Relating performance of thin-film composite forward osmosis membranes to support layer formation and structure

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Osmotically driven membrane processes have the potential to treat impaired water sources, desalinate sea/brackish waters, and sustainably produce energy. The development of a membrane tailored for these processes is essential to advance the technology to the point that it is commercially viable. Here, a systematic investigation of the influence of thin-film composite membrane support layer structure on forward osmosis performance is conducted. The membranes consist of a selective polyamide active layer formed by interfacial polymerization on top of a polysulfone support layer fabricated by phase separation. By systematically varying the conditions used during the casting of the polysulfone layer, an array of support layers with differing structures was produced. The role that solvent quality, dope polymer concentration, fabric layer wetting, and casting blade gate height play in the support layer structure formation was investigated. Using a 1 M NaCl draw solution and a deionized water feed, water fluxes ranging from 4 to 25 L m(-2) h(-1) with consistently high salt rejection (>95.5%) were produced. The relationship between membrane structure and performance was analyzed. This study confirms the hypothesis that the optimal forward osmosis membrane consists of a mixed-structure support layer, where a thin sponge-like layer sits on top of highly porous macrovoids. Both the active layer transport properties and the support layer structural characteristics need to be optimized in order to fabricate a high performance forward osmosis membrane. (C) 2010 Elsevier B.V. All rights reserved
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This publication is based on work supported in part by Award No. KUS-C1-018-02, made by King Abdullah University of Science and Technology (KAUST); the WaterCAMPWS, a Science and Technology Center of Advanced Materials for the Purification of Water with Systems under the National Science Foundation Grant CTS-0120978; and Oasys Water Inc. We also acknowledge the NWRI-AMTA Fellowship for membrane technology (to Alberto Tiraferri) and a Graduate Fellowship (to Ngai Yin Yip) made by the Environment and Water Industrial Development Council of Singapore.
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Forward osmosis; Thin-film composite; Porous support; Polysulfone support layer; Support structure; Support formation; Membrane structure; Internal concentration polarization; CELLULOSE-ACETATE MEMBRANES; PHASE-SEPARATION PHENOMENA; WASTE-WATER RECLAMATION; HOLLOW-FIBER MEMBRANES; REVERSE-OSMOSIS; CONTACTOR PROCESSES; IMMERSION PRECIPITATION; ASYMMETRIC MEMBRANES; INVERSION MEMBRANES
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Journal of Membrane Science 367 (2011) 340–352
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