Theoretical and experimental investigation of diffusion permeability of hybrid MF-4SC membranes with silica nanoparticles

The diffusion permeability through hybrid materials based on a Nafion-type membrane and hydrated silica is investigated using the Nernst–Planck approach. A method of quantitative evaluation of physicochemical parameters (averaged and individual diffusion coefficients and averaged distribution coefficients of ion pairs in the membrane) of system “electrolyte solution–ion-exchange membrane–water” is developed. The parameters of hybrid membranes on the base of MF-4SC and hydrated silica are obtained from experimental data on diffusion permeability of HCl and NaCl solutions using theoretical calculations. It is shown that the dependence of computed diffusivities of sodium cation and proton upon SiO2 content has a minimum at 5% and 7%, respectively. At the same time experimental values of distribution coefficients of HCl and NaCl molecules reach the maximum at 1.5–3% of SiO2 content. The results obtained are in a good correlation with the physicochemical model of the limited elasticity of the membrane pore walls.