Metso Develops Direct Leach Process for Battery-Grade Lithium Salts

Metso Oyj has unveiled its alkaline leach concept, a proprietary hydrometallurgical technology for refining spodumene concentrates into battery-grade lithium salts. The Metso Lithium Hydroxide Process is presented as a direct leach method that avoids the use of sulfates and acids, aiming for reduced environmental impact compared to conventional sulfuric acid roasting and caustic conversion techniques.

The developed process extracts lithium from silicate minerals through pressure leaching, followed by a conversion step to solubilize the lithium. This results in a lithium-rich solution and a mineral residue, primarily analcime, which Metso states is inert and easily neutralized. The company reports that the alkaline environment ensures selective lithium extraction with low solubility of impurities, achieving lithium recovery rates typically exceeding 90% from concentrate to washed residue.

Metso has conducted testing and pilot operations with various spodumene concentrates, successfully producing battery-grade lithium hydroxide monohydrate (over 56.5% LiOH·H2O) and lithium carbonate (over 99.5% Li2CO3). The company highlights that the alkaline leach concept is under development for other hard rock lithium minerals, including petalite, zinnwaldite, and lepidolite.

The company utilizes its proprietary OKTOP® reactors and Larox® filters within the process to ensure its performance. Metso emphasizes benefits such as an acid and sulfate-free leach, inert mineral residue, and reduced impact on air, water, and soil.