Electrodialytic separation of potassium ions from sodium ions in the presence of crown ether using a cation-exchange membrane

The separation of potassium and sodium ions from their mixture was performe d by electrodialyzing a mixed solution of potassium chloride and sodium chl oride in the presence of 18-crown-6 using a commercial cation-exchange memb rane. After 18-crown-6 had been impregnated in the membrane, the mixed solu tion containing 18-crown-6 was electrodialyzed as the desalting-side soluti on. The permeation of potassium ions through the membrane decreased remarka bly and the electrical resistance of the membrane increased during electrod ialysis with increasing concentration of 18-crown-6 in the solution. Becaus e cations, cations, potassium ions form a more stable complex with 18-crown -6 than sodium ions and because the complex permeated through the membrane with difficulty, sodium ions are thought to selectively permeate through th e membrane. The current efficiency in electrodialysis was greater than 97.0 %.