Alumina Extraction from Kaolinite via Calcification-Carbonation Process

Abstract

The rapid development of the alumina industry in China has led to the depletion of high-quality bauxite resources. The proposed calcification-carbonation method (CCM) can convert the middle silicon of bauxite into CaO · SiO2 and CaCO3, thus enabling clean and efficient utilization of low-grade resources. Since kaolinite is the main silicon-bearing mineral in low-grade bauxite, the transformation characteristics of kaolinite in the CCM process are investigated in this research. The experimental results indicate that temperature has a significant effect on both the calcification process and the carbonation process. The theoretical alumina-to-silica ratio (A/S) in the reacted residue can be lowered to 0.55 using the CCM process used to treat gibbsite, resulting in a recovery ratio of alumina approximately 15% greater than that of the Bayer process. More than 65% of the alumina can be recovered through the CCM. The Na2O content in the slag from the CCM meets the requirements of the cement industry, and cleaner production of alumina can be enabled by the CCM.