Kinetics of alumina extraction from coal gangue by hydrochloric acid leaching

The leaching kinetics of alumina extraction from coal gangue with hydrochloric acid was investigated. The effects of calcination activation temperature and leaching conditions on the alumina extraction efficiency were studied. The results revealed that the alumina extraction efficiency can reach 91.56% under the following optimum conditions: a calcination temperature of 700 °C, dissolution at 150 °C for 2 h in hydrochloric acid with a concentration of 20%, and a liquid-to-solid ratio of 3:1. Notably, lithium was leached simultaneously with alumina, and its leaching rate reached 80.00 %. The leaching of alumina followed the shrinking unreacted core model, and the process was controlled by a chemical reaction, with activation energy of 45.64 kJ/mol.