Transport and structural characteristics of heterogeneous ion-exchange membranes with varied dispersity of the ion exchanger

The structural and transport (conductivity and diffusion permeability) properties of cation- and anion-exchange membranes with different dispersity of ion-exchange resin particles have been studied. Experimental cation-exchange MK-40 and anion-exchange MA-41 membranes with varying particle sizes of ion exchange resin from <20 μm to <71 μm are manufactured at LLC IE Shchekinoazot (Russia). A comparative analysis of the structural characteristics of membranes using SEM reveals the anisotropy in the properties of the surface and section. The internal phase of the membrane is characterized by large values of the fraction and size of the ion exchanger and macroporosity. A comparison of the concentration dependences of the specific conductivity and diffusion permeability of experimental membranes is performed. Analysis of the values of model transport and structural parameters shows that with a decrease in the size of ion exchanger particles, an increase in the conductivity of the gel phase is observed from 0.39 to 0.47 S/m and from 0.15 to 0.26 S/m for cation- and anion-exchange membranes, as well as a redistribution of current transfer paths in the membrane. An increase in the contribution of transfer through the channel of the internal equilibrium solution is revealed, while the transfer numbers of counterions changes slightly. Information about changes in the structure of transport channels in membranes with different sizes of ion exchanger particles, obtained based on the analysis of model parameters, is consistent with the data of independent studies of the morphology of their surface and section using the SEM method.