Electrochemical treatment of copper cyanide wastewaters using stainless steel electrodes

Abstract

A study was carried out to define the best conditions for the simultaneous electroxidation of cyanides and recovery of copper as a metallic deposition on the cathode from weak concentration rinse wastewaters, using plate stainless steel electrodes. A direct electroxidation process and an indirect electroxidation in a chloriderich medium were tested at pH from 10 to 13. The results show that the process of the direct electroxidation is feasible and economically convenient if conducted at pH 13. It was possible to reduce copper concentration from 470 mg−1 by 79% in 1.5 h, at an energy consumption of 17 kWh kg−1 and to recover 335.3 mg of Cu as pure metal, electrodeposited on the cathode. The CuO film formed simultaneously on the anode had catalytic properties for CN− electroidation. The efficiency of the destruction of cyanides was in the same order of magnitude, with kinetics being of first order with respect to cyanide concentration (first order reaction rate k = 0.007 min−1).