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Abstract: A series of composite ion-exchange membranes based on an heterogeneous cation-exchange MK‑40 membrane and polyaniline is obtained under the conditions of electrodiffusion of a monomer and an oxidizing agent. The process of polyaniline synthesis on the membrane surface is accompanied by recording of chronopotentiograms and pH of the solution leaving the desalination compartment. The initial cation-exchange MK-40 membrane and obtained composites based on it are studied by voltammetry and chronopotentiometry in solutions of NaCl, CaCl2, and MgCl2in the same flow-type electrodialysis cell, in which the composites are obtained. To calculate the transport numbers of counterions in the membranes in solutions of CaCl2and MgCl2by chronopotentiometry, the apparent fraction of the conductive membrane surface in a solution of NaCl is calculated based on the experimental data on the potentiometric transport numbers of counterions in the membrane. The conditions for the synthesis of polyaniline on the surface of an heterogeneous MK-40 membrane which result in the preparation of samples with selectivity to singly charged ions are found out.

Abstract: Comprehensive characterization of basic MK-40 and Ralex CMH heterogeneous cation-exchange membranes and composite membranes with polyaniline based on them is performed including the determination of specific electrical conductivity and diffusion permeability; measurement of current–voltage curves in solutions of sodium, calcium, and magnesium chlorides and hydrochloric acid and curves of distribution of water with respect to the bond energies and effective pore radii as well as assessment of the transport structural parameters of a microheterogeneous model. The time of synthesis of polyaniline on the surface of cation-exchange membranes for obtaining samples with an anisotropic structure and asymmetric electric transport properties is determined by successive diffusion of a solution of an oxidizing agent and a monomer through the membrane into water. It is shown based on the analysis of the electric transport properties, structural characteristics, and model transport structural parameters of the membranes in solutions of singly and doubly charged ions that the obtained materials are promising for use in the processes of electrodialysis desalination of multicomponent solutions.