Stirred-tank reactor bioleaching of nickel and cobalt from Brazilian laterite ores

Laterite ore deposits in Brazil and other tropical countries harbor large amounts of nickel and cobalt resources, along with other critical raw materials. The conventional methods of recovering nickel and cobalt, such as pyrometallurgy or high-pressure acid leaching, entail high energy, reagent costs, and expensive equipment. To address this, the German-Brazilian project BioProLat aims to develop an integrated, low-energy, and environmentally friendly biohydrometallurgical process for metal recovery from Brazilian laterite ores.

The process involves leveraging acidophilic bacteria that use sulfur as an electron donor, coupling sulfur oxidation to the reduction of ferric iron, ultimately converting insoluble metal compounds into water-soluble forms. This generates sulfuric acid, creating the necessary acidic conditions to keep iron and other metals soluble. Laboratory-scale bioreactor experiments optimized parameters like pH, temperature, and a suitable bacterial consortium for bioleaching nickel and cobalt. Results from aerobic bioleaching of laterite with a consortium of Acidithiobacillus thiooxidans strains showed an extraction of 85% for both cobalt and nickel. Mineralogical and geochemical analyses were conducted to identify mineral phases, which are attacked by bioleaching, and estimate the portions of cobalt and nickel released by bioleaching of different mineral phases. The goal is to scale up the optimized process, converting untapped ores and limonite stockpiles into valuable resources and unlocking new raw material reserves by enhancing metal recovery from existing mines.