The Preparation of Divalent Cation Non-permselective Cation Exchange Membrane by Coating with Vinylon Film

Abstract

The preparation of non-permselective membrane for the divalent cation was attempted by coating it with thin vinylon film on one side of a commercial cation-exchange membrane. When the coating surface of the cationexchange membrane was set on the concentration-compartment side (cathode side), the permselectivity coefficient of the calcium ion to the sodium ion was equal to that of untreated cation-exchange membrane and no effect of the selective treatment was recognized. However, when the coating sufrace was directed to the desalting-compartment side (anode side), an effect of the selective treatment was observed; in this case, the permeability of the calcium ion was more depressed, corresponding with the formalation degree of the selective-treatment membrane; for example, the permselectivity of the calcium ion for the membrane which was formalated for 180 min at 30°C decreased about one half compared with the untreated membrane. The electric resistance of the cation-exchange membrane increased upon the coating with the vinylon film, and especially the resistance of the calcium ionic-form membrane indicated a remarkable increase.

Selectivity of Transport of Sodium, Magnesium, and Calcium Ions through a Sulfo-Cationite Membrane in Mixtures of Solutions of Their Chlorides

“…For example, as follows from the data reported in [2], the coefficients of the selectivity of transport of ions of magnesium and calcium relative to transport of ions of sodium sharply increase at currents below 1 A dm -2 . At the same time, as follows from the data reported in [1], the coefficient of the selectivity of transport of ions of calcium relative to transport of ions of sodium somewhat decreases following a decrease in the current density from 2.5 A dm -2 practically to zero. The aim of this work is to investigate the transport numbers and the selectivity of transport of sodium, magnesium, and calcium ions through a cation-exchange membrane in solutions of chlorides of sodium, magnesium, and calcium and their mixtures and especially the effect the current density exerts on these properties.…”

“…At current densities that exceed 1 A dm -2 , the selectivity coefficient ( = 1.06), which was calculated with formula (3), is close to the experimental values. 1 On the other hand, at current densities below 0.5 A dm -2 , i.e. substantially below the limiting value, the transport numbers for magnesium ions, as opposed to those presented in Fig.…”

“…These data are presented for example in [1][2][3][4][5][6][7] and are frequently controversial. For example, as follows from the data reported in [2], the coefficients of the selectivity of transport of ions of magnesium and calcium relative to transport of ions of sodium sharply increase at currents below 1 A dm -2 .…”