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 electrooxidat ion of cyanides and recovery of copper as a metallic deposition on the cath ode 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 ele ctrooxidation being preferable because of the lower energy consumption. The results show that the process of the direct electrooxidation under alkalin e conditions leads to the formation of an electrocatalytic film on the anod e. Simultaneous copper electrodeposition on the cathode is feasible and eco nomically convenient, particularly if conducted at pH 13 or higher. The pro cess can be described by the pseudo-first-order kinetics, with the rate con stant for Cu removal equal to 0.013 h(-1) for very alkaline conditions. Ene rgy consumed for copper electrodeposition proved to be inversely proportion al to the initial Cu concentration. For wastewater bearing 1100 mg dm(-3) C u, 5.46 kWh is needed to eliminate 1 kg of metal. The current efficiency fo r chemical oxygen demand removal reaching 100% or higher was obtained, indi cating reactions other than electrooxidation occurring simultaneously. Unde r the best conditions, the total cyanide concentration was lowered from 250 to 7.9 mg dm(-3).