Studies of the effect of variation of blend ratio on permselectivity and heterogeneity of ion-exchange membranes

Heterogeneous ion-exchange membranes (both cationic and anionic types) have been synthesized by solution casting techniques using polyvinyl chloride (PVC) as binder and ion-exchange resin (−300+400 mesh). The binder:resin ratio varied from 60:40 to 30:70. The transport behavior of the membranes has been evaluated chronopotentiometrically in sodium chloride (NaCl) solutions of different concentrations. The different parameters E 0 (potential drop across the membrane at the instant of application of current I), E max (maximum potential drop across the membrane after the application of current I), Δ E (magnitude of the potential jump across the membrane at transition time τ), Iτ 1/2, τ, etc., have been evaluated. The isoconductance points were determined and based on the microheterogeneous model proposed by Zabolotsky and Nikonenko (J. Membrane Sci. 79 (1993) 181) the distribution factors β has been evaluated for both types of ion exchange membranes. The electroconductivity of the joint gel ( κ ̄ ) and pure gel phases ( κ ̄ ′ ) has been determined. At any particular solution concentration the transport number as well as the permselectivity of membranes increases with increased resin content of the membrane. The microheterogeneity factor β exhibits synchronization among the each set of four different membranes for both the cationic and anionic type.