Reactor and column leaching studies for extraction of copper from two low grade resources: A comparative study

- Development of a process flowsheet for the recovery of copper from two different low grade sulphide resources.
- Comparison of different hydrometallurgical processing routes such as column /bioleaching and reactor leaching routes.
- Reactor leaching route gives a maximum recovery of 91% whereas 70% recovery is achieved through heap leaching route.
- Smooth and bright deposits of copper metal are produced with a purity of 99.9%.

Two ore samples, one obtained from a partially leached heap with suspended operations for about four years and the other through sonic drilling of a discarded dump were tested for the amenability/feasibility of copper extraction through reactor and column leaching. Mineralogical analysis of the samples indicated the dominant sulphide minerals to be chalcopyrite and pyrite. Various process parameters such as the effect of acid concentration, time, oxidant, pulverization and temperature were studied for the reactor leaching experiments. A maximum of 91% Cu extraction can be achieved while leaching the pulverized sonic drilled sample at 90 °C for 3 h. On the other hand, column leaching studies at 1 kg scale showed 65-70% Cu extraction with an acid concentration of 2.7% (v/v) for both the samples. Sequential leaching of the chemically leached residues of both sonic drilled and heap leached pad sample yielded additional 13.2% and 22.2% Cu, respectively in 20 days of bacterial leaching using a mixed culture of meso-acidophilic bacterial consortium. Column leaching studies showed that the heap leached pad sample was more amenable to leaching than the sonic drilled one. Further, during the downstream processing of the leach liquors, the solvent extraction efficiency was about 95% and the Cu metal deposited by electrowinning was of 99.9% purity. A tentative process flowsheet for the recovery of copper was also prepared.