Comparing the extent of the dissolution of copper-cobalt ores from the DRC Region
S Stuurman, S Ndlovu, V Sibanda
Inorganic acids such as sulphuric acid have found use together with
certain reducing agents in leaching of copper-cobalt oxide ores. These
reagents are not ideal due to the adverse effect the inorganic acids
generally have on the environment and the high costs of the reducing
agents. In this study a copper-cobalt oxide ore from the Central
African Copperbelt was leached in two different environments;
sulphuric acid in conjunction with hydrogen peroxide as a reducing
agent and tartaric acid. The effects of acid concentration, reducing
agent concentration, and temperature were independently determined
for both leaching environments. The sulphuric acid concentration was
varied between 0.4 M and 1.2 M and the concentration of hydrogen
peroxide between 4.0 M and 6.5 M, while the tartaric acid concentration
was varied between 0.15 M and 0.35 M. The temperature was
varied between 20°C and 50°C. The results showed that the extraction
of both copper and cobalt increased with sulphuric acid concentration,
reaching a peak at approximately 0.8 M and then decreasing
at higher acid concentrations. A similar increase and decrease in
metal extraction was observed when the reducing agent was
increased. In leaching with tartaric acid, the extraction of cobalt was
much higher than that of copper, although extraction of both metals
increased with acid concentration. Additions of small amounts of
hydrogen peroxide were found to increase cobalt extraction in tartaric
acid but had a minimal effect on copper. An increase in the solution
temperature had a significant effect in the organic acid environment,
with the effect on cobalt extraction being much more pronounced
than on copper.
Keywords: leaching, copper, cobalt, sulphuric acid, hydrogen peroxide, tartaric
acid, reducing agent.