The Interaction Among Extracellular Polymeric Substances From Bacteria,Goethite And Birnessite And Its Effects On Oxidative Reactivity Of Birnessite

Birnessite and goethite are widespread in soils and sediments.Bacteria produce a lot of Extracellular Polymeric Substances(EPS)in their growth and metabolism.So the interaction between these three components are inevitable.Although numerous studies have reported the interaction between manganese oxide and a single metal oxide,or the interaction between natural organic matter with a single metal oxide,but there are no reports on the interaction of EPS with goethite and birnessite.Based on this,in this study,EPS,goethite and birnessite were used as the research object,the interaction mechanism between these three components were investigated by using equilibrium experiment,attenuated total reflectance-fourier transform infrared spectroscopy(ATR-FTIR),sedimentation experiment,isothermal titration microcalorimetry(ITC)and high performance liquid chromatography(HPLC).In addition,triclosan(a widely used antimicrobial agent)was used to detect the oxidation reactivity of birnessite in ternary systems with goethite and EPS in pH5.The major results were summarized as follows:1.The effect of EPS on the oxidative reactivity of birnessite was studied by combining birnessite with goethite.The oxidative reactivity of birnessite was inhibited by positively charged goethite,mainly through the strong heteroaggregation with the negatively charged birnessite and EPS can improve the oxidative reactivity of birnessite in binary complex.2.The thermal effect between EPS,goethite and birnessite is significantly higher than that between EPS and goethite.The adsorption behavior of EPS on the surface of goethite and goethite-birnessite complex are both exothermic reaction.3.In the ternary system of birnessite、goethite and EPS,compared with unadded EPS,after adding 0.2mg-C/L or 0.4 mg-C/L EPS,they had the same sedimentation rate.It’s because in this concentraction of EPS,it improved the goethite’s homoaggregation,but inhibited the heteroaggregation between birnessite and goethite.