Permselectivity of Chloride and Sulfate Ions through Vinylon Membranes

Studies on Ion Exchange Membranes (11)

Abstract

The permeability of sulfate ions through an anionselective membrane is lower than that of chloride ions. This is, in general, considered chiefly due to their strong interaction with exchange groups in the resin phase.
In order to know how this interaction contributes to the permselectivity of sulfate ions, the authors prepared the Vinylon membrane possessing no exchange groups and measured the permse-lectivity of sulfate ions against chloride ions by electrodialysis experiments by using a seven-comp-artment apparatus equipped with the Vinylon membranes and cation-selective membranes. The results were compared with the data obtained from the use of an ordinary anion-selective membrane.
As the result, it was found that the values of the permselectivity coefficient of sulfate ions were 0.015-0.03 for the Vinylon membrane and much lower than the values for the anion-selective membrane. This indicated that the Vinylon membrane made it more difficult to permeate sulfate ions than the anion-selective membrane.
From the above results, it was concluded that the preferential impermeability of sulfate ions through membranes was influenced by not only by the extent of the interaction with the exchange groups, but largely influenced by the compactness of the pore structure of the membranes.