Factors affecting copper solubility in electroplating waste

Diluted plating solutions collected from electroplating shops were subjected to bench-scale chemical destruction and alkaline precipitation, and copper solubility in treated wastes was measured from pH 8 to 12. 5 for initial copper concentrations of 50, 200, 500 and 1000 mg/l. Copper solubility in treated copper cyanide plating solutions increased as the initial copper concentration increased, and was much higher than in comparable laboratory-prepared copper sulfate solutions. The pH of minimum copper solubility was 1 to 20 pH units higher in the treated copper cyanide plating solutions. Addition of other plating solutions to copper cyanide solutions increased copper solubility.