چكيده به لاتين
Due to the decrease of high-quality bauxite resources, the exploitation of the capacity of low grade ores for alumina production has been considered. Using these ores in the conventional Bayer process leads to many problems due to the high content of silica. Exploitation of low-grade bauxite requires the use of efficient preprocessing methods (for use in the Bayer process) or the development of fundamentally different extraction methods. In this study, atmospheric leaching in both citric and oxalic acid was used to extract aluminum from low-grade bauxite ores of Jajarm mine. Calcination and mechanical activation processes were used as pre-leaching operations to increase dissolution. Preliminary experiments showed the superiority of oxalic acid over citric acid. Dissolution of crude bauxite in 1.5 M oxalic acid solution at 80°C temperature, solid to liquid ratio of 50 g/l and time of 6 hours, resulted in dissolution of 28.7% aluminum. Under similar leaching conditions, the dissolution efficiency of aluminum for calcined bauxite at 500℃ was 51.8%, and for calcined bauxite and then mechanically activated in Planetary Asia increased to more than 98%. TGA/DTA thermal analysis data, XRD, and SEM analyzes were used to evaluate the results. It was shown that the significant increase in reactivity of milled bauxite was mainly related to the degradation of the crystalline structure of kaolinite, and the reduction in particle size did not have much effect on this increase. By performing kinetic analyzes on leaching data, it was found that the Avrami model is most consistent with the experimental results, and this was attributed to the permeability of bauxite ores and the volumetric reaction. Finally, the activation energy for the aluminium dissolution from the bauxite by oxalic acid was calculated to be 72.4 kJ/mol.
