Transport properties of bilayer and multilayer surface-modified ion-exchange membranes

This work aims to study changes in the electrochemical and transport properties of bilayered and multilayered ion-exchange membranes based on a Ralex AMH heterogeneous ion-exchange membrane. The composites studied are: a bilayer membrane consisting of a thin layer of perfluorocarbon cation-exchanger deposited on the surface of the Ralex membrane (Ralex/MF 4SK) as well as a composite with polyaniline based on it (Ralex/MF 4SK/PANi), and a composite with a polyaniline and Ralex membrane (Ralex/PANi). The transport properties of the composite membranes are studied in electrolyte solutions of different natures by different methods. The concentration dependences of the diffusion permeability and specific conductivity of the initial and composite membranes in NaCl and HCl solutions were investigated, and the water transport numbers in NaCl solutions were measured. Electrodiffusion coefficients were calculated and the concentration dependences of electro-migration numbers of counterion transport were obtained. The effect of asymmetry of diffusion permeability when the orientation of the composite membranes with respect to the flux of electrolyte is changed was studied. A study of the current-voltage characteristics of the original membrane and composites based on it shows that the application of the MF-4SK film leads to an increase in the reaction rate of water-splitting reaction at the emerging cation/anion-exchanger interface. In the case of composites with polyaniline, there is an increase in the limiting current density in comparison with the initial sample and a significant potential oscillation in the overlimiting mode, which indicates a significant contribution of electroconvection in the overlimiting mass-transfer.