Application Of Silicate Bacteria In Bauxite Biodesilication And Bioleaching Mechanism

Bauxite is the important raw material of alumina. Only bauxite (Al/Si≥8) would be to produce alumina in the Bayer process. In China most of bauxite are the diaspore type with high aluminum and silicon, therefore, it is important to study the silicon removal from bauxite. This paper takes Henan bauxite as the research object, using microbial technology to carry out research to improve the ratio of silicon and aluminum, focuses on the research of bauxite desilication is suitable for microbial breeding and the mechanism of silicate bacteria in bauxite bioleaching.Firstly, the6strains of silicate bacteria were isolated by ordinary screening, the best culture condition optimization out strains as initial pH7.0, temperature30℃, the shaking speed200rpm, inoculation amount10%;4strains of bacteria were screened by means of directional selection according to the ability to produce acid and extracellular polymers; by UV mutation or chemical mutagenesis, screening and subculture testing, stable silicon-leaching strain JG-02-U02was discovered.By single factor test and orthogonal test, silicate bacteria leaching optimum conditions were initial pH7.0, temperature30C, the shaking speed200rpm, inoculation amount10%, slurry concentration of5%, ore particle size is about0.056mm. Under this condition, Al/Si of bauxite can be increased from5.17to11.51by the mutant strain the JG-02-U02, while it can be improved to9.77by the strain JY-03.The results showed that the mutation can improve the ability of removing silicon strain.Desilication efficiency were studied on the mixed strains (strain JY-03, JG-02and B.M mixture) and the continuous leaching process. Al/Si of bauxite can be increased to13.21through15days of continuous leaching, and up to57.4%silicon was moved out. The depth desilication of bauxite was processed with the mixed strain and the continuous leaching process.Studies on the metabolites of bacteria show that the silicates were extractived by organic acids, amino acids, extracellular polymeric substances produced by silicate bacteria. The test results of direct/indirect contact mode showed that desilication depends on the metabolites of silicate bacteria and bacterial growth on the mineral surface. At the same time, crystal structures of silicate minerals have important influences on the bioleaching, the layered structure of minerals would be more easily bacterial erosion and leaching than the frame structure of the minerals.