Studies on solvent extraction of copper and cyanide from waste cyanide solution

The recovery of copper and cyanide from waste cyanide solution with the guanidine extractant (LIX 7950) and the modified amine extractant (LIX 7820) has been investigated. Copper can be effectively extracted from alkaline cyanide solutions by both extractants. The free cyanide remains in the aqueous phase due to the preferential extraction of Cu(CN)32− over Cu(CN)43− and CN− by the extractants. The selectivity of the metals with the extractants under different cyanide levels has been examined. High cyanide levels tend to depress extraction of copper and silver cyanides, but exhibit insignificant effect on extraction of gold, zinc, nickel and iron cyanides. A possible solution to the separation of copper cyanides and free cyanide in cyanide effluents has been suggested, by which copper can be concentrated into a small volume of solution and the barren cyanide solution recycled to the cyanidation process.