Selective extraction of lithium from coal gangue utilizing a two-stage roasting process

Abstract

With the discovery of super-enriched lithium (Li) in coal, coal-based Li resource is a promising way to meet Li demand. However, traditional Li extraction methods are mainly through acid leaching, bringing many impurities into leaching solution and complicating the subsequent purification process. Herein, a selective Li extraction method employing a sulfuric acid baking-decomposition process from coal gangue was proposed in this study, applying phase change strategy to prevent aluminum and iron impurities from entering the leachate. The feasibility of this process was confirmed through thermodynamic calculations, and then it was verified through experiments. Under the optimal conditions, the highest Li leaching rate reached 85.04 %, while Fe and Al were less than 0.5 %. XRD and SEM-EDS were employed to explore phase change process and mechanism, and the results indicated that minerals were converted to sulfate during the baking process and then decomposed into insoluble oxide during the second process, while Li₂SO₄ stayed stable and was separated through water leaching. This study provides a highly selective Li extraction process from coal gangue.