科研之友
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摘要
The recent development of solvent and temperature-resistant. hydrophilic zeolite NaA membranes has made it possible to overcome the limitations of hydrophilic polymeric membranes. Zeolite membranes have uniform and molecular-sized pores, and they separate molecules based on differences in the molecules' adsorption and diffusion properties. Strong electrostatic interaction between ionic sites and water molecules makes the zeolite NaA membrane very hydrophilic. Zeolite NaA membranes are thus well suited for separating liquid-phase mixtures by pervaporation. Total flux for unsymmetrical dimethylhydrazine (UDMH)-water mixtures was found to vary from 0.329 to 0.215 kg/m(2).h with increasing UDMH concentration from 1 to 20 wt.%. Ionic sites of the NaA zeolite matrix play a very important role in water transport through the membrane. These sites act both as water sorption and transport sites. Surface diffusion of water occurs in an activated fashion through these sites. The precise nanoporous structure of the zeolite cage helps in a partial molecular sieving of the large solvent molecules leading to high separation factors. A comparison between experimental flux and calculated flux using Stephan Maxwell (S.M.) correlation was made and a linear trend was found to exist for water flux through the membrane with UDMH concentration.
- 出版日期2011-10-17
