The interplay between the ion exchange capacity, water content and concentration dependences of conductivity, diffusion permeability, and counterion transport numbers (counterion permselectivity) of CJMA-3, CJMA-6 and CJMA-7 (Hefei Chemjoy Polymer Materials Co. Ltd., China) anion-exchange membranes (AEMs) is analyzed using the application of the microheterogeneous model to experimental data. The structure–properties relationship for these membranes is examined when they are bathed by NaCl and Na2SO4 solutions. These results are compared with the characteristics of the well-studied homogenous Neosepta AMX (ASTOM Corporation, Japan) and heterogeneous AMH-PES (Mega a.s., Czech Republic) anion-exchange membranes. It is found that the CJMA-6 membrane has the highest counterion permselectivity (chlorides, sulfates) among the CJMAED series membranes, very close to that of the AMX membrane. The CJMA-3 membrane has the transport characteristics close to the AMH-PES membrane. The CJMA-7 membrane has the lowest exchange capacity and the highest volume fraction of the intergel spaces filled with an equilibrium electroneutral solution. These properties predetermine the lowest counterion transport number in CJMA-7 among other investigated AEMs, which nevertheless does not fall below 0.87 even in 1.0 eq L−1 solutions of NaCl or Na2SO4. One of the reasons for the decrease in the permselectivity of CJMAED membranes is the extended macropores, which are localized at the ion-exchange material/reinforcing cloth boundaries. In relatively concentrated solutions, the electric current prefers to pass through these well-conductive but nonselective macropores rather than the highly selective but low-conductive elements of the gel phase. It is shown that the counterion permselectivity of the CJMA-7 membrane can be significantly improved by coating its surface with a dense homogeneous ion-exchange film.

Optimum values of parameters of hot pressing of heterogeneous ion-exchange membranes pressure, exposure duration) with the aim of creating geometrical profiles on their surfaces are determined. A method of optical visualization of membrane profiles and a diffusion technique of diagnostics of through pores in the membranes are developed and substantiated. Most important physicochemical and physicomechanical characteristics of profiled membranes are investigated. It is shown that the major obstacle in the production of profiled cation-exchange heterogeneous membranes is encapsulation of grains of the ion-exchange resin by an inert polyethylene film, which leads to an increase in the surface resistance of the membranes and to a decrease in the fraction of their active surface areas. The profiling of heterogeneous anionexchange membranes is accompanied by an increase in their microscopic porosity and diffusion penetrability.

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Polarization characteristics of electromembrane systems (EMS) based on the Russian commer cial heterogeneous membranes MA 40 and MA 41, the anion exchange heterogeneous membrane AMH (Mega, Czech Republic), and the modified membrane MA 40M are studied by the method of rotating mem brane disk in dilute sodium chloride solutions. The effective transport numbers of ions are found; the partial voltammetric characteristics (VAC) with respect to chloride and hydroxyl ions are measured; the limiting cur rent densities are calculated as a function of the membrane disk rotation rate. In terms of the theory of the overlimiting state of EMS, based on experimental VAC and the dependences of the effective transport num bers on the current density, the following internal parameters of systems under study are calculated: the space charge and electric field strength distribution over the diffusion layer and the membrane. It is shown that water dissociation can be virtually completely eliminated by substituting chemically stable quaternary ammo nium groups inert with respect to water dissociation in the surface layer of a heterogeneous anion exchange membrane MA 40 for the active ternary and secondary functional amino groups. The maximum electric field strength values at the membrane/solution interface, which were found in the framework of the theory of over limiting state, turned out to be close for all anion exchange membranes studied, namely, (7-9) × 10 6 V/cm. This suggests that it is the nature of ionogenic groups in the surface layer rather than the field effect that plays the decisive role in the membrane ability to accelerate the water dissociation reaction. It is proved experimen tally that in highly intense current modes of the electrodialysis process, the thermal hydrolysis of quaternary ammonium bases occurs in strongly basic MA 41 and AMH membranes by the Hofmann reaction to form ternary amino groups catalytically active in water dissociation reaction. Based on the concept on the catalytic mechanism of water dissociation, the fraction of ternary amino groups formed by thermal hydrolysis in the surface layer (the space charge region) of monopolar anion exchange membranes MA 41 and AMH is assessed quantitatively as 0.7 and 6.5%, respectively.