Recovery of copper (II) and chromium (III,VI) from electroplating-industrywastewater by ion exchange

Two laboratory-scale separation processes have been developed for the recov ery of copper (II) from acidic and cyanide-containing alkaline wastewater o f electroplating industries. Acidic bath wastes were treated with Dowex 50X 8, a strongly acidic cation-exchange resin, and the retained copper was elu ted with H2SO4. The cyanide-containing alkaline bath waste was first oxidiz ed with excessive hypochlorite, then neutralized, and recovered by the use of Amberlite IRC-718 chelating resin. Copper was eluted with H2SO4. The two different valencies of chromium have been recovered from electropla ting-industry wastewater by different separation processes: The predominant valency, Cr(VI), was retained on a strongly basic Dowex 1X8 resin and elut ed with a NaCl and NaOH solution. Alternatively, Cr(III), either existing o riginally in electroplating-industry waste-rinse mixtures or converted from Cr(VI) by reduction with Na2SO3, could be recovered by a weakly acidic Amb erlite IRC-50 resin and eluted with a solution containing H2O2 and NaOH. Wh ere plating industry wastes contain high levels of organic contamination, C r(VT) would be naturally reduced to Cr(DI) upon acidification, and it may b e more economical to recover all chromium as Cr(TII).