Permeation characteristics of electrolytes and neutral solutes through titania nanofiltration membranes at high temperatures.
Permeation characteristics of electrolytes and neutral solutes through titania nanofiltration membranes at high temperatures.
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DOI：
10.1021/la100791j
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发表时间：
2010-04
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影响因子：
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通讯作者：
T. Tsuru;Kazuhisa Ogawa;M. Kanezashi;Tomohisa Yoshioka
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作者：
T. Tsuru;Kazuhisa Ogawa;M. Kanezashi;Tomohisa Yoshioka
采用溶胶-凝胶法成功制备了孔径控制在0.7 ~ 2.5 nm、截留分子量（MWCO）在500 ~ 2000范围内的纳米多孔二氧化钛膜，并在30-80 ℃温度范围内对膜的传输特性进行了评价。随着温度的升高，渗透通量增加2至3倍，这取决于孔径。水的渗透机制被认为是不同的粘性流，并解释了封闭孔隙内的水（自由水/结合水/不冻水）的状态。中性溶质的截留率，如棉子糖，其分离机制是分子筛（空间位阻），随着温度的下降，而电解质（MgCl（2）和NaCl），其分离机制是电荷效应（唐南排斥），是近似恒定的。中性和电解质溶质的温度依赖性分析使用Spiegler-Kedem方程，通过结合用于扩散率和粘度的Arkenius方程，我们得到DeltaE（m），扩散活化能，在消除粘度的影响后。对于大的Δ E（m）（其对应于基于分子筛的中性溶质的截留率），截留率随温度降低，但对于小的Δ E（m）（其对应于基于电荷效应的电解质的截留率）保持不变。
Nanoporous titania membranes with controlled pore sizes ranging from 0.7 to 2.5 nm, which had molecular weight cutoffs (MWCO) ranging from 500 to 2000, were successfully prepared by sol-gel processing, and the transport characteristics were evaluated across a temperature range of 30-80 degrees C. With increasing temperature, the permeate flux increased 2- to 3-fold, depending on the pore size. The water permeation mechanism was found to be different from viscous flow and was explained by the state of the water (free water/bound water/nonfreezing water) inside confined pores. The rejection of neutral solutes such as raffinose, the separation mechanism of which is molecular sieving (steric hindrance), decreased with temperature whereas that of electrolytes (MgCl(2) and NaCl), the separation mechanism of which is the charge effect (Donnan exclusion), was approximately constant. The temperature dependence of neutral and electrolyte solutes was analyzed using the Spiegler-Kedem equation by combining the Arrhenius equations for diffusivity and viscosity, which we obtained DeltaE(m), the activation energy of diffusion, after eliminating the effect of viscosity. For large DeltaE(m), which corresponds to the rejection of neutral solutes on the basis of molecular sieving, rejection decreased with temperature but remained unchanged for small DeltaE(m), which corresponds to the rejection of electrolytes based on the charge effect.