Influence of Titanium Dioxide Particles Percentage in Modifying Layer on Surface Properties and Current-Voltage Characteristics of Composite Cation-Exchange Membranes

Ion-exchange membranes are widely used as a key element in electromembrane processes, in particular, in the electrodialysis processing of solutions for wastewater treatment, the production of valuable medicinal and nutritional products, and many other applications. One of the main limiting factors in the development of electromembrane technologies is a low rate of mass transfer. A solution to this problem can be intensification of electroconvective mixing of the solution at the membrane surface by surface modification. Samples of composite membranes were prepared by forming a modifying film of perfloursolfonic acid polymer with the embedded TiO2 particles of the various percentage on the surface of a heterogeneous cation-exchange membrane MK-40. It has been shown that this modification leads to a multiple increase in the electric charge and a change in the parameters of geometric inhomogeneity of the membrane surface. It has been found that the optimal combination of these characteristics is achieved in the case of a sample containing 3 wt % TiO2, which provides a maximum increase (by a factor of 1.5) in the limiting current density due to electroconvection, which occurs according to the mechanism of electroosmosis of the first kind. The same sample demonstrates the minimum threshold values of the potential drop required for the transition from equilibrium electroconvection to the non-equilibrium one.