DETERMINATION OF SURFACE DENSE LAYER STRUCTURE PARAMETERS OF THE ASYMMETRIC MEMBRANE BY GAS PERMEATION METHOD

Two kinds of pure non-sorbable gases (a and b) are used to determine the permeability and the separation factor of the asymmetric membrane of the type employed in Monsanto's Prism system. Mathematical models have been developed to relate the gas permeation characteristics to the dense skin structure parameters (the dense skin thickness, the surface porosity and the mean pore size) of the asymmetric membrane. These models were applied to determine the dense skin thickness, the surface porosity and the mean pore size of the asymmetric polysulfone fiat and hollow fiber membranes prepared in our laboratory. H2 and N2 were used as test gases. The validity of the dense skin structure parameters obtained by the gas permeation method was examined by the resistance permeation model given by Henis and Tripod. The results show that the dense skin structure parameters determined by this method substantially reflect the real structure characteristics of the dense skin of the asymmetric membrane. © 1990.