Selective separation of copper and cadmium from zinc solutions by low current density electrolysis

Copper and cadmium ions were selectively separated from zinc sulphate aqueous solution or zinc ammonia/ammonium sulphate aqueous solution by low current density electrolysis. It was shown that the concentration of cadmium ion in zinc sulphate solution decreased from 4.56 g/L to 0.18 g/L in an electrolysis time of 8.5 h, whilst it decreased from 5.16 g/L to lower than 0.005 g/L in zinc ammonia/ammonium sulphate aqueous solution. On the other hand, the deposition rate of copper was so low that it was difficult to separate copper and cadmium ions from the zinc ammonia/ammonium sulphate aqueous solution during electrolysis. But copper ion could be decreased to 0.002 g/L in this solution through solvent extraction by using kerosene diluted LIX984N as extractant. Therefore, it is favorable to recover cadmium ion from the zinc ammonia/ammonium sulphate solution by electrolysis after solvent extraction of copper.