Alumina Extraction from Kaolinite via Calcification-Carbonation Process

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 · SiO 2 and CaCO 3 , 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 Na 2 O 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.