Studies on the electrical diffusivities of mono-carboxylates through heterogeneous anion exchange membranes

Heterogeneous anion exchange membranes have been prepared by solution casting technique with poly (vinyl chloride) (PVC) as inert binder and anion exchange resin (-300 + 400 mesh) by varying their blend ratio from 60 : 40 to 30 : 70. The membranes were characterized with respect to their physical, mechanical, and electrochemical behavior. The transport behavior of such membranes was studied in the solutions of different homologous monocarboxylate salts starting from formate to butyrate. Membrane conductance values, in conjunction with the solution conductance, were used to determine the isoconductance points following the microheterogeneous model developed by Zabolotsky and Nikonenko, J Membr Sci 1993, 79, 181. Frorn the electro conductivity ((kappa) over bar) and exchange capacity ((Q) over bar) of the joint gel phase, the diffusion coefficients of different carboxylate anions have been determined. The specific conductivities of the joint gel phase decreases in the order (kappa) over bar formate > (kappa) over bar acetate > (kappa) over bar propionate > (kappa) over bar > butyrate. For any specific carboxylate counter ion, the (kappa) over bar (70) > (kappa) over bar (60) > (kappa) over bar (50) > (kappa) over bar (40) .For any particular resin loading the diffusion coefficient in membrane for formate > acetate > propionate > butyrate. The membranes Studied here (varying in their blend ratios) may be synchronized by nearly same heterogeneity factor P of value 0.38 +/- 0.04. (c) 2007 Wiley Periodicals, Iiic.