The Effects Of High Efficient Silicon Releasing Bactera On Silicon Remove From Bauxite And Its Mechanisms

In China,most of bauxite is the diaspore,with high aluminum and silicon,accounting for about 98%.It is of significance for the Bayer process to increase A/S by bio-removal silicon.In this article,we chose three different strains stored in our laboratory and optimized the c?Lture conditions of these three strains.The relationship between element release and growth of the strains in c?Lture solution and on mineral surface were determined.To provide technical support for bio-removal silicon from.Three different strains,Ensifer adhaerens M78,Arthrobacter pascens H19 and Burkholderia anthina G27 were chosen as the test strains.In the seven day-leaching test,the concentration of Si released by strain M78,H19,G27 were 56.18 mg/L,52.43 mg/L,53.58 mg/L,respectively.The three strains increased Si release by 185%,166%and 172%compared to the control(19.7mg/L).But the release of Al from the mineral by the three strains were 0.31 mg/L,2 mg/L and 2.15 mg/L,respectively,which is much less than that contained in bauxite.Therefore,these three strains have efficient ability to remove Si from bauxite.The desiliconization experiments of the three strains were conducted in the SSKM medium,nitrogen-free SSKM medium and BH medium.The experiments showed the best disilication from bauxite by the three strains in SSKM medium.We optimized the c?Lture conditions and proportion of carbon and nitrogen in medium by Single Factor Test and Response Surface Method.The res?Lts showed that the biomass(OD600)of strain G27,M78,H19 in the optimized c?Lture after one day were 0.418,1.02 and 1.839 significantly increasing than that 0.265,0.774 and 1.494 before optimization.The res?Lts also showed that the concentration of Si dissolved by strain H19 and G27 reached 55 mg/L and 54 mg/L after optimization which were significantly higher than that before optimization.There was no remarkable change of Si released by M78 and Al released by all the three strains.The leaching test showed that the desiliconization by mixed stains H19+M78 and G27+M78 were much better than strain H19 or G27.The efficiency of desiliconization by mixed strains H19+G27 was less than strain H19 or G27.We found that organic acids and exopolysaccharides contributed to the elements dissolution in the early period of the 15 days of incubation by detecting th?e dynamic changes of bacterial growth,element released and bacterial metabolites in the c?Lture solution and on mineral surface.In the middle and late period of incubation,element dissolution was dependent on the bacterial adsorption on the mineral surface.Al concentration was decreased in c?Lture solution in middle and late period of strain M78 because of the reprecipitation on mineral surface which hindered the bacteria in contact with the mineral.So the Si leaching rate caused by strain M78 was lower than the other two strains.Exopolysaccharides and organic acids had a effect on the desiliconization.Effects of exopolysaccharides mixed with organic acids were greater than that of a single factor.Sterile c?Lture media also had an effect on desiliconization,but bacteria had higher effect on desiliconization.