Copper electrodeposition and oxidation of complex cyanide from wastewater in an electrochemical reactor with a Ti/Pt anode

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).