Mineralization Of Manganese Carbonate Minerals Induced By A Strain Of Bacillus Cereus And Its Adsorption On Cadmium

Under the high cadmium background value of karst carbonate rocks,The life activities of soil microorganisms in the ecological environment are closely related to environmental metal ions.The life metabolism activities of microorganisms and the function of inducing mineralization have a certain influence on the movement and transformation of heavy metal ions in the environment.Explore the mechanism of manganese mineralization bacteria inducing mineralization to form manganese carbonate,Adsorption of heavy metal cadmium(Cd)by biogenic manganese carbonate minerals,To understand the biological functions of environmental microorganisms in karst areas and the ways of Biogenic adsorbent materials have important significance and value to the mechanism and application of heavy metals.In this paper,a dominant bacterium(Bacillus cereus)CH-1 was isolated and screened from the cultivated land in the karst area of Luodian County,Guizhou Province.The physiological role of this strain in inducing the formation of manganese carbonate minerals and the adsorption mechanism of heavy metal cadmium(Cd)by biogenic manganese carbonate minerals were studied.The main results are as follows:1.Six strains of manganese mineralization bacteria were screened from farmland soil in Dahao Village,Luodian County,Guizhou Province,and their manganese mineralization ability was identified by the LBB method.It was determined that strain 6 had stronger mineralization ability than other strains,and was named CH-1.2.The growth conditions and growth curve of the CH-1 strain are optimized.The number of bacteria is the highest when the initial p H is 7.0.The manganese mineralizing bacteria CH-1 is in the logarithmic growth phase at 2-27 h,in the stable phase at 27-44 h,and then enters the decline phase.The CH-1 colony was round in shape,wrinkled on the surface,slightly raised,and milky white.Gram-stained bacteria were positive.They were able to move,reduce nitrates,and could not hydrolyze starch.Both Fupp and methyl red tests were positive.According to the 16 S r RNA molecular identification,this strain has the highest homology with Bacillus cereus,and the similarity is 100%,so it can be preliminary identified as Bacillus cereus.3.Bacillus cereus CH-1 was used to induce the synthesis of manganese carbonate minerals.The results showed that mineral precipitation appeared on the 3rd day of culture,and the minerals appeared as spines after the 20 th day of culture;the content of polysaccharides in the liquid phase product increased over time.And the p H increased from the initial 7.0 to above 9.0.4.The biogenic manganese carbonate mineral adsorbs the heavy metal cadmium(Cd).The results show that the adsorption equilibrium is reached after 36 hours of adsorption.The adsorption effect is the best in the system when the p H is 7.0 and the adsorbent dosage is 1.2 g/L,which is in line with the pseudo-secondary level.The adsorption reaction kinetic model,the adsorption capacity is 16.49 mg/g.The analysis of adsorption thermodynamics shows that the adsorption process of biogenic manganese carbonate minerals for cadmium(Cd)conforms to the Langmuir isotherm adsorption model,with a maximum adsorption capacity of 60.168 mg/g,and the adsorption type of biogenic manganese carbonate minerals is determined to be single-layer adsorption.5.Comparing the changes of biogenic manganese carbonate minerals before and after adsorption,the results show that the surface of biogenic manganese carbonate minerals is rich in many adsorption functional groups.Among them,the functional group that adsorbs cadmium is C=O,and the infrared absorption peak changes slightly before and after adsorption.The above experimental results show that the manganese mineralization bacteria CH-1 is the dominant bacteria for manganese mineralization.The manganese carbonate mineral and the induced manganese carbonate mineral have a good chelating and holding effect on the heavy metal cadmium(Cd),It has good repair value for environmental heavy metal pollution,and provides development ideas and theoretical scientific basis for the development of new adsorbent materials.