Isolation Of Silica Activating Bacteria And Its Activation Of Effective Silica In Electrolytic Manganese Slag

Electrolytic manganese residue?EMR?is a kind of solid waste produced during the process of electrolytic manganese.Every ton of electrolytic manganese is produced with 6-9 tons of EMR.The accumulation of EMR can easily cause serious environmental pollution,which limits the benign development of electrolytic manganese industry.At the same time,EMR contains a variety of beneficial elements.So if reasonable methods can be applied to enable the reutilization of EMR,it would have economic benefits and reduce the quantity of EMR waste which is the key to the sustainable development of electrolytic manganese industry.Silicon,as the fourth nutrient element required for plant growth,shows significant recycling value.EMR is consisted of high silicon content,but most of silicon exists in the state of SiO₂ which cannot be directly absorbed by plants.Therefore,the study on the activation of silicon in EMR is one of the effective ways to achieve the resource utilization of EMR.This paper takes the EMR?from CITIC Dameng Mining Industries Limited?as the research object,screening and isolating the bacteria from the soil around the EMR bank with leaching effect of silicon.And the bacteria with best genetic stability and best leaching effect of silicon is identified.At the same time,the optimization of bioleaching conditions and the analysis of activation mechanism provide theoretical basis for the resource utilization of silicon in EMR.The specific research contents and conclusions are as follows:?1?Breeding of silicon-activated bacteria.Nineteen bacteria with leaching effect of silicon were isolated from the soil surrounding the EMR bank by using alexandrov culture medium?silicate bacteria specific culture medium?,and 10 of them were selected for directional screening by comparing with Bacillus mucilaginosus in terms of morphology,physiological and biochemical characteristics.Four dominant strains were selected based on the ability to produce acid and extracellular polysaccharides.In addition,the optimal growth conditions for bacteria are:temperature of 30 ^oC,medium pH=7.5,shaking speed of 200 rpm,fluid volume of 100 mL,inoculum concentration of 10%.The mutagenic strain T-07 was selected through the evaluation of ore leaching.After the ultraviolet mutagenesis and nitrosoguanidine mutagenesis,the strain with the best genetic stability and the most ideal leaching effect of silicon in EMR was selected and identified as Palladium bacillus.?2?Optimum conditions for bacterial leaching effect of silicon.After the Palladium bacillus was acclimated by culture medium containing EMR,single factor experiment was conducted to explore the influence of different factors including the type of culture medium,particle size of EMR,pH value of the biosystem,culture time,culture temperature and shaking speed on the leaching effect of silicon in EMR.The results showed that in the alexandrov culture medium,if pulp density was adjusted to be 10%,the bacterial initial concentration in the medium of 10⁷ cell·mL^-1,particle size of 80 mesh,pH 7.0-7.2,temperature of 30 ^oC,shaking speed of 180r·min^-1 and leaching time of 20d,the leaching effect of silicon was best,which reached up to 123.88 mg·L^-1.?3?Activation mechanism of silicon in EMR.Through SEM analysis,it was found that the columnar structure of the particles was damaged to a certain extent after bioleaching,the surface was no longer smooth and was very fuzzy.The IR results showed that silicates were contained in the leaching solution after bacterial action.The results of XRD analysis showed that the silicate mineral components of EMR were reduced to different degrees after bioleaching,indicating that the Palladium bacillus had selective dissolution of different silicate minerals.Direct/indirect contact between bacteria and minerals showed that the effect of Palladium bacillus on silicate minerals in EMR was completed under the synergistic effect of bacteria growth and metabolites.In the study on the bioleaching effect of Palladium bacillus on different silicate minerals,the selectivity of the bioleaching effect was verified.Among them,the quartz with frame structure was difficult to be dissolved,while the muscovite and biotite with layered structure had better leaching effect of silicon.