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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).

The paper presents the results of a study on the simultaneous electrooxidation of cyanides and recovery of copper as a metallic deposition on the cathode from weak concentration rinse wastewater in an electrochemical reactor with a Ti/Pt anode. Both a direct electrooxidation process and an indirect electrooxidation in a chloride-rich medium proved feasible, with direct electrooxidation being preferable because of the lower energy consumption. The results show that the process of the direct electrooxidation under alkaline conditions leads to the formation of an electrocatalytic film on the anode. Simultaneous copper electrodeposition on the cathode is feasible and economically convenient, particularly if conducted at pH 13 or higher. The process can be described by the pseudo-first-order kinetics, with the rate constant for Cu removal equal to 0.013 h -1 for very alkaline conditions. Energy consumed for copper electrodeposition proved to be inversely proportional to the initial Cu concentration. For wastewater bearing 1100 mg dm -3 Cu, 5.46 kWh is needed to eliminate 1 kg of metal. The current efficiency for chemical oxygen demand removal reaching 100% or higher was obtained, indicating reactions other than electrooxidation occurring simultaneously. Under the best conditions, the total cyanide concentration was lowered from 250 to 7.9 mg dm -3 .