Transport parameters of ion-exchange membranes in concentrated solutions

The state of water in an MK-40 ion-exchange membrane is studied by means of differential scanning calorimetry (DSC). The effect of saturated electrolyte solutions on the structure of membranes, including thermal treatment at 373 K, is considered. The endothermic peaks of solutions in a membrane can occupy various positions with respect to the equilibrium solution peak. The endotherm of ice melting in the membrane can coincide with the equilibrium solution endotherm or shift to higher or lower temperatures with respect to the peak corresponding to the equilibrium solution. This arrangement of endotherms can be accounted for by various degrees of electrolyte entering the pore space of a membrane. The DSC method enables one to make a conclusion on the variation of a membrane structure under thermal treatment, the state of solution in pores, and to qualitatively estimate the diffusion transport of electrolyte through a membrane.