Extraction of lithium from coal gangue by a roasting-leaching process

Lithium is an important strategic metallic element, which plays a vital role in the production of batteries. Coal gangue has been regarded as a promising resource of lithium. In this study, the coal gangue collected from Jungar coalfield contains 437 ppm of lithium, which is significantly higher than the average content of coal (31.8 ppm) in China. Lithium extraction from the coal gangue was systematically investigated via the integrated process of roasting and acid leaching with the mechanism analysis. The majority (94%) of lithium was extracted when raw samples are roasted at 400°C for 20 min before 4 h leaching with 2 mol/L hydrochloric acid at 60°C, which represented the optimal conditions. X-Ray Diffraction patterns and surface microscopic analysis of the roasting samples showed that thermal decomposition of kaolinite, as the carrier minerals of lithium in the gangue, happened during the roasting, resulting in the easy release of lithium by acid leaching. It was found that diffusion is the dominant control factor of lithium leaching based on the kinetic analysis. In this paper, an integrated process of roasting and leaching with moderate conditions was developed and performed for lithium extraction from coal gangue.