Bioleaching of nickel and cobalt from laterite ores in Brazil: A reactor-based approach

Laterite ore deposits in Brazil and other tropical countries house substantial nickel and cobalt resources, as well as other vital raw materials. Traditional methods for extracting nickel and cobalt, such as pyrometallurgy or high-pressure acid leaching, come with significant downsides, including high energy usage, reagent expenses, and the necessity for costly equipment. To tackle these challenges, the German-Brazilian project BioProLat aims for an integrated, low-energy, and environmentally friendly biohydrometallurgical process for extracting metals from Brazilian laterite ores.

The process involves harnessing acidophilic bacteria that use sulfur as an electron donor, linking sulfur oxidation to the reduction of ferric iron. This transformative mechanism converts insoluble metal compounds into water-soluble forms. Consequently, sulfuric acid is produced, creating the essential acidic conditions to maintain the solubility of iron and other metals. Laboratory-scale bioreactor experiments were done with varying parameters such as pH, temperature, and the selection of a suitable bacterial consortium for optimal bioleaching of nickel and cobalt. Notably, aerobic bioleaching of laterite with a consortium of Acidithiobacillus thiooxidans strains achieved a maximal extraction of 85% cobalt and 85 % nickel from a laterite ore sample. Comprehensive mineralogical and geochemical analyses were conducted to identify mineral phases susceptible to bioleaching and estimate the proportions of cobalt and nickel released from various mineral phases. The overarching objective is to upscale the optimized process, transforming untapped ores and limonite stockpiles into valuable resources while unlocking new reserves of raw materials through enhanced metal recovery from existing mines, including economic and environmental evaluation.