State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, PR China.
Langmuir. 2011 Aug 16;27(16):10274-81. doi: 10.1021/la200219k. Epub 2011 Jul 19.
The free energies of ion equilibrium partition between an aqueous KCl solution and nanofiltration (NF) membranes were investigated on the basis of the relationship of the transmembrane electrical potential (TMEP) and rejection. The measurements of TMEP and rejection were performed for Filmtec NF membranes in KCl solutions over a wide range of salt concentrations (1-60 mol·m(-3)) and pH values (3-10) at the feed side, with pressure differences in the range 0.1-0.6 MPa. The reflection coefficient and transport number, which were used to obtain the distribution coefficients on basis of irreversible thermodynamics, were fitted by the two-layer model with consideration of the activity coefficient. Evidence for dielectric exclusion under the experimental conditions was obtained by analyzing the rejection of KCl at the isoelectric point. The free energies were calculated, and the contribution of the electrostatic effect, dielectric exclusion, steric hindrance, and activity coefficient on the ion partitioning is elucidated. It is clearly demonstrated that the dielectric exclusion plays a central role.
基于跨膜电动电势 (TMEP) 和截留率的关系，研究了 KCl 水溶液与纳滤 (NF) 膜之间离子平衡分配的自由能。在进料侧，在 0.1-0.6 MPa 的压力差范围内，对 Filmtec NF 膜在 KCl 溶液中的 TMEP 和截留率进行了广泛的盐浓度 (1-60 mol·m(-3)) 和 pH 值 (3-10) 范围内的测量。使用不可逆热力学获得分配系数的反射系数和迁移数，通过考虑活度系数的双层模型进行拟合。通过分析等电点时 KCl 的截留率，获得了实验条件下介电排斥的证据。计算了自由能，并阐明了静电效应、介电排斥、空间位阻和活度系数对离子分配的贡献。显然，介电排斥起着核心作用。
