Regulation Mechanism Of Arsenate Reducing Bacteria E.coli WC3110 On Adsorbed Arsenic Transformation

Arsenic reducing bacteria have been paid much attention due to their capability transforming As⁵⁺to As³⁺,which is more toxic and mobile.Studies on the regulation of arsenic migration and transformation by anaerobic arsenic reducing bacteria in groundwater and sediments are clearly.However,the regulatory role of aerobic arsenic reducing bacteria under the conditions of surface water,surface soil and slag,has not been clarified.Therefore,further research on the regulation mechanism and micro-interface process of arsenate is of very significance to reveal its fate under aerobic condition.In this study,aerobic arsenic reducing bacteria strain E.coli WC3110 and its arsC gene mutant were selected as tested bacteria.Four different kinds of adsorbed arsenic were used.The interactions among arsenic,bacteria,and absorbent materials were studied at the molecular level.Moreover,the effect of aerobic arsenic-reducing bacteria on the reduction and transformation in 4 different adsorbents via E.coli WC3110 was investigated using synchronous radiation.The conclusions will provide the basis for the risk assessment of the potential secondary arsenic pollution.The main results are as follows:?1?In this study,both TiO₂ and Ferrihydrite have higher adsorption capacity of As³⁺than that of As⁵⁺.However,for Al₂O₃,the amount of As⁵⁺absorbed was generally more than that of As³⁺.The amount of As⁵⁺adsorbed on Biochar was more than that of As³⁺when the concentration of As was around 1³0 mg/L.In contrast,the absorption capacity of As⁵⁺on biochar was much lower than the sorption of As³⁺when the concentration of As was over 35mg/L.In all,biochar has the strongest As adsorption capacity than other three materials and Al₂O₃ has the weakest As adsorption capacity.?2?The cell of E.coli WC3110 has adsorption capacity for arsenic.Compared with the mutant strain cell,the wild strain cell exhibit stronger arsenic adsorption capacity.Based on the SEM results,E.coli WC3110 wild live bacteria may transform the tetrahedral structure of Ferrihydrite into a sheet-like structure,which could provide a larger specific surface area and adsorption site for arsenic.Both wild and mutant strains could interact with the small particles of biochar surface,which could promote the release of arsenate.The morphology of Al₂O₃ and TiO₂ was not affected by the E.coli WC3110 cells.?3?The four adsorbed As⁵⁺were all subjected to desorption,reduction,and re-adsorption under the regulation of E.coli WC3110 wild strain.While,in the mutant strain systems,the re-adsorption of As³⁺only occurred for the TiO₂ and Ferrihydrite adsorbed arsenate.The reduction could enhance the re-adsorption of As in the system of TiO₂ and Ferrihydrite due to their strong adsorption of As³⁺.However,there is no significant influence of arsenate reduction on the re-adsorption of As in the both Al₂O₃ and biochar systems because As⁵⁺was generally adsorbed more strongly than As³⁺on Al₂O₃ and Biochar.Therefore,the reduction of arsenic and the adsorption capacity of the adsorbent co-affect the desorption and transformation of the adsorbed arsenic.In all,Ferrihydrite has a strong adsorption capacity for arsenic and lower risk of secondary pollution.For biochar,although it has a strong adsorption capacity for arsenic,the risk of potential secondary arsenic pollution was higher and should be taken consideration in the arsenic remediation.