Increased demand for aluminium around the world is promoting interest in developing alternative technologies for producing aluminium oxide (alumina) from non-bauxite sources, especially from clay. The sulphuric acid decomposition of kaolin clay of the Chovdar deposit (Azerbaijan) has been investigated with the aim of aluminium recovery using the aqueous solution of sulphuric acid as a leaching agent. Before leaching, kaolin clay was calcined at a temperature of 700-750 °C for 2 h. This process involves dehydration of kaolinite, which is the main mineralogical phase of kaolin, and its transformation into metakaolin, an amorphous Al-Si structure from which aluminium is readily leached. The optimal conditions for iron oxide and aluminium oxide leaching by sulphuric acid have been determined, and the degree of recovery was determined for these metals. It has been revealed that kaolin clay leaching to extract aluminium and iron oxides is achieved using kaolin clay samples calcined under the above-mentioned conditions, by treating them with 40 % sulphuric acid for 120 min at a temperature of 95 °C. The degree of Аl2О3 and Fе2O3 extraction under these conditions is 95.6 and 85.2 %, respectively.
Efendiyeva et al. (Fri,) studied this question.