| Abstract: | Since the development of a stable ion-exchange membrane with low electric resistance in 1950, ion-exchange membranes have advanced from laboratory scale operations to industrial productions with extensive applications. Although ion separation is the most common function of ion-exchange membranes, most membranes exhibit non-selective removal of specific ions. In membrane technologies, permselectivity is defined as the preferential transport of specific ionic species through membranes that bear fixed charges in the polymer matrix based on Donnan effect and Donnan exclusion. Permselectivity of membranes can be discussed in two categories: the selectivity between co-ions and counterions and that between different counterions. An ideal permselectivity membrane should exhibit a high retention capacity for co-ions, a high transport number and selectivity for counterions, and in some cases, selectivity between monovalent and divalent counterions or among ions with same charge, e.g., NO3− and Cl−. In general, the ion separation ability depends on the ionic size, affinity of the counterions toward the membrane, and the difference in ion mobility within the membrane. Therefore, significant research has focused on the modification of pore size, surface functional groups, and microstructures of the membrane via various synthesis procedures in order to precisely tune membrane permselectivity. Previous efforts on selective membranes for anion and cation removal from wastewater, respectively, were reviewed. System integration involving permselective membranes and electrochemical processes for wastewater treatment is presented. Finally, examples of industrial applications of permselective membranes for the treatment of wastewaters were discussed. Overall, this chapter provides comprehensive information on the advances and applications of permselective membranes for the remediation of specific impaired waters. |
