Anodic behavior and microstructure of Pb-Ca-0.6%Sn, Pb-Co₃O₄ and Pb-WC composite anodes during Cu electrowinning

Plumbum-Wolfram Carbide (Pb-WC) and Pb-Co₃O₄ composite anodes were prepared by electrodeposition from a lead mathanesulfonate electrolyte for Cu electrowinning. By means of the cyclic voltammograms (CV) and Electrochemical Impedance Spectroscopy (EIS), the mechanism of the anodic processes playing on the surface of Pb-Ca-0.6%Sn, Pb-WC and Pb-Co₃O₄ composite anodes had been measured. Cyclic voltammograms analysis revealed the corrosion rate of the anodic layer in PbO₂ region. EIS analysis pointed out that the reaction kinetics varied a lot during electrolysis for it is a process indicating the formation and stabilization of anodic layer. At the very beginning of galvanostatic electrolysis, the reaction oxygen evolution (OER) was Pb to PbSO₄ and α-PbO₂. On the anodic layer after 24 h electrolysis, the more β-PbO₂ appears, and the adsorption resistance took a dominant part in the whole impedance. SEM observed the microstructures of the conventional Pb-Ca-0.6%Sn, Pb-WC and Pb-Co₃O₄ composite anodes before and after 24 h electrolysis, and X-Ray Diffraction (XRD) analysis showed the phase after 24 h electrolysis of the three anodes for Cu electrowinning. - Highlights: • WC and Co₃O₄ particles used as catalysts. • WC particles promote Pb to PbSO₄ and α-PbO₂ phase, Pb-Co₃O₄ particles promote Pb to β-PbO₂ phase. • WC particles are sheet and inlay into the lead crystal leading semi-crystal in Pb-WC composite. • Co₃O₄ particles adhere to the coating surface and control the growth direction of lead crystals. • Al matrix decreases the OER potential during copper electrowinning.