Recovery of lithium from coal gangue, with an emphasis on lithium occurrence, roasting pretreatment and leaching

Extracting lithium (Li) from Li-rich coal gangue achieves benefits of ecological protection, resource efficiency enhancement, and industrial upgrading. Employing TOF-SIMS, ICP-OES and SCEP methods, this study investigated Li-rich coal gangue from Southwest Guizhou, China, revealing that Li primarily occurs in an adsorbed state within kaolinite. Based on this, a “calcination-NaCl leaching” process was designed for Li recovery and a Li leaching rate of 93.66 % was obtained under optimal conditions. Mechanistic analyses combining pore characteristics, thermodynamic analysis, XRD, and TG-DSC indicated that during calcination, kaolinite undergoes dehydroxylation, dissociating its layered structure and forming a highly active amorphous phase. Concurrently, organic components like carbon and sulfur are effectively removed, creating a porous structure. This structural reconstruction significantly enhances the interfacial reactivity between kaolinite and NaCl solution, promoting the efficient release of Li⁺ through ion exchange. The findings provide a scientific reference for the high-value utilization of Li in coal-based solid waste.