Preparation Of Biogenic Manganese Oxides By Autotrophic Manganese Oxidizing Bacteria And Removal Efficiency Of Organic Pharmaceuticals

The pharmaceuticals have raised significant concerns in recently years for their persistent input and potential threat to ecological environment and human health. Although most sewage treatment plants can remove some pharmaceuticals, there are still many pharmaceuticals removed incompletely and thus discharged to the environment. In this study, biogenic manganese oxides are exacellular metabolismis of autotrophic manganese oxidizing bacterium, with the characteristics of high specific surface area, high redox potential and surface activity. They not only can adsorb heavy metals, but also can degrade organic compounds in the aquatic envrionment. Thus, to investigate utilizing manganese oxidizing bacteria to produce biogenic manganese oxides to remove pharmaceuticals in the aquatic environment is a new cost-effective technology for water treated.In this experiment,3 strains of autotrophic manganese oxide bacteria has been isolated for long-term domestication of enrichment in the running stability of the aeration biological filter, and has been identified by 16 S rDNA sequencing, then, chose one strains(M2) was used to synthesis and XRD analysis of biogenic manganese oxide. The removal efficiencies of diclofenac and carbamazepine were researched by biogenic manganese oxides.The key results and conclusions were as follows:3 strains of autotrophic manganese oxide bacteria(M1?M2 ? M4) has been isolated for long-term domestication of enrichment in the running stability of the aeration biological filter. According to its morphology, physiochemical characteristics and 16 S rDNA sequence analysis, M1 strains was identified as Streptomyces, and M2 strains was identified as Paracoccus marcusii strain, and M4 strains was identified as Streptomyces lienomycini strain. According to the relevant literatures at home and abroad, there has been little research on the study of autotrophic manganese oxide bacteria, thus, the 3 strains were proposed as the new species.XRD was used to characterize the biogenic manganese oxides which M2 synthesised. It was found that biogenic manganese oxides were disordered state, weak crystalline structures, and the main morphology liked MnO2, Mn3O4, Mn2O3 and MnOOH.Experiments on elimination of diclofenac indicated that diclofenac removal was enhanced at low pH. At lower pH, higher H+ concentrations in the solution would increase the driving force of the reaction. Besides, according to the Nernst Equation, a decrease in pH would cause an increase in reduction potential of MnO2. The change of surface charge also would facilitate the electron transfer reaction, then, more active sites on MnO2 surface could be created for promoting the oxidative degradation of diclofenac in acidic solution.So, when the lower the pH, the better the removal rate of diclofenac. After 5 minutes of reaction, the removal rate was 100% at pH 2.0; After 90 minutes of reaction, the removal rate was 100% at pH 2.8; After 120 minutes of reaction, the removal rate was 94.3% and 83.4% at pH 3.8 and 5.0, respectively.Experiments on oxidative degradation of carbamazepine indicated that there was no obvious removal efficiency at different pH.