ELECTROCHEMICAL PROPERTIES OF ASYMMETRIC CELLULOSE-ACETATE MEMBRANES

Dielectric measurements and membrane potential measurements were carried out for asymmetric cellulose acetate (CA) membranes in aqueous solution. In view of the results of the measurements, it was concluded that the membrane potential properties of asymmetric CA membranes capable of rejecting solutes severely could be attributed to the dense layer in the membrane. This conclusion was supported by the membrane potential theory on the basis of the two-layer model. It was found that the membrane potentials of the membranes capable of rejecting solutes severely showed a minimum. This was explained by the theory including the concentration polarization caused by osmotic flow. The effective fixed charge density of the asymmetric CA membranes increases with the increase in the salt rejection of the membranes. The mobility ratio of a cation to an anion decreases with the increase in the stokes radius of the cation in aqueous solution and the effective fixed charge density of the membranes. From these results, it may be concluded that the ions in the membranes are hydrated and interact with the fixed charge of the membrane. © 1990.