Preparation of α-alumina particles from alunite ores by using dry caustic assisted roasting

In this study, the production of α-alumina particles from alunite ore was carried out through roasting-leaching and precipitation tests. The effects of parameters such as temperature, stirring speed, solid ratio, and leaching time on Al yield% were investigated in leaching tests using the response surface methodology (RSM) and central composite design (CCD). As a result of the experiments, the highest Al yield ratio as 86.06% was achieved in water leaching under conditions of 100°C, 900 rpm, 15% as solid ratio, and 65 min. as time after roasting at 600°C with NaOH. The experimental results revealed that temperature and solid ratio% were more influential than other parameters. To precipitate Al(OH)₃ from the loaded solution, HCl was used to reduce the pH. The precipitate was roasted in a muffle furnace at 1100°C (±50°C) for 240 min. Then, α-alumina particles were obtained with an efficiency of 89.89% and purity of 91.24%. The morphological properties of the final product were confirmed by TGA-DTA, SEM/EDX and X-ray diffraction analyses.