Separation and Recovery of Valuable Carbon Components and Li/Ga Metals in Coal Gangue by Using a Flotation Flowsheet

Coal gangue (CG), an industrial solid waste with high contents of Li and Ga, has attracted the attention of researchers. However, the utilization of CG remains an economic challenge. Pre-enrichment of Li and Ga by flotation was carried out with a view to improving the comprehensive utilization of CG. Mineral composition, time-of-flight secondary ion mass spectrometry (TOF-SIMS), and elemental composition were used to investigate the embeddedness of each mineral and the mode of elemental occurrence in the CG. The results showed that the main mineral compositions of the CG were kaolinite, quartz, and pyrite. Li and Ga were mainly associated with kaolinite and other clay minerals. Li and Ga had a high correlation with Al₂O₃ and SiO₂, while Li and Ga were highly correlated with SiO₂/Al₂O₃, indicating that Li and Ga may be associated with one or more high-alumina minerals. In addition, flotation tests proved that synergistic sorting of ash impurities and valuable components from the CG was a cost-effective method. The ash content of the final product was increased by 3% under the process of prediscarding concentrate-dissociation-secondary flotation, and the contents of Li and Ga in the final product were also slightly enriched, and the recovery rate of the carrier minerals of Li and Ga can reach 66.1%.