Influence of lead dioxide surface films on anodic oxidation of a lead alloy under conditions typical of copper electrowinning

Abstract

Cyclic voltammograms, current transients at constant potential and potential decay transients have been used to study the formation of lead dioxide surface films in the presence of cobalt ions and their role in decreasing the oxidation rate of a lead alloy under steady state conditions typical of copper electrowinning. The observations in the present work indicate, consistent with the surface film model, that the formation of a continuous PbSO 4 + a-PbO 2 film on the surface of the lead alloy in the presence of cobalt ions hinders further oxidation of the metal. The protectiveness of the film is dynamic in the steady state; the film is continuously forming and dissolving. Also studied was the potential of the oxygen evolution reaction on aPbO 2 and b-PbO 2 in 170 g L -1 H 2 SO 4 with and without cobalt ions. The steady state potential for oxygen evolution on b-PbO 2 in 170 g L -1 H 2 SO 4 at 285 A m -2 decreased in the presence of cobalt ions and the steady state potential of b-PbO 2 was essentially the same as that of (i) the Pb-CaSn alloy and (ii) a-PbO 2 . The implication is that the potential of the Pb-Ca-Sn alloy is determined by the a-PbO 2 and/or b-PbO 2 on its surface.

Electrochemical impedance spectroscopy evaluation of behaviour of Pb–Ag anodes for zinc electrowinning

“…This shows a spontaneous transformation of lead dioxide into lead sulphate because thermodynamically lead dioxide is unstable on the surface of lead in the sulphuric acid solution. 20 According to Zhang et al , a longer plateau for Pb–0·56Ag anode means a higher dissolution rate during the decay due to the presence of more important corrosion products during electrolysis. 9…”

“…It is admitted that b-PbO 2 is a better microstructure for oxygen evolution. 20 Moreover, it can be observed from Table 2 that the charge transfer resistance and the apparent double layer capacitance increase with polarisation time. It is admitted that the more Ag in Pb-Ag anode leads to less PbO 2 , less corrosion rate and higher values of R ct .…”

Electrocatalytic Activity of Pd/Ir/Sn/Ta/TiO2 Composite Electrodes

“…Unlike developed countries, however, developing countries fail to achieve efficient resource use through recycling, as their recycling processes are not technologically advanced nor industrialized. Among the various types of recycling, electrowinning (electrolytic refining) is typically very energy efficient [1][2][3][4][5].…”