Two inorganic materials were prepared by calcination-acid leaching combined treatment of coal gangue: Al&Fe enriched acid solution and Si enriched material

The classification and extraction of valuable components from coal gangue is a way to improve the comprehensive utilization of coal gangue. However, the stable structure of kaolinite in coal gangue makes silicon and aluminum closely combined in minerals, which is difficult to separate by simple physical or chemical methods, and hinders its hierarchical extraction. In this study, a method of calcination activation acid leaching combined with reduction treatment of coal gangue was developed, and an aluminum iron enriched acidic solution and a silicon enriched material were prepared. The activation effect and mechanism of calcined coal gangue and the conversion mechanism of acid leaching extraction of metal aluminum were systematically studied. The results showed that the optimal calcination activation acid leaching process parameters were as follows: calcination temperature: 600 ℃, calcination time: 4 h, acid leaching time: 2 h, solid–liquid ratio of activated coal gangue and hydrochloric acid solution (g:ml): 1:12. After calcination under the optimal conditions, the layered structure of Kaolinite was destroyed and some layered silicate minerals, Berlinite (AlPO₄), FeS, which were soluble in hydrochloric acid solution, were formed. These minerals are dissolved in hydrochloric acid solution and then separated by solid–liquid separation after reaction. An acidic solution rich in aluminum and iron and a material rich in silicon were prepared, which made the recovery of Al and Fe reach 90.84 % and 97.68 %, respectively. And the enrichment rate of Si (SiO₂) reached 83.90 %.This provides a new solution for the comprehensive utilization and sustainable utilization of coal gangue.