Abstract:In view of the characteristics of low alumina, high silicon and high iron in bauxite in Yunnan, the roasting-alkali leaching pre-desiliconization process is used to obtain aluminum concentrate with high aluminum -silicon ratio. The optimal conditions are determined by investigating the effects of roasting temperature, roasting time, alkali leaching time and liquid-solid ratio on the pre-desiliconization effect. Under the optimum conditions, the aluminum-silicon ratio of low-grade bauxite is increased from 4.08 to 17.98, the silicon removal rate reaches 77.31 %, and the relative dissolution rate of alumina of pre-desiliconization concentrate is ideal to 94.56 %. Combined with Thermogravimetric Analysis-Differential Scanning Calorimetry, X-Ray Diffraction and Infrared Absorption Spectrometry, the mechanism of roasting-alkali leaching pre-desiliconization is analyzed. The results show that the improvement of the aluminum-silicon ratio of bauxite is due to the fact that the kaolin-type silicate minerals are first converted into amorphous SiO2 in roasting-alkali leaching, and then dissolved in atmospheric pressure alkali leaching.