Modification of properties of ion‐exchange membranes. IV. Change of transport properties of cation‐exchange membranes by various polyelectrolytes

A change in electrodialytic transport properties of various cation exchange membranes was observed after the membranes had been adsorbed or ion‐exchanged with various cationic polyelectrolytes. Transport properties measured in this report were the relative transport number of calcium ion to sodium ion PCaNa, the current efficiency of cations, and the electric resistance of the membrane during the electrodialysis. Weakly basic and strongly basic cationic polyelectrolytes of various molecular weights were used. Though PCaNa of any cation exchange membrane decreased by the adsorption or ion exchange of any cationic polyelectrolyte, the degree of the decrease in PCaNa changed with species and molecular weight of polyelectrolytes and species of cation‐exchange membranes. Weakly basic polyelectrolytes and low molecular weight, strongly basic polyelectrolytes were effective in producing a marked decrease in PNaCa of any cation exchange membrane. The effect of strongly basic polyelectrolytes of high molecular weight on PCaNa was weak in most cases. However, if it was possible to make the polyelectrolyte adhere to the surface of the membrane to form a compact coiled structure, any cationic polyelectrolyte was effective in producing a remarkable decrease in PCaNa of any cation‐exchange membrane.