Abstract
The characteristic coefficients of ions in the ion-exchange membranes were investigated experimentally and the exchange affinities between ions and the ion-exchange membranes were obtained experimentally. The ratio of [KBA⋅ (KCA) -1] Other⋅ [KBA⋅ (KCA) -1] -1Neosepta where K is a selectivity coefficient remained constant at ca.1, on the condition that A, B, and C ions were of equal valence. Further, the ratio of (αBA⋅Q-1) Other⋅ (αBA⋅Q-1) -1Neosepta where α is a separation factor and Q is an exchange capacity was constant, giving the average value of 0.34 when A and B ions were monovalent and bivalent ions, respectively.
By applying the Fick's equation and no electric current to the flux through the ion-exchange membrane on Donnan dialysis, an equation was derived for Donnan dialysis in which feed ions and driving ions were of equal valence. The theoretically derived equation was fitted to the experimental values by adjusting diffusion coefficients. Thus, the diffusion coefficients of ions in the ion-exchange membrane which satisfied all the experimental data were determined. It was clearly shown that the ratio of the diffusion coefficient in the membrane to that in solution remained constant at 200 for H+ ions and at 70 for both K+ and Na+ ions of a system of monovalent feed and monovalent driving ions, and remained constant at 175 for a system of bivalent feed and bivalent driving ions. The flux of ions was scarcely affected by the kinds of co-ions. It was necessary to pretreat the membrane with driving ions.
