Experimental and Theoretical Studies of Asymmetry of Transport Properties of Modified Ultrafiltration Membranes

Ultrafiltration membranes based on polyamide and polysulfone modified by polyelectrolytes are produced. The effect of the nature of a polymer matrix and modifier on the rejection ability and diffusion permeability of membranes is studied. The effect of the asymmetry of transport properties, which is manifested at different orientations of membrane with respect to the flow of electrolyte, is quantitatively evaluated. It was demonstrated that the asymmetry of substance transport is more pronounced in the ultrafiltration regime than in the diffusion of sodium chloride solutions. A mathematical model that describes the filtration of binary electrolyte solutions on partially charged two-layer membranes is proposed and the corresponding boundary-value problem is solved analytically. The qualitative correspondence between theoretical calculations and experimental data on the asymmetry effect of the rejection ability of two-layer system is revealed.