Abstract:The alumina was efficiently extracted from prepared hydrogarnet through alkali-thermal transformation based on the efficient desilication product of hydroandradite. The effects of different parameters on alkali-thermal transformation of hydrogarnet and the reaction kinetics were systematically investigated. The results show that the prepared hydrogarnet is mainly formed by the aggregation of cubic particles, and its chemical composition is consistent with the standard molecular formula. The recovery efficiency of alumina increases by increasing the ratio of iron to alumina, enhancing the reaction temperature, prolonging the reaction time as well as increasing the molecular ratio. The recovery efficiency of alumina is 63.12% under the optimum conditions including the ratio of iron to alumina of 1, reaction temperature of 280 ℃, reaction time of 60 min, and molecular ratio of 30. Most of the hydrogarnet is converted to hydroandradite during alkali-thermal transformation. The reaction kinetics of alumina is controlled by interface transfer and diffusion across the product layer, and the apparent activation energy is 26.60 kJ/mol.