Concentrating rinse water in plating solution by electrolysis with ion-exchange membrane was studied using various kinds of cyanide plating solution watered 10 times as dilute as the original.
Result:-
1. Concentration-ratio of each constituent in the diluted zinc cyanide solution is higher in order of OH^-, CN^- and Zn ion.
2. Concentration-ratio of each ion in the diluted silver cyanide solution is higher in order of CN^-, Ag(CN)₂^- and CO₃^--.
3. In the concentration of diluted copper cyanide solution, the concentration-ratio of Cu(CN)₃^-- is greater than that of free CN^-.
4. Current efficiency of ions entering concentration chamber through ion-exchange membrane is 60.3-73.3% when the membrane CMG 10 and AMG 10 is used, and 33.5-46.6% when the membrane CMG 20 or AMT 20 is used.
5. As electrolysis proceeds, the movement of water through the membrane gradually outdoes that of irons, so that the total gram-molar concentration-ratio arrives at the maximum value showing no further increase. The maximum value is 5.15 for diluted zinc cyanide, 12.26 for diluted silver cyanide and 10.46 for diluted copper cyanide solution respectively.