| Arsenic belongs to metalloid and its physical and chemical properties are similar to other heavy metals.Therefore,arsenic pollution is currently included in the research of heavy metal pollution.Microbial adsorption method has become the focus of current research,due to its wide application scope,low operating cost,large adsorption capacity,and good adsorption effect for heavy metals combined arsenic.Extracellular polymers play an important role in the treatment of heavy metal pollution.However,there are few studies on extracellular polymers.The mechanism of arsenic removal from extracellular polymers is not yet clear.In this study,three strains of arsenic-tolerant bacteria were obtained from the soil of arsenic-contaminated tailings sites by screening bacteria,and then the distribution of arsenic in three bacterial sub-cells was compared to obtain the dominant bacteria whose extracellular polymer accounted for a large proportion of the total removal rate of arsenic.XPS,FTIR were used to study the mechanism of arsenic removal by the bacteria and its extracellular polymers.The main conclusions:(1)Three strains of arsenic-tolerant bacteria were successfully selected from arsenic-contaminated tailings sites in a metal mine in Leng shuijiang,Hunan Province.16S rDNA analysis confirmed that bacteria 1,bacteria 2 and bacteria 3 belonged to Bacillus Cohn,Bacillusamyloliquefaciens,pseudomonas aeruginosa,respectively.And the anastomosis of sequencing results was 100%.(2)The three arsenic-tolerant bacteria could all grow normally under high-arsenic condition,and had good removal effect on low-level arsenic,with extracellular removal as the main part.When the concentration of arsenic was 500-50000?g/L,the three strains showed strong resistance to arsenic.And bacteria 3 namely Pseudomonas aeruginosa was more tolerant to arsenic than the other two strains.When the concentration of arsenic was 5mg/L,the extracellular proportion of Pseudomonas aeruginosa was the highest,reaching 66.57%of the total removal rate.(3)EDTA was the optimal method to extract extracellular polymer of pseudomonas aeruginosa.Results of 4 kinds of extraction methods showed that the overall extraction effect was:EDTA>formaldehyde-NaOH>centrifugation>low temperature heating method.The amount of polysaccharide in extracellular polymer extracted by EDTA was higher than protein.The concentration of extracellular polymer was 1.659?g/L,in which the rate of C/O and N/O in the extracellular polymer were 1.790 and 0.316,respectively.(4)XPS and FTIR were used to analyzed adsorption mechanism,indicating that the main functional groups involved in the removal of arsenic by Pseudomonas aeruginosa were-OH,C=O,and the removal of arsenic by Pseudomonas aeruginosa was mainly related to carboxylic acid and alcohol substances.The functional groups involved in the removal of arsenic by extracellular polymers of Pseudomonas aeruginosa were mainly-OH-,C=C,-CH2,and-COO-,and the removal of arsenic by extracellular polymers was mainly related to carbohydrates,unsaturated hydrocarbons,Carboxylate.The strongest energy peak that Pseudomonas aeruginosa and its extracellular polymers combined with Arsenic was 41.29 eV.And arsenic was removed by them in the form of As(+3). |
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