Cu-mediated optimization of PbO2 anodes for electrochemical treatment of electroless nickel plating wastewater

Abstract

Effective removal of Ni(Ⅱ)-organic complexes from electroless nickel plating wastewater remains a challenge by conventional industrial effluent treatment processes. In this study, electrochemical oxidation using a PbO2 anode is proposed for effective decomplexation of Ni-organic complexes. The electrode quality and electrocatalytic capability of the PbO2 anode is shown to be greatly affected by the nature of the PbO2 active layer that is formed during the electrodeposition process with the current density, cathode material and electrolyte constitutions all exerting an influence on the Pb deposition behavior. Our investigations reveal that the presence of Cu2+ in the electrolyte can precisely control the amount of elemental Pb formed with Pb cathodic reduction and deposition prevented as a result of preferential Cu0 deposition. The doping of PbO2 with Cu significantly improved the morphology and electrocatalytic performance of the PbO2 deposit. Ni-citrate and TOC removal percentages of 83 % and 55 % respectively were achieved with the optimal Cu-doped PbO2 anode with 73 % of the Ni recovered at the cathode at a relatively low specific energy consumption of 12.7 kWh m−3. A possible mineralization pathway of Ni-citrate by the PbO2 anodic oxidation process is proposed.