Acid Leaching Extraction Mechanism of Aluminum and Iron Ions from Coal Gangue Based on CaF₂ Assistance and Process...

To reveal how CaF₂ improves the dissolution ratios of aluminum and iron ions in coal gangue, CaF₂ and hydrochloric acid are used to extract Al³⁺ and Fe³⁺ from the coal gangue calcined powder. The leaching ratios of Al³⁺ and Fe³⁺ are measured, and the filter residues are analyzed by BET, XRD, and SEM. The results show that adding 3% CaF₂ could increase the extraction ratio of Al³⁺ from 62.96% to 92.10% under optimized conditions, and that of Fe³⁺ is increased from 85.12% to 95.73%. The mechanism of CaF₂ as an auxiliary to improve the leaching ratio of Fe³⁺ is that HF reacts with the thin layers of gangue calcined powder containing silica to form soluble SiF₄, thus forming pores that promote the diffusion of H⁺ and inner ions, improving the leaching ratios of Al³⁺ and Fe³⁺. Finally, the CaF_2-assisted acid leaching process is optimized. The results showed that it is efficient and feasible to extract Al³⁺ and Fe³⁺ with the assistance of CaF₂ and that HF has a catalytic effect in the reaction system. This work provides a reference for the next step of actual production.