Abstract: Spent aqueous hexavalent chromium solutions containing trivalent chromium ions and extraneous metal ions are oxidized by placing said exhausted Cr.sup.+6 solution in the anode compartment of an electrolytic cell as the anolyte, said cell being separated into anode and cathode compartments by at least one cation selective membrane, said cathode compartment containing a catholyte, and impressing a direct current across the anode and cathode of said cell of a difference in potential sufficient to promote the oxidation of trivalent chromium in the solution in said anode compartment to hexavalent chromium while extraneous metal ions in the anolyte solution migrate through said membrane into the catholyte of said cathode compartment where copper ions are plated onto said cathode. The anode compartment consists of a removable and portable container consisting essentially of a framework having side members secured thereto, at least one of said anode members comprising a cation selective membrane.

Abstract: Exhausted Cr.sup.+6 oxidizing solutions containing Cu.sup.+2 values are electrolyzed by placing an exhausted Cr.sup.+6 etching or oxidizing solution containing copper ion and Cr.sup.+3 ions in an electrolytic cell containing at least one pair of carbon particle electrodes, and forcefully flowing the exhausted solution through the electrodes and simultaneously impressing a direct current across the electrodes such that at the cathode divalent copper is reduced to copper metal and Cr.sup.+6 values are reduced to trivalent chromium and at the anode water is oxidized to oxygen.