Biohydrometallurgy for Cobalt and Nickel recovery from laterites: project BioProLat

Laterite ore deposits in Brazil and other tropical countries contain approximately 70% of the world’s Ni and Co resources. High energy and/or reagent costs, accompanied by expensive equipment costs, are generally incurred when recovering Ni and Co via pyrometallurgy or high pressure acid leaching. Considering economic efficiency, the development of an integrated low-energy and environmentally benign biohydrometallurgical process for the recovery of these metals from laterite ores in Brazil is the aim of the German-Brazilian project BioProLat. Several acidophilic bacteria are able to use sulfur (S) as electron donor and couple the oxidation of S to the reduction of ferric iron, and are thereby capable of reducing the insoluble metal compounds to a water-soluble form. During this process sulfuric acid is generated, providing the acidic conditions that are needed to keep iron and other metals soluble. Stirred-tank bioreactor and percolation column laboratory experiments were used to optimize parameters including pH, temperature, aeration and a most suitable bacterial consortium for the bioleaching of Ni and Co. Stirred-tank laterite bioleaching at a start pH 1.5 under aerobic conditions with a consortium of different Acidithiobacillus thiooxidans strains resulted after 15 days in maximal 83 % extraction for both, Co and Ni, for 10 % (w/v) pulp density of a laterite sample from Barro Alto mine, Brazil. Eventually, the optimized process will be upscaled and reach pilot scale, transforming unexploited ores and limonite stockpiles into valuable resources, unlocking new reserves of raw materials through increasing recovery of metals from existing mines.