Lithium recovery from lithium-containing micas using sulfur oxidizing microorganisms

- Acidophilic microorganisms lower the pH from 5 to 1.5 by oxidizing elemental sulfur.
- About 26% lithium and 24% gallium extraction from lithium mica during bioleaching.
- A final lithium concentration of 150 mg/L was obtained.

There is about 60,000 t of lithium mica in the German part of the deposit in the Erzgebirge mountains. Lithium can be recovered by high pressure-high temperature leaching with sulfuric acid and further hydrometallurgical processing. Another idea, developed in the EU-project FAME, was to use sulfur oxidizing microbes to produce sulfuric acid and to extract lithium at moderate temperature and pressure conditions. Experiments were carried out in 2 L and 4 L batch reactors at 30 °C. After microbial transformation of elemental sulfur to sulfuric acid, the milled (<45 µm) lithium mica was added at a pulp density of 5%. Up to 26% of lithium was extracted biologically compared to 16% by chemical leaching. The bioleaching solution contained about 1 g/L aluminium, 0.8 g/L iron and 0.2 g/L lithium and could be further processed hydrometallurgically.