Electrodialytic transport properties of anion-exchange membranes in the presence of alpha-cyclodextrin

Electrodialysis of mixed salt solutions, sodium chloride and sodium sulfate , and sodium chloride and sodium nitrate, was carried out in the presence o f alpha -cyclodextrin using commercial anion-exchange membranes. It was con firmed by several methods that the compound existed in the membrane matrix when the membrane had been immersed in its aqueous solution, though the mol ecular weight of alpha -cyclodextrin is relatively high. In electrodialysis , sulfate ions, large and strongly hydrated anions, easily permeated throug h the membranes and nitrate ions, less hydrated anions, permeated with diff iculty through the membranes in the presence of alpha -cyclodextrin. Becaus e alpha -cyclodextrin is a hydrophilic compound, which has many ether and a lcoholic groups, the hydrophilicity of the anion-exchange membranes is thou ght to increase. Thus, sulfate ions easily permeate and nitrate ions permea te with difficulty. This proves that the hydrophilicity of the anion-exchan ge membranes controls permselectivity between anions through the membranes.