The Formation Of Biological Manganese Oxides And Its Adsorption And Oxidation Of Arsenic And Antimony

Manganese oxides, as a kind of highly active mineral, play an important role inthe biogeochemical element cycling of organic and inorganic, and the syntheticmechanism and environmental efficiency of manganese oxides have been of greatinterest. The oxidation of Mn2+had been demonstrated to be greatly related tomicroorganism and the rate of biological oxidation of Mn was several order higher thanchemical oxidation. In this thesis, the ability of Mn2+oxidation by manganese oxidebacteria screening from manganese mine soil was described. The characteristics ofbiological manganese oxides and mechanism of arsenic and antimony oxidized sorptionwere discussed.The main results of this study were listed as follow:(1)Pseudomonas sp. QJX-1, one strain of high manganese oxides was separatedand purified from sample of manganese mine soil, and was identified by16S rDNAsequencing. Our study shows that Pseudomonas sp. QJX-1can oxide Mn2+under1000M completely, and form dark brown tetravalent biological oxidation manganeseprecipitant. The optimum temperature of Mn oxidation is30℃, and the optimum pHrange from6.5to8.5.When the concentration of Mn2+is100M, OD600is0.020, theconversion rate of Mn2+is99.4%. The mechanism analysis shows that Pseudomonas sp.QJX-1contains CumA, a multi-copper oxidase gene that is essential for manganeseoxidation; X-ray diffraction (XRD) analysis showed that biological manganese oxides are the subject of amorphous state or short-range order. The rate of Mn oxidation byPseudomonas sp. QJX-1is more significantly enhanced in the oligotrophic conditionthan in the eutrophic conditions.(2)As3+, As5+, Sb3+and Sb5+with the final concentration of10M adsorbed bybiological manganese oxides shows that0.83mg·L-1As3+is oxidized to be As5+withoxidation rate of95.03%; But only0.022mg·L-1As5+is adsorbed on the surface ofmanganese oxide;1.377mg·L-1Sb3+is oxidized to be Sb5+with high oxidation rate of96.63%, and0.676mg·L-1Sb5+is adsorbed on the surface of manganese oxide with rateof44.49%. Full spectrum diagram of X-ray photoelectron spectroscopy (XPS) resultsshow that Mn peak appeared in642.1eV which means that Mn in manganese oxidesample is tetravalent; Sb peak appeared in532.6eV and Sb5+exists on the surface ofmanganese oxide, so Sb conversion process includes both oxidation and adsorption.However, only0.084mg·L-1As5+is adsorbed with rate of5.61%.(3)Comparing different proportion of biological iron manganese oxides removal ofAs3+, As5+, Sb3+and Sb5+, our study finds that when the initial solution of Mn2+: Fe2+is1:3, the rate of As3+removal by biological iron manganese oxides reaches71.25%;When the initial solution of Mn2+: Fe2+is1:5, Sb3+removal rate reaches37.29%; Whenthe initial solution of Mn2+: Fe2+is1:7, As5+removal rate reaches86.46%; When theinitial solution of Mn2+: Fe2+is1:9, Sb5+removal rate reaches82.09%.Our study showed that Pseudomonas sp. QJX-1and its highly reactive biologicalmanganese oxides production play a vital role in the morphology, migration andtransformation of arsenic and antimony ions in the environment, which would help tounderstand and grasp the transition and transform rule of heavy metals in the presenceof biological oxidation manganese condition, and to provide important theoretical basisfor the application of biological manganese oxides in environmental remediation.