Effect of modification of ion-exchange membrane MF-4SK on its polarization characteristics

Modifications of perfluorinated membrane MF-4SK are studied by a membrane voltammetry method. Various techniques used for physicochemical modification of the membrane (variation of conditions of its chemical conditioning, insertion of tetrabutylammonium cations) exert predicted action on its structural and electrotransport properties. Correlation is established between variations in the slope of the ohmic segment of a voltammetric curve, the magnitude of the limiting electrodiffusion current, and the potential of the system’s conversion into an overlimiting state and the electrotransport properties of membranes and their structural characteristics that are obtained by independent methods of impedance conductimetry and standard porosimetry. The increase in the limiting current for membranes subjected to a thermal oxidizing treatment is explained by a change in the content and state of water in the membrane bulk. Effects of acceleration of the occurrence of an overlimiting state of the membrane saturated with tetrabutylammonium cations is discovered and possible reasons for this phenomenon are discussed. For membranes saturated with tetrabutylammonium cations, a correlation is established between the limiting current and electroosmotic phenomena.