Active Transport of Heavy Metal Ions through Polymeric Blended Membranes

[1]将聚异丁烯-马来酸酐共聚物（ISBN）和聚苯乙烯磺酸（PSA）与聚乙烯醇（PVA）共混制备了两种聚合物膜。本文研究了钠、镁、镍离子的交换平衡、渗透和富集分离。ISBN/PVA膜在弱酸性溶液和水中均有溶胀趋势，可发生缩醛化，但离子交换容量降低，渗透通量显著下降。通量数据与膜厚度成反比;然后，从渗透速率和离子交换平衡评价膜中金属离子的有效扩散系数。对于二元离子溶液，重金属与钠离子的分离因子也由上坡迁移条件下的最大浓度确定。发现分离因子对应于每个初始通量的比率。[2]渗透速率 ...更多信息 本文用两个模型解释了金属离子在阳离子交换膜NeoseptaCM-1上的迁移。模型1包括平衡常数Kex、金属离子和质子的自扩散系数三个参数，而模型2包括膜表面的反应速率常数和膜内的修正速率常数以及Kex。前者仅适用于一价离子的渗透。因此，在离子渗透过程中，水相和膜相之间的界面似乎不是平衡的：非平衡过程。[3]为了开发优先于乙醇渗透的膜，在反应器中的多孔聚丙烯基底膜（Duragard 2500）上发生硅氧烷的等离子体聚合以及硅氧烷浇铸膜的等离子体表面处理。在减压渗透蒸发实验中，通过乙醇对水的分离因子和渗透通量考察了膜的选择渗透性。发现对于类似于硅橡胶的铸膜，最大分离因子约为10;然而，六甲基二硅氧烷的等离子体聚合带来了较低的选择性，但较高的乙醇通量。目前正在开发更优选的膜以应用于渗透蒸发过程。少

[1] Two kinds of polymeric membranes were prepared by blending poly(isobutylene-alt.comaleic anhydride)(ISBN) and polystylene sulfonic acid(PSA) with polyvinylalchol(PVA). Studies were made on the ion-exchange equilibria, permeation and enrichiment separation of sodium, magnesium and nickel ions. Having a trend to swelling in weak acid solution as well as in water, the ISBN/PVA membranes allowed to acetallize; however, the permeation fluxes decreased remarkably as a result of lowering of the ion-exchange capacity. The flux data are inversely proportional to the membrane thickness; then, effective diffusivities of the metal ions in the membrane were evaluated from the permeation rate and ion exchange equilibrium. For the binary ionic solutions, separation factor of heavier metal to sodium ion was also determined from the maximum concentrations under conditions of uphill transport. It was found that the separation factor corresponds to the ratio of each initial flux.[2] Permeation rates … More of metal ions across a cation-exchange membrane, Neosepta CM-1, have been explained from two Models. model-1 includes the three parameters of the equilibrium constant,Kex, self-diffusion coefficients of metal ion and proton, while model-2 does the reaction rate constant at the membrane surface and a modified rate constant within the membrane as well as Kex. The former could be applied only for the permeation of monovalent ions. Thus, it appears that during the ion permeation the interface between the aqueous and membrane phases is not in equilibrium: non-equilibrium process.[3] To develop the membrane preferential to ethanol permeation, plasma polymerization of siloxanes was taken place on a porous polypropylene substrate membrane (Duragard 2500)in a reactor as well as the plasma surface-treatment of silicone casting membranes. The membrane perm-selectivity was examined in terms of the separation factor of ethanol to water and the permeation flux in pervaporation experiments under reduced pressure. The maximum separation factor is found to be about 10 for a casting membrane similar to silicone rubbers; however, the plasma polymerization of hexamethyldisiloxane brought about lower selectivity but higher flux of ethanol. Presently more preferential membranes are being developed to apply for pervaporation processes. Less