy25-31.
In the hybrid system, ozonation is effective in mitigating membrane fouling
due to the oxidation of foulants by ozone and/or hydroxyl radicals. By
introducing nanoparticles such as Fe2O3 and
MnO2 at the membrane surface, the efficiency of the hybrid process
can be significantly enhanced due to both the catalytic effect of the
nanoparticles and more targeted oxidation of the NOM portion that is
concentrated at or near the membrane surface contributing to membrane fouling.
A unique aspect of this hybrid process is that due to the effect of catalytic
ozonation at the membrane surface, the surface remains relatively foulant-free;
therefore, in the absence of the fouling layer, foulant-membrane interactions
remain important for extended periods of membrane operation. This, in turn,
increases the relevance of membrane surface engineering for longer term membrane
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H. G., Holt, J. K., Stademann, M., Grigoropoulos, C. P., Noy, A. and Bakajin, O.
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B., Grigoropoulos, C. P., Noy, A. and Bakajin, O. Fast mass transport through
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S., Arul, H., Bosak, V. Z., Burban, A. F., Voice, T. C., Bruening, M. L. and
Tarabara, V. V. Effect of filler incorporation route on the properties of
polysulfone-silver nanocomposite membranes of different porosities, J. Membr.
Sci. 325 (2008) 58-68.
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Velamakanni, B. V. Addition of alumina to cellulose acetate membranes, J. Membr.
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Vankelecom, I. F. J. and Jacobs, P. A. Polysulfone-aerosil composite membranes:
Part 1. The influence of the addition of Aerosil on the formation process and
membrane morphology, J. Membr. Sci. 176 (2000) 63-73.
16. Nunes, S. P., Peinemann, K. V., Ohlrogge, K.,
Alpers, A., Keller, M. and Pires, A. T. N. Membranes of poly(ether imide) and
nanodispersed silica, J. Membr. Sci. 157 (1999) 219-226.
Jeong, B.H., Hoek, E. M. V., Yan, Y., Huang, X., Subramani, A., Hurwitz, G.,
Ghosh, A. K. and Jawor, A. Interfacial polymerization of thin film
nanocomposites: A new concept for reverse osmosis membranes, J. Membr. Sci. 294
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K., Bachas, L. G. and Bhattacharyya, D. Degradation of chlorinated organics by
membrane-immobilized nanosized metals, Environ. Prog. 23 (2004) 232-242.
19. Wu, L. and Ritchie, S. M. C. Removal
of trichloroethylene from water by cellulose acetate supported bimetallic Ni/Fe
nanoparticles, Chemosphere 63 (2006) 285.
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nanoscale bimetallic particles in polyelectrolyte membrane matrix for reductive
transformation of halogenated organic compounds, J. Nanopart. Res. 7 (2005)
21. Xu, J. and Bhattacharyya, D. Fe/Pd nanoparticle
immobilization in microfiltration membrane pores: Synthesis, characterization,
and application in the dechlorination of polychlorinated biphenyls, Ind. Eng.
Chem. Res. 46 (2007) 2348-2359.
22. Dai, J. and Bruening, M.
L. Catalytic nanoparticles formed by reduction of metal Ions in multilayered
polyelectrolyte films, Nanoletters 2 (2002) 497 - 501.
Dotzauer, D. M., Dai, J., Sun, L. and Bruening, M. L. Catalytic membranes
prepared using layer-by-layer adsorption of polyelectrolyte/metal nanoparticle
films in porous supports, Nano Lett. (2006) 2268-2272.
L.F., Shamsuzzoha, M. and Ritchie, S.M.C. Preparation of cellulose acetate
supported zero-valent iron nanoparticles for the dechlorination of
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30. Kim, J., Davies, S. H. R., Baumann, M. J., Tarabara, V. V.
and Masten, S. J. Effect of ozone dosage and hydrodynamic conditions on the
permeate flux in a hybrid ozonation-ceramic ultrafiltration system treating
natural waters, J. Membr. Sci. 311 (2008) 165-172.
31. Kim, J., Shan, W. Q., Davies, S. H. R., Baumann, M. J.,
Masten, S. J. and Tarabara, V. V. Interactions of Aqueous NOM with Nanoscale
TiO2: Implications for Ceramic Membrane Filtration-Ozonation Hybrid Process,
Environ. Sci. Technol. 43 (2009) 5488-5494.
Copyright AZoNano.com, Professor Volodymyr Tarabara (Michigan