Enhanced Photoelectrocatalytic Decomposition of Copper Cyanide Complexes and Simultaneous Recovery of Copper with a Bi2MoO6 Electrode under Visible Light by EDTA/K4P2O7

Simultaneous photoelectrocatalytic (PEC) oxidation of cyanides and recovery of copper in a PEC reactor with a Bi2MoO6 photoanode was investigated at alkaline conditions under visible light irradiation. The surface variation of the Bi2MoO6 photoanode and titanium cathode was characterized. The Cu mass distribution onto the anode, in the solution, and onto the cathode was fully investigated. In the individual PEC oxidation of copper cyanides, the formation of a black copper oxide on the anode occurred. By keeping the initial cyanide concentration at 0.01 mM, the effect of EDTA/K4P2O7 was examined at different molar ratios of EDTA/K4P2O7 to cyanide. It was indicated that the oxidation of cyanides increased and simultaneous copper electrodeposition with zero value onto the cathode was feasible at pH 11. Under the optimal conditions, the total cyanide concentration was lowered from 250 to 5.0 mg/L, and the Cu recovery efficiency deposited onto the cathode was higher than 90%. Cyanate was the only product. The role of the photogenerated hole in the oxidation of cyanide ions was confirmed.