AlCl3⋅6H2O recovery from the acid leaching liquor of coal gangue by using concentrated hydrochloric inpouring

Abstract

Alumina extraction from coal gangue is hopeful to solve the stockpile and pollution problems of it in China. The impurities such as Fe, Ca, K and Mg in coal gangue would be dissolved in the acid leaching liquor in the process of alumina extraction using hydrochloric acid leaching, resulting in the difficulty in the separation of Aluminum. AlCl3⋅6H2O recovery from the recycled AlCl3-containing acid leaching liquor of coal gangue by concentrated hydrochloric acid inpouring was discussed in this paper. It showed that the saturated AlCl3 solution or leaching liquor presented high recovery and the maximum reached more than 80% at <45°C. The recovery increased with increasing the volume of concentrated HCl. It reached >85% of the maximum crystallization at the volume ratio of concentrated HCl to the solution exceeding 2.25. The effect of the recycled crystallized liquor on the comprehensive dissolution of alumina is negligible. The contents of Al and levels of impurities such as Fe, Ca, K and Mg in the leaching liquor increased with the cycles, which had a significant effect on the recovery and quality of AlCl3⋅6H2O. The recovery of AlCl3⋅6H2O decreased gradually with the cycles and it decreased to 59.5% after 10th cycle. The contents of AlCl3⋅6H2O in crystals decreased since the levels of impurities in it increased with the cycles, which would limit the cycle times of the crystallized liquor.