METHOD FOR RECOVERING METAL FROM WASTE CYANOGEN LIQUID

PURPOSE:To deposit the metals contained in the metal-contg. waste cyanogen liquid discharged from a plating factory to a cathode to recover said metals and to converting the harmful cyanogen ions to a harmless material by oxidation decomposition by subjecting the above- mentioned waste liquid to an electrolytic treatment in an electrolytic cell where a fluorine contg. anion exchange membrane is used as a diaphragm. CONSTITUTION:The electrolytic cell 1 is divided to a cathode chamber 2 and an anode chamber 4 by the fluorine contg. anion exchange membrane 6 made of the copolymer consisting of the repeating unit expressed by formula [I]. The cathode 3 made of granular or fibrous carbon or the like which is insoluble in aq. KCN soln. and has a large surface area is disposed in the chamber 2 and the anode 5 made of a metal such as Ti, Ta, Zr, Nb, etc., likewise insoluble in the aq. KCN soln. or formed by coating such metal surface with Pt, Ir, Rh, etc., is disposed in the chamber 4. The aq. KON soln. is supplied into the chamber 4 and the waste plating liquid contg. the plating metals and KCN is supplied into the chamber 2. The electrolytic treatment is executed by a DC power source 7. The metallic ions in the waste plating liquid are deposited and recovered on the surface of the cathode 3, and the CN ions migrate from the chamber 2 through the membrane 6 into the chamber 4 and are oxidation-decomposed by the anode 5, by which said ions are converted to harmless material.