Leaching of cobalt anode sludge for the production of cobalt metal using sodium sulphate as a reductant.

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Malizhi, Davie M.
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During electrowinning in the Nkana cobalt tank house, sludge is formed from the anodes and it is periodically collected from the cells and stored. The sludge contains appreciable amount of cobalt which is not recovered at the moment. It is for this reason that the project was proposed to investigate the possibility of recovering cobalt metal from the sludge. Therefore, the objective of this study was to establish the potential of recovering cobalt metal from the anode sludge by determining the dissolution rate of cobalt metal as a function of pH, redox potential and temperature. Leaching experiments were conducted using sulphuric acid as a leachant and Sodium Sulphite as a reductant to reduce the Co3* and for redox potential control in the cobalt anode sludge pulp to a readily leacheable Co2*. From the results, highest leach efficiencies of 52.27% cobalt at the pH of 2.0 and 68.6% at the temperature of 60°C were obtained. It can be concluded that cobalt is potentially teachable from the anode sludge but there is need to conduct more tests in order to increase the leach efficiencies. It is recommended that further tests should be done such as observing the effects of leachant concentration and use of other reductants on leaching efficiency as well as the mineralogical examinations to identify the other elements/compounds present in the cobalt anode sludge to optimise the leach efficiency.
Cobalt ores , Cobalt industries