PORE-SIZE EVALUATION FOR FINE POROUS FREEZE-DRIED CELLULOSE-ACETATE MEMBRANE BY GAS SEPARATION

The pore size for a fine porous freeze-dried cellulose acetate membrane was evaluated by gas separation methods, where the Present-deBethune equation was applied. Separation coefficients were referred to the calculated value for each pore size from this equation. Nuclepore, Millipore VS, and Millipore VC, whose pore sizes were already known by bubble point method, were tested for this method. Pore diameters for this cellulose acetate membrane, thus determined, were about 25 and 40 A from Ar-Kr and N//2-Kr separation systems, respectively, which agreed well with the results from electron microscope (50 A) and N//2 gas permeability (50 A).