A Model Description of Diffusion Permeability of Bilayer Ion-Exchange Membranes

A model approach is developed, which enables one, using the concentration dependences of the diffusion permeability for individual layers, to estimate the density of a diffusion flux through a bilayer membrane, determine the concentration of a virtual solution at the interface between the membrane layers, and find the thickness of each layer that has constant diffusion characteristics. The approach is verified by the example of a perfluorinated MF-4SC membrane, with its surface being modified with polyaniline under different conditions. The adequacy of the approach is confirmed by a satisfactory coincidence of the modified layer thicknesses calculated in terms of the model and found by the optical examination of membrane sections.