1National Pingtung University of Science and Technology
Manganese(IV) oxides produced through microbial activity, Mn biooxides, are believed to be the most abundant and highly reactive Mn oxide phases in the environment. They mediate redox reactions with organic and inorganic compounds and sequester a variety of metals. Bacterium No.16 isolated from serpentinitic soil in Taiwan which can produce Mn biooxides in medium contained manganese carbonate. We attempted to increase and accelerate the production of Mn biooxides by No.16 and test the Cr(III) oxidation potentials of these Mn biooxides, the ultra fine structure also examined by SEM and synchrotron radiation-based FTIR. Cr(VI) was determined by DPC method, while Mn biooxides were determined by the LBB method. Mn biooxides was produced at 20th days in culture and then increase sharptly to a plateau at 24th days. The maximum production of Mn biooxides is 0.017mg/L in liquid culture of Mn oxidizing bacteria for 38days. About 5%-11% of added Cr(III)(50μM) in chromium(III) nitrate solution was oxidized to Cr(VI) within 24hrs mixing with culture filtrate of Mn oxidizing bacterium. The SEM image of Mn biooxides shows a long narrow strip with different length. The energy dispersive spectrometry analysis can be seen clearly peak of manganese. It also showed that the biogenic Mn oxides contained a small amount of Mg and Ca. The synchrotron radiation-based FTIR show the bacterial cell was closely bound with Mn biooxides. The results show the research in releasing Cr(VI) from Cr(III) contaminated sludge by application of Mn biooxides is feasible in the future.
keywords:Cr(III) oxidation potential,manganese oxidizing bacterium,manganese biooxides