Dielectric properties of cellulose acetate membranes in aqueous salt solution.

Abstract

Dielectric measurements were carried out for cellulose acetate (CA) membranes in different degrees of acetyl substitution (DS) in aqueous salt solution. Relative permittivities and conductivities of the membranes immersed in NaCl aqueous solutions were determined by use of a theory on the dielectric relaxation of the interfacial polarization.The relative permittivities of the CA membranes were directly proportional to the water contents of the membranes.The salt permeabilities of the membranes estimated from the conductivities were in agreement with the results of the measurements of the salt permeabilities presented by other authors.The relation between the conductivity and the NaCl concentration of the external aqueous solution showed that the CA membranes were weakly charged. The value of the effective fixed charge density estimated from the dielectric data was 15 m equiv./1, which was in conformity with the results of the membrane potential measurements by other authors.