An investigation of the electrowinning of copper with dimensionally stable titanium anodes and conventional lead alloy anodes
Msindo, Zvanaka Senzeni
The traditional anodes of choice in the electrowinning industry have been lead based anodes. However, these anodes display high energy consumption and low corrosion resistance during operation. These problems led to the investigation of other anode materials such as dimensionally stable anodes (DSAs), consisting of mixed metal oxide coatings on titanium or nickel substrates. In this study, electrochemical tests, physical characterisation techniques and electrowinning of copper from synthetic and industrial electrolytes were carried out on DSAs and lead anodes. These tests focused on stability, energy consumption and copper deposit quality. Potentiodynamic polarisation showed that the DSA plate anode exhibited the highest corrosion resistance while, lead and DSA mesh anodes showed spontaneous passivation in a synthetic solution. These anodes are therefore likely to succumb to failure earlier than the DSA plate anode. Lead anode dissolution was observed in galvanostatic chronopotentiometry tests. It was also observed that the failure mechanism of DSA anodes involves coating loss. In electrowinning tests, copper deposits from the lead anode cell showed the presence of lead oxide. Furthermore, it was observed that, despite both mesh anodes (DSA 1 and DSA 2) exhibiting the lowest total energy consumption, they had the highest energy consumption per kilogramme of copper produced. The DSA 1 plate anode had the greatest current efficiency and therefore had the least energy consumption per kilogramme of copper. It was also noted that DSA anodes of the same composition may exhibit different behaviours as this depends on the method of preparation of the anode itself. The presence of iron or manganese in the electrolyte affected cathode quality, current efficiency, led to voltage fluctuations and an increase in anode potentials.