Preferential Permeability of Benzenesulfonate Ions in Electrodialysis

Abstract

Transport properties of benzenesulfonate and methyl-substituted benzenesulfonate ions in electrodialysis were studied.
The preferential p ermeability of benzenesulfonateions decreased with the increasing of applied current density, the concentration decreaseing of dialysing solution and the increasing in the number of methyl group contained. The permeability was related to the Stanton number (Se), a dimensionless operating parameter, defined as the ratio of ionic flux in the direct ion to an electrodialysis membrane to ionic flux in the direction of the bulk flow of electrolyte. As the Stanton number increased, the permeability decreased and showed definite values for St>10^-3. The permeability coefficient calculated from the mobility ratio of the ions in ionexchange membrane in a single-solute-solution and the composition of ions in membrane in a binary-solute-solution was far less than that obtained for desalting experiments. It is suggested that chloride ion, which is more mobile and present much more in the membrane than benzenesulf onate ions, causes an acceleration of the migrating velocity of each less mobile benzenesulfonate ion.