| The mobility and transformation of heavy metals in soil is affected by many factors,and the most active solid phase components in the soil include minerals and microorganisms.The two often form composites through various physical and chemical biological processes.Their effects on heavy metal adsorption,redox and other chemical reactions are different from those of single components.Therefore,the interaction between heavy metals and various solid phase components in the soil is studied.It is of great significance for the treatment of heavy metal pollution and repair.In this paper,three strains of high-tolerant microorganisms were screened from the soil contaminated by heavy metals,and the strain with the best adsorption effect was taken as the experimental strain,which was combined with iron and manganese minerals by electron microscopy and X-ray photoelectron spectroscopy?XPS?,the modern analytical techniques,combined with macroscopic adsorption experiments demonstrated the adsorption behavior of Bacillus cereus tj3,goethite and birnessite and their mineral-bacterial composites on Sb?III?and Sb?V?,and discussed the interaction between cell,heavy metals and cell-mineral composites.Finally achieved the following results:?1?Three strains with high antimony tolerance were screened and isolated from the tailings soil of Lengshui Jiang xikuangshan in Hunan Province,numbered tj1,tj2 and tj3.According to morphological observation and 16S rDNA sequence homology comparison,the result of the identification was that the strain tj1 was Ochrobactrum anthropi strain,and its accession number was MH345840.The strain tj2 is Bacillus sp.,its GenBank accession number is MH345839,and the tj3 is Bacillus cereus strain,and its GenBank accession number is MH345838.The minimum inhibitory concentration?MIC?in Sb?III?of them were 30 mM,25 mM and 25 mM,and for Sb?V?were 40 mM,35 mM and 35 mM,respectively.Among the three strains,Ochrobactrum anthropi strain tj1 and Bacillus cereus strain tj3 have the fastest growth rate.In the medium containing antimony solution,although there may have a certain inhibitory effect on the bacteria in the early stage,the bacteria will show stronger growth ability later.?2?Elucidation of the adsorption effects of three antimony tolerance bacteria on Sb?III?and Sb?V?.The pH of the solution had little effect on the adsorption of Sb?III?by three strains,but it significantly affected the adsorption of Sb?V?by the three strains,and their adsorption efficiency decreased gradually with the increase of pH.The adsorption isotherms of three anti-bacteria strains on Sb?III?and Sb?V?are combined with Langmuir adsorption isotherm equation.The best adsorption effect among the three strains was Bacillus cereus strain tj3(the maximum adsorption capacity for Sb?III?and Sb?V?was 16.6 mg·g-1 and 14.85 mg·g-1),and the adsorption effect of Ochrobactrum anthropi strain tj1 was minimal(The maximum adsorption amounts to Sb?III?and Sb?V?are 14.77 mg·g-1 and 13.29 mg·g-1).According to XPS analysis,in the process of adsorption of heavy metals by bacteria,mainly carboxyl groups,amine groups and amide groups act.?3?The adsorption behavior of antimony?Sb?on bacteria,goethite and its composites were discussed.It was found that nano-sized goethite can be tightly bound to the surface of bacterial cell wall to form goethite-bacteria complex;the adsorption of Sb?III?and Sb?V?on the surface of adsorbent accords with Langmuir equation,the maximum adsorption order For goethite>bacteria-goethite?30:70?>bacteria-goethite?70:30?>bacteria,the adsorption capacity of the complex is lower than that of a single goethite.The adsorption site;pH increased from 3 to 10,the adsorption amount of Sb?III?is basically unchanged,and it is consistent with the trend of surface charge of adsorbent;and the adsorption with Sb?V?decreases with increasing pH?It is known from the high-resolution XPS spectrum fitting of C 1s,O 1s,N 1s,The iron hydroxyl groups on the surface of goethite and the functional groups such as carboxyl and amino groups on the surface of bacteria participate in the adsorption of Sb on the goethite-Bacillus cereus composites.The results of this study have important reference significance for predicting the behavior of Sb in the multi-component interfacial micro-interface of soil.?4?The synthesis of mineral-bacterial composites of birnessites and Bacillus cereus was discussed to investigate its adsorption to antimony.Manganese oxides in soils,sediments and water systems can be strongly combined with bacterial biomass through physico-chemical processes to form bacterial-mineral complexes,which may play an important role in the mobility and fate of earthworms in the natural environment.From the macroscopic adsorption and X-ray photoelectron spectroscopy?XPS?,the water-sodium manganese ore with a mass ratio of 30:70 and 70:30 was detected.From the scanning electron microscope,we can see that the flaky birnessite is tightly bound to the bacterial surface.The adsorption of Sb?III?and Sb?V?is in accordance with the Langmuir isotherm model.The maximum adsorption order is birnessite>Bacillus cereus-birnessite composites?30:70?>Bacillus cereus-birnessite composites?70:30?>bacteria.The maximum adsorption capacity of Sb?III?and Sb?V?by birnessite(62.14 mg.g-1 and 59.2 mg.g-1)is much higher than that of the isolated bacteria(15.96 mg.g-1 and 14.3 mg.g-1)The adsorption amount of Sb?V?on birnessite,Bacillus cereus and composites material gradually decreases with increasing pH from 3 to 10,which is consistent with the change of surface charge of adsorbent.Furthermore,the antimony removed by the 30:70 and 70:30 mass ratios of cell-birnessite composites were about 50%and 16%higher,respectively,than predicted based on the behavior of two single end members under similar conditions.This non-addition phenomenon is attributed to the increased adsorption sites of Sb by the coverage of the birnessite particles.XPS confirmed the binding of Mn-O to Sb?III?and Sb?V?,and in addition,the composites also adsorbed antimony by functional group of a carboxyl group and an amino group. |
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