Preparation Of Biogenic Manganese Oxides And Oxidative Degradation Of Bisphenol A And17α-ethynylestradiol

Endocrine disruptors with remarkable estrogen effects are detected at low levels inwastewaters and surface waters throughout the world; even trace amounts will adverselyaffect the reproductive functions of human beings and wildlife via interaction with theendocrine system. However, regular wastewater treatment process cannot reach a highremoval rate of endocrine disruptors at mg/L levels; the absorption efficiency of activesludge is much lower when the wastewater samples are collected in site containingcomplex contaminants instead of prepared in laboratory containing only onecontaminant; advanced oxidation process with an outstanding performance indegradation of endocrine disruptors have a high energy consumption and may alsocause secondary pollution. Biogenic Manganese Oxide (BioMnOx) is exacellularmetabolismis of manganese oxidizing bacterium, prepared with high concentration Mn+present. BioMnOx with the characteristics of high specific area, oxidizability andsurface activity, can degrade organic contaminant rapidly and efficiently. Besides, Mnoxides can be reprecipated by microorganism after interaction with contaminants,decreasing the possibility of secondary pollution. In this study, BioMnOx prepared byBacillus sp.WH4were tested for the removal of Bisphenol A (BPA) and17α-Ethynylestradiol (EE2), and factors affecting the reaction, such as pH, initialconcentration of BioMnOx and contaminants, were also investigated.Experiments on oxidative degradation of BPA indicated that acidic or basicconditions facilitated BPA removal, whereas neutral conditions disfavored the reaction.After2hours of reaction, BPA removal rates were100%,92.9%,61.6%, and80.8%atpH5.0,6.0,7.0, and8.0, respectively. The oxidation of BPA by MnO2is initiallytriggered by surface reactions on the oxide, where subsequently loses electrons to theoxide, and the accessible sites on the oxide and its oxidation potential can greatlyimpact the reaction rate. After2hours of reaction, BPA removal rates were100%and51.45%for systems added with0.5mg/L and4.0mg/L BPA, respectively. On the otherhand, after2hours reaction, BPA removal rates reached49.5%and100%for systemsadded with10mg/L and40mg/L BioMnOx, respectively.Experiments on oxidative degradation of EE2indicated that EE2removal wasenhanced at low pH. Among the4control groups, the removal rate was94.3%at pH5.0while below15%at pH8.0. Oxidative degradation of EE2by BioMnOx is a surface-dependent reaction that can be promoted by increasing the number of surfacereactive sites. After2hours of reaction, EE2removal rates were100%and60.3%forsystems added with0.5mg/L and4.0mg/L EE2, respectively. On the other hand, after2hours reaction, EE2removal rates reached81.2%and100%for systems added with4mg/L and16mg/L BioMnOx, respectively.