Evaluation of leaching parameters for dissolving Ni and Co from chromite overburden using acidophilic bacterial consortium

The chromite mine of Sukinda Valley located in the Indian state Odisha produces a large amount of overburden during the mining of chromite ore. The overburden waste contains different valuable metals with very low concentrations. Its environmental metal leaching contaminates nearby water resources, which creates serious chaos in the local communities. However, the presence of Ni-oxide in the overburden makes it the only Ni resources of India. Therefore, an experimental attempt was made to evaluate the possibility of Ni recovery from the overburden. The physico-chemical analysis of the overburden sample showed that it contains 0.89 and 0.031% (w/w) of Ni and Co, respectively, which remain embedded within the goethite matrix. Bioleaching may be suitably applied to it. Therefore, bioleaching of Ni and Co from the overburden sample was conducted using an acidophilic bacterial consortium. Effect of leaching parameters like contact time, initial pH, temperature, Fe(II) addition, and pulp density was evaluated. Bioleaching of the overburden sample using the acidophiles was found to be effective. Further, all the leaching parameters showed positive effect on the bioleaching efficiency.