Abstract
The current study deals with preliminary chemical activation, which allows transforming the phase composition before gravitational concentration and effective removal of silicon during subsequent alkaline treatment, in order to obtain a raw material suitable for the production of alumina by the Bayer method. Electron-microscopic analysis of the original bauxite showed that the coarse-crystalline fraction was tightly pressed by the fine one. Silicon modulus of the averaged bauxite sample is 3.65. After chemical activation of bauxite in a sodium bicarbonate solution, the fine fraction got separated from the coarse fraction and the phase composition changed i.e. the calcium silicate phase disappeared and the calcite phase was formed. Preliminary chemical activation at temperatures of 90 and 120 оС for 20 min resulted in the increase of the bauxite beneficiation degree by 12.1 and 15.2%. In order to obtain a quality bauxite concentrate with a silica modulus of more than 7, the coarse-grained bauxite fraction separated after gravity concentration should be subjected to chemical beneficiation in an alkaline solution at a second stage.