In order to explore the commercialized applications of the low-grade bauxite in the refractory industry, a calcination integrated with acid leaching method was adopted to remove the potassium (K) and iron (Fe) from the diaspore-illite (DI) type low-grade bauxite. Following calcining the bauxite at different temperatures, the leaching parameters, including the sulfuric acid concentration, temperature, sulfuric acid to bauxite ratio, and reaction time were systematically studied. The appropriate and economical conditions for removing the impurities were found to be calcining the bauxite at 550 • C, and leaching it with a sulfuric acid solution of 1.2 mol/L, sulfuric acid/bauxite ratio of 9 mL/g at a reaction temperature of 70 • C and reaction time of 2 h, under these conditions, the removal efficiency of K and Fe from the bauxite can reach 30.32% and 47.33%, respectively. The treated bauxite was examined by XRD analysis, SEM observations, and chemical analysis. Kinetics of the removing process were calculated by two models, and the results showed that the leaching process was controlled by the mixed shrinking core model, which was affected by both the diffusion through solid layer and the interface transfer. In summary, the approach in this work presents a promising process for comprehensive utilization of the low-grade bauxite. 125 2 of 15 manufactures, and the refractory companies barely have their own bauxite mines [6]. In recent years, the ore-dressing Bayer process, intensified sintering process, and roasting pretreatment for desulphurization process was developed [7-9], following the technology advances in the industry, the Al/Si ratio requirement in Bayer process can be reduced to 4-5, and a large amount of middle-low grade bauxite is being used. Consequently, the extreme shortage of high-alumina bauxite is found in the refractory industry. In addition, there are more mineral processing researches for alumina industry than the refractory. A great number of studies in the literature on the floatation desilicication, desulfurization, and synthesizing mineral processing agents that serve the aluminum industry [10]. However, very few studies report on the purification of bauxite from the refractory point-of-view.To balance the usage of bauxite resources in the two industries and ensure their sustainable developments, it has been suggested by Zhong [11] that the beneficiation and purification should be carried out on the bauxite with low ratio of Al/Si and high content of impurity by the refractory producers.The high-temperature behavior of HAR is based on the mullite (3Al 2 O 3 ·2SiO 2 ) phase, which results from the transformation of kaolinite during the high-temperature thermal cycle [12]. In the bauxite, the main impurities that reduce the performance of refractories include Fe 2 O 3 , TiO 2 , and R 2 O (where R = K or Na). These impurities prevent the formation of the mullite and corundum phase [13,14]. It has been found that these impurities form an amorphous phase in the microstructure and that a liquid p...
