Co-utilization of spent pot-lining and coal gangue by hydrothermal acid-leaching method to prepare silicon carbide powder

Spent pot-lining from aluminum electrolysis and coal gangue are toxic and hazardous solid wastes with high recovery value and contents of valuable elements, such as carbon, silicon, aluminum and fluorine. Thus, harmless treatment and recycling of these materials are of considerable importance. For extracting valuable components, Spent pot-lining and coal gangue were co-treated by hydrothermal acid-leaching method in this study. Effect of adding spent pot-lining on impurities leaching rate of coal gangue was systematically studied, and results indicated that fluoride in spent pot-lining positively affected the decomposition of coal gangue. Moreover, effects of leaching temperature, initial acid concentration, time, and particle size, on the extraction efficiency of aluminum were investigated comprehensively. Optimum parameters obtained by single-factor test included reaction temperature of 200 °C, initial hydrochloric acid concentration of 10 mol/L, time of 10 h, liquid–solid ratio of 10:1, and particle size below 200 mesh. Under these conditions, leaching rate of aluminum reached to 92.47%. Acid-leaching residue was used in the preparation of silicon carbide powder by carbothermal reduction, and silicon carbide powder with small size (D50, the median diameter, of 18.15 μm) was obtained by firing the acid-leaching residue at temperature of 1600 °C for 5 h. This study provides an inspiring approach for recovering and reusing spent pot-lining and coal gangue.