Outotec has carried out years of extensive R&D on the alkaline leach process concept for lithium extraction from beta-spodumene and has introduced the Outotec Lithium Hydroxide Process, a proprietary technology for refining spodumene concentrates. It offers a direct sulfate and acid-free method to produce battery-grade lithium hydroxide monohydrate from spodumene concentrates. The process is also environmentally sustainable as the residues are inert and easily neutralized.
The Outotec Lithium Hydroxide Process concept is based on a two-stage alkaline leach process. Lithium is first extracted from the silicate mineral in a pressure leaching stage using soda ash. The reaction involves the formation of soluble lithium carbonate and mineral component analcime (NaAlSi2O6·H2O) as the main components. In the second stage lithium carbonate is solubilized in a conversion reaction, producing lithium hydroxide solution and solid calcium carbonate, which will report together with other mineral residues. Lithium carbonate formed in hydrothermal leaching can be converted to lithium hydroxide in a fast reaction with high yields. Overall, the yield from concentrate for lithium leaching extraction typically exceeds 90%.
The alkaline hydroxide and carbonate processing milieu ensure very low solubilities of all the main impurity elements and compounds including Fe, Al, Mg, Ca, B, and P. No additional impurity removal or precipitation stages are needed. Lithium hydroxide PLS is a suitable feed for polishing with IX and further crystallization of the final LiOH monohydrate product.