Highly Selective and Green Recovery of Lithium from Coal Gangue Using Recyclable Ammonium Fluoride Leaching SystemHighly Selective and Green Recovery of Lithium from Coal Gangue Using Recyclable Ammonium Fluoride Leaching SystemXie, Han, Khan, Liang, Zhong, and He

With the discovery of super-enriched lithium (Li) in coal, coal-based Li deposit is a promising resource to meet Li demand. However, traditional Li extraction methods are mainly through acid leaching, which complicates the subsequent purification process. Herein, a method of selective lithium leaching employing recyclable ammonium fluoride (NH4F) was proposed. The influences of roasting temperature and leaching conditions were explored in detail. Under the optimal conditions, the Li leaching rate reaches 81.42%, while Fe, Al, Mg, Ca and Na are < 3%. Besides, NH4F could be generated and sent back into the leaching process. The roasting and leaching mechanisms assumed that kaolinite is transformed into metakaolinite after roasting. The Al-containing lattice structure is destroyed, and the Li residing in it is also released and becomes soluble Li, while other metal elements stay. This study provides a highly selective and green Li extraction process from coal-based Li deposits.