Kinetics of Pb and PbAg anodes for zinc electrowinning—I. Formation of PbSO4 layers at low polarization

✍ Scribed by C. Rerolle; R. Wiart

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 936 KB
• Volume: 40
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(95)00026-b

✦ Synopsis

Electrochemical impedance spectroscopy and scanning electron microscopy have been utilized to investigate the mechanism of reactions taking place on Pb and Pb-Ag alloy anodes in acidic zinc sulphate electrolytes, during the formation of PbSO, layers in the potential domain (0.9 to 1.1 V/SSE). Independent of the Ag content, the anode behaviour is essentially determined by the electrolysis time. From a comparison of experimental data to a kinetic model for the Pb/PbO,,/PbSO, electrode, it is shown that the layer growth is first controlled by the solid state diffusion of SOi-ions, and then by a chemical step associated with a change in charge carriers, from O:+ vacancies in the PbO, sublayer into Pb*+ ions in the PbSO, layer. In Mn2+ -containing electrolytes, the additional formation of MnO, occurs under diffusion control of the Mn'+ oxidation, and it modifies both the layer properties and the kinetics of reactions.