The Adsorption Of Pb(Ⅱ)/Zn(Ⅱ) And The Oxidation Of As(Ⅲ)/Cr(Ⅲ) Of Biogenic Manganese Oxide

Manganese (III, IV) oxide minerals play a key role in the biogeochemical cycles of metals and organic carbon, significantly influence the transport and the fate of contaminants and nutrients in the environment via sorptive, catalytic, and oxidative processes. The manganese oxides formed by microorganisms have been believed to be the most highly reactive phases in the environment.In this experiment, a strain of manganese-oxidizing bacterium Pseudomonas putida sp. MnB1was selected. The impact of Mn(II) concentration and time on biogenic Mn oxide formation was investigated. The morphologies and characteristics of the biogenic manganese oxides and chemically-synthetized vernadite were determined using X-ray diffraction, N2specific surface area, electron microscopy, X-ray photoelectron spectroscopy and so on. The adsorption and oxidation characteristics of the biogenic Mn oxide and chemically-synthetized vernadite were compared. The main results were listed as following:1.0.5mmol-L-1of Mn(II)had no harmful impact on the growth of the bacteria. The growing period of the bacteria was about:adaptation period (0-4h), logarithmic period (4-9.5h), stabilization period appeared after9.5h. The decline period didn’t appear within the detection time (24h).2. The optimum conditions of biogenic Mn oxide formation:The manganese-oxidizing bacterium was cultured in the medium with0.5mmol L-1Mn(II) at25℃,200r min-1for7days.3. The biogenic Mn oxide was vernadite, containing bacterial substances. NaClO treatment did not have much impact on the x-ray diffraction (XRD) patterns of the product. X-ray photoelectron spectroscopy (XPS) analysis results indicated that the biogenic Mn oxide containied more Mn(III)and Mn(II), at the proportion of37.16%and9.55%, the average manganese oxidation state was3.44; whereas the chemically-synthetized vernadite contained more Mn(IV), at the proportion of89.34%, the average manganese oxidation state was3.88. 4. The adsorption isotherms of biogenic Mn oxide and synthetic Mn oxide were well fitted with Langmuir model. The biogenic Mn oxide adsorbed832.24mmol Pb(II) and268.51mmol Zn(II) kg-1, while the chemically-synthetized vernadite adsorbed3693.09mmol Pb(II) and887.75mmol Zn(II) kg-1. It’s probably due to the extracelluar polymer wrapped in the surface of biogenic Mn oxide which influenced the surface properties.5. In the process of As(III) oxidation, the oxidation rate of biogenic Mn oxide was greatly faster than that of vernadite. The oxidation ratio was80%of biogenic Mn oxide, which was only12%for vernadite. However, in the process of Cr(III) oxidation, the oxidation rate of vernadite was faster than that of biogenic Mn oxide. The oxidation ratio was70%for vernadite, whereas which was60%for biogenic Mn oxide, it’s may be related to Mn(III) in the biogenic Mn oxide.