PHYSICOCHEMICAL PRINCIPLES OF TESTING ION-EXCHANGE MEMBRANES

The results of investigations into concentration dependences of a wide number of transport characteristics pertinent to ion-exchange membran es of different production are generalized. A series of experimental p rocedures for measuring electrotransport characteristics of membrane m aterials under comparable experimental conditions is suggested. The na ture of concentration dependences of electroconductivity, diffusive an d electroosmotic permeability, and potentiometric transport numbers in a wide range of concentrations of equilibrium NaCl solutions is discu ssed. It is suggested that three concentration zones, which correspond to certain physicochemical conditions of the NaCl solution and membra ne, be singled out in order to characterize changes in the electrotran sport properties. All the membrane properties studied are found to be controlled by the content and state of water in swollen samples that r epresent phase-separated conducting systems. Parameters of the two-pha se model, which allow one to elucidate the reasons for distinctions in electrotransport of ions and water in ion-exchange membranes, are rep orted and compared. The research performed lays a physicochemical foun dation for testing membranes with the aid of the approaches that are d escribed in the paper.