Abstract:For the low-grade gibbsitic bauxite, the leaching rate of alumina is very low during the Bayer process. The acid leaching method is attracting more attention, and the hydrochloric acid leaching was developed rapidly. The mineral composition and chemical composition were investigated by X-ray diffraction analysis and semi-quantitative analysis. The thermodynamics of leaching process was analyzed. The results show that the major minerals in the bauxite are gibbsite, secondly goethite and quartz, anatase and so on. The acid leaching reactions of the bauxite would be thermodynamically easy and completed. Under the conditions that ore granularity is less than -55 μm, the L/S ratio is 100:7, and the leaching temperature is 373-383 K, the leaching time is 120 min and the concentration of HCl is 10%, both the leaching rates of Al and Fe are over 95%. The main composition of leaching slag is SiO₂ which is easy for comprehensive utilization.

Key words: alumina; bauxite; gibbsitic bauxite; acid leaching; thermodynamics