Mathematical Simulation of Gas Transfer through a Bilayer Membrane with Account for Adsorption Kinetics

Abstract

Mathematical simulation has been employed to study the permeability of a bilayer membrane taking into account finite rates of adsorption on the external surfaces of the membrane and internal diffusion in it. Analytical expressions are derived for transmembrane gas flux and permeability of the membrane. It has been revealed that the permeability may depend on the direction of gas flux (asymmetry effect). It has been shown that the asymmetry effect arises at different values of the parameters of the isotherms of gas sorption in membrane layers at a finite gas pressure. The main characteristics that govern the degree of asymmetry have been determined and analyzed. The rate of adsorption has been found to substantially influence the magnitude of the asymmetry effect in the bilayer membrane. It has been found that a two-layer membrane can function as a diffusion "diode", if adsorption is the limiting stage of gas transfer.