| Summary: | 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.
|
|---|
