Modification of the phase composition of low-grade gibbsite-kaolinite bauxites

Abstract

The known methods of processing low-quality bauxite have a number of disadvantages that make it difficult or impossible to use them in the conditions of production of JSC "Aluminum of Kazakhstan", therefore, it is necessary to effectively develop a technology for preliminary enrichment. Enrichment of low-quality bauxites is possible by separating the clayey - high-siliceous and coarse-crystalline fractions. Electron-microscopic analysis of the original bauxite showed that the coarse-crystalline fraction is tightly pressed by the fine one. The total silicon modulus of the sample is 2.49. The silicon modulus of the fine fraction is 2.19, and that of the coarse fraction is 3.89. When enriching bauxite, as a result of the separation of fines, it is possible to increase the silicon modulus. After the chemical activation of bauxite in a sodium bicarbonate solution, the finely dispersed fraction is effectively separated from the coarse one and the phase composition changes - the calcium silicate phase disappears and the calcite phase is formed. With an increase in the activation temperature, the content of kaolinite and siderite decreases, and the content of quartz and hematite increases. Studies have shown that at temperatures of chemical activation of 120 ° C, duration of more than 120 minutes and 200 ° C, duration of more than 40 minutes, a dawsonite phase is formed in bauxite, which densifies the mineral structure. When determining the optimal regime for carrying out chemical activation, it is necessary to take into account the negative possibility of dawsonite formation.