| Manganese dioxide is an important natural oxidant, which plays the role of environmental remediation and purification. Because it can degrade organic pollutants, and hence reduce toxicity of the pollutants. While this process is a solid-liquid-phase catalytic reaction, as the reaction proceeding, manganese dioxide will be reduced gradually and Mn2+concentration will be increased, thus the removal efficiency will be cut down significantly. Therefore, the aim of this paper is to screen an efficient oxidizing-bacteria, which can oxidize Mn(Ⅱ) to form the biogenic Mn oxides, and restore the oxidative degradation ability of manganese dioxide in the lasting system.One Mn2+oxidizing bacteria was isolated from the mature manganese sand collected from one waterworks. According to it’s morphology, physiochemical characteristics and16S rDNA sequence analysis, the strains was identified as Aminobacter sp. and named as H1. According to the relevant literatures, this strain was proposed as a new specie which can oxide Mn2+efficiently. The optimal temperature and pH for Mn2+oxidation by the strain H1in the shaking flasks were35℃and7.0, respectively. Under the optimum conditions, Mn2+could be removed completely within5days by this train when Mn2+concentrations were ranged from0to10mmol/L, and the maximum oxidiation rate was more than60%. When1g/L of ammonium ferric citrate was added in the medium, oxidative capacity of the strain was strengthened. Furthermore, this strain had tolerance to high concentration of MnCl2(50mmol/L) and oxytetracycline (60μmmol/LOTC).At different growth stages, the strain had different oxidation ability. In the late exponential phase and stationary phase, oxidation activity was the strongest, but it was significantly decreased in the decline phase, which indicated that manganese oxidation activity of the strain had a strong relationship with bacterial activity. During the process of bio-oxidation, Mn(Ⅲ) was detected. The strain could oxide Mn2+by producing activity factor and alkaline metabolites to increse the pH value in the medium. The presence of Mn2+not only can induce the production of activity factor, but also can enhance the amount of activity factor. Cell lysates, microbial cells, culture medium and the supernatant all have the oxidation activity, and the oxidation capacity was followed the order:cell lysates <supernatant<bacterial<culture medium.SEM-EDX, XRD, and XPS were used to characterize the biogenic Mn oxides. It was found that lots of biogenic Mn oxides coved on the bacterial surface, which were disordered state and weak crystalline nanostructures, and the morphology liked MnCO3, MnOOH, Mn3O4and MnO2.Batch experiments were conducted to study the degradation of OTC by biogenic Mn oxides and δ-MnO2. It was shown that OTC could be degraded completely both by the two systems, and the OTC degradation rates were increased with the increasing of initial concentration of Mn oxides, while decreased as pH increased from4.0to8.0. While the degradation efficiency of biogenic Mn oxides was slightly higher than that of δ-MnO2.Under the conditions that the concentration of substrate was50μmol/L, the initial concentration of δ-MnO2was500μmol/L, pH value was7.0, and the inoculation amount of bacteria was20%, the coexist circulation system of manganese dioxide and manganese oxidizing bacteria was constructed successfully, in which the rest OTC can be completely removed and the generation Mn2+was reoxidized.This study could provide useful information to better understanding the fundamental knowledge relevant to the interaction of antibiotics and manganese oxides in natural environment, but also provide new ideas to improve the technology of controlling environmental pollutants by the manganese oxide. |
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