Mineral leaching of non-sulphide nickel ores using heterotrophic micro-organisms

Laboratory studies were conducted on microbial leaching of non-sulphide nickel ores not amenable to conventional mineral processing operations. The results showed that extensive low-grade laterite domestic sources are generally amenable to bioleaching when micro-organisms were cultivated in the presence of the ore. Nickel recoveries were as high as 60% using hydroxycarboxylic acid producing strains of Aspergillus and Penicillium codes A3, P2. Cobalt recovery achieved was around 50%. Losses of soluble nickel in the fungal biomass were found to be 3.5–10.8%. Chemical analysis of the leach liquors showed the presence of significant amounts of citric, oxalic and other organic acids, indicating that leaching may be ascribed to the production of these metabolic products of fungal activity.