Organic/inorganic Nanohybrid Membranes for Nanofiltration of Nonaqueous Solutions
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AA8.8.1
Organic/ inorganic Nanohybrid Membranes for Nanofiltration of Nonaqueous Solutions
Toshinori Tsuru, Hiroyasu Kondo, Tomohisa Yoshioka, and Masashi Asaeda Department of Chemical Engineering, Hiroshima University Higashi-Hiroshima 739-8527, JAPAN
ABSTRACT Silica/zirconia (SZ; Si/ Zr molar ratio = 9/1) membranes having pore sizes in the range of 1~ 3 nm were prepared by the sol-gel process. Organic/ inorganic hybrid membranes were developed by modifying the surface of the silica-zirconia porous membranes via a gas-phase reaction with trimethylchlorosilane (TMCS) to give a surface that was modified with a monolayer of TMCS. Using nanopermporometry, it was found that the inner surface of membrane pores with diameters larger than several nms were successfully modified with TMCS. TMCS-modified membranes showed approximately the same permeability, Lp, irrespective of water concentration (10 and 100 ppm) in hexane. In contrast, an unmodified membrane, showed a decrease in Lp with increasing water concentration, which was pronounced at low permeation temperatures. This suggests that small amounts of water adsorbed to the inner surface of unmodified silica-zirconia membranes and blocked the permeation of hexane.
INTRODUCTION Separation membranes have been developed for applications in aqueous systems such as desalination and drinking water treatment. It has recently been proposed that membrane separation could be expanded to a variety of applications such as the separation of non-aqueous solutions and the filtration of non-aqueous solutions. Several types of polymeric membranes have been investigated for possible use in the regeneration of a wide variety of solvents (Machodo et al. 2000; Bhanushali et al. 2001). However, such polymeric membranes do not cover all the potential applications. On the other hand, ceramic porous membranes, which have excellent resistance to most organic solvents and can be used over a wide temperature range, have the potential for use in the separation and filtration of nonaqueous solutions (Guizard et al 2002; Tsuru 2001a; Tsuru et al 2001b). From the viewpoint of surface chemistry, most ceramic membranes have hydrophilic properties because the surface of the metal oxide is hydrated, thus forming hydroxyl groups such as silanol (-SiOH) groups (Brinker and Scherer, 1990). On the other hand, organic materials have a wide variety of surface characteristics although their thermal resistance is low. Therefore, it would be expected that the use of organic/ inorganic hybrid materials could result in improved thermal and chemical resistance and that the surface chemistry could be well controlled. In this study, silica-zirconia porous membranes were fabricated by a sol-gel process, and modified with trimethylchlorosilane (TMCS) to produce organic-inorganic hybrid membranes in the nanometer scale. The permeation mechanism of pure non-aqueous solvents were then investigated using such membranes. EXPERIMENTAL
AA8.8.2
Silica-zirconia colloidal sol solutions having a Si/ Zr molar ratio of 9/ 1 wer
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