Aerobic Bioleaching of Six Brazilian Laterite Ores with Acidithiobacillus thiooxidans, Sulfobacillus species and Archaea at Various Conditions

Abstract

Abstract Biohydrometallurgical laterite processing was explored at laboratory scale in this study. The extraction of nickel, cobalt, and other metals from six different laterite ores from three Brazilian deposits was tested via bioleaching in 2 L stirred tank reactors under aerobic conditions with acidophilic, sulfur-oxidizing bacteria and archaea. The experiments were run with three different mixed cultures, either a consortium of six different Acidithiobacillus (At.) thiooxidans strains at 30 °C, of five Sulfobacillus species at 45 °C, or a consortium of Archaea at 60 °C. The At. thiooxidans consortium resulted in the far best bioleaching performance in case the pH was not kept constant at 1.5 by NaOH addition. This led to low pH values of even < 1 in some bioreactor runs at the end of the experiments, and a maximal extraction of 83% Co and 83% Ni for 10% (w/v) pulp density of a laterite sample from the Barro Alto mine after 15 days was achieved. Another sample achieved a similar high Co extraction but much lower Ni extraction with bioleaching by At. thiooxidans , whereas the third sample from Barro Alto (consisting of 98% iron(hydr)oxides) did not show increased Ni and Co extraction in comparison to the chemical control with the same pH. The two hematite-rich samples from the laterite deposit Jacaré and the silicate-rich sample from the deposit in Piauí behaved similarly to the iron-rich sample from Barro Alto. Overall, for laterite samples very rich in iron(hydr)oxides or silicates, the metal dissolution was only related to acid leaching (either chemical or biogenic sulfuric acid) because of a similar bioleaching and chemical leaching performance at the same pH each. In contrast, laterite samples with a more complex mineralogical composition could be processed efficiently via bioleaching with a reductive dissolution of mineral phases. Graphical Abstract

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