Effect of mobile cation on zeolite-polyamide thin film nanocomposite membranes
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Effect of mobile cation on zeolite-polyamide thin film nanocomposite membranes Mary Laura Lind, Byeong-Heon Jeong,a) Arun Subramani,b) Xiaofei Huang, and Eric M.V. Hoekc) UCLA Civil & Environmental Engineering Department, and California NanoSystems Institute, University of California—Los Angeles, Los Angeles, California 90095 (Received 20 August 2008; accepted 2 December 2008)
Hybrid zeolite-polyamide thin film nanocomposite (TFN) reverse osmosis membranes were synthesized by incorporating Linde type A (LTA)-type zeolite molecular sieve nanocrystals in the interfacial polymerization reaction used to form polyamide thin films. Nanocrystals were prepared with two different mobile cations (Na+ and Ag+) exchanged within the LTA crystal matrix. Incorporation of molecular sieve nanocrystals into polyamide thin films during interfacial polymerization was verified by infrared spectroscopy. Both TFN membranes exhibited higher water permeability, while maintaining similar salt rejection to pure polyamide thin film composite membranes. Nanocomposite thin films containing LTA nanocrystals in the silver form (AgA) produced a greater increase in water permeability than those in the sodium form (NaA). Furthermore, AgA-TFN membranes exhibited more hydrophilic and smooth interfaces, which appeared to inhibit adhesion of bacteria cells onto the membranes. The AgA nanocrystals exhibited significant bactericidal activity; however, when encapsulated within polyamide thin films the antimicrobial activity was significantly reduced. I. INTRODUCTION
Water is fundamental for human survival and is a critical limiting resource powering the global economy through its use in agricultural irrigation, electricity production, and industrial processes. As demand approaches the amount of fresh water available, purification of nontraditional water from sources will be critical.1 Reverse osmosis (RO) membranes are now among the most popular technologies for producing fresh water from alternative waters—such as seawater, brackish groundwater, and wastewater—because commercially available RO membranes can produce high-quality water from virtually any source. However, RO membranes with higher water permeability, improved contaminant selectivity, and better fouling resistance are needed to reduce the operating costs, chemical consumption, and energy demand of producing high-quality water from alternative sources. a)
Present address: Hyundai & Kia Motors, 104 Mabuk-Dong, Giheung-Gu, Yongin-Si, Gyeonggi-Do 446-912, Korea. b) Present address: MWH, 618 Michillinda Avenue, Suite 200, Arcadia, CA 91007. c) Address all correspondence to this author. e-mail: [email protected] This paper was selected as an Outstanding Symposium Paper for the 2007 MRS Fall Meeting, Symposium V. DOI: 10.1557/JMR.2009.0189 1624
J. Mater. Res., Vol. 24, No. 5, May 2009
Nanotechnology promises to provide entirely new classes of functional materials for application to water purification—including better filter media, sorbents, catalysts, and membranes.2 Promising examples of advan
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