Degradation Of Typical Endocrine Disrupting Compounds By Biogenetic Mn Oxides: Influencing Factors,Degradation Products And Possible Degradation Pathways

Endocrine disrupting compounds(EDCs)are similar in structure to natural hormones in humans and wild animals,so they can mimic the chemical properties of natural hormones in the endocrine system,adversely affecting humans and wild animals.Among them,bisphenol A(BPA)and 17?-ethinylestradiol(EE2)are considered to be major contributors to the activity of EDCs in sewage.Considering the increasing demand for reuse of wastewater for agriculture and drinking water,further improvement to remove EDCs is required and necessary.The biogenetic Mn oxides produced by bacteria is nano-material.Compared with chemically synthesized Mn oxides,biogenetic Mn oxides have many advantages,such as high redox potential,large specific surface area,high catalytic activity,excellent adsorption performance,mild synthesis conditions and green friendliness.Therefore,there are considerable potential applications for biogenetic Mn oxides(Bio-MnOx)in the field of water pollution treatment.In this experiment,Bio-MnOx was prepared by Bacillus sp.WH4 and characterized by XRD,SEM,FE-TEM-SAED-EDS/Mapping and XPS.Mn oxides produced by Bacillus sp.WH4 are deposited on the surface of cells or scattered around.These Mn oxides are amorphous nano-materials.The oxidized Mn has two valence states of Mn(III)and Mn(IV),each accounting for 23.56% and 76.44%,which indicates that Mn(II)is first oxidized to Mn(III)intermediate and then oxidized to Mn(IV).Two typical EDCs-BPA and EE2,were degraded by Bio-MnOx.The influence of pH,organic matter concentration and Bio-MnOx dosage on degradation experiments were studied.The results showed that when pH was 5.0,BPA was 1.0 mg/L,and Bio-MnOx was 40 mg/L,the BPA removal efficiency could reach 88.1% and ~100% at 15 min and 45 min,respectively.The BPA removal efficiency at different pH was in following order: pH 5.0>pH 6.0>pH 8.0>pH 7.0.Moreover,the BPA removal efficiency decreased with the increase of BPA concentration and the dosage of Bio-MnOx.For EE2 removal by Bio-MnOx,the removal efficiency at different pH were ranked as follows: pH 5 > pH 6 > pH7 > pH 8.The removal efficiency of EE2 decreased with the increase of pH,decreased with the increase of EE2 concentration,and enhenced with the add of biogenetic Mn oxide dosage.When the pH was 5.0,the concentration of EE2 was 1.0 mg/L,and the Bio-MnOx dosage was 8 mg/L,the EE2 removal efficiency was 93.9% at 2 h.Solid phase extraction-(derivatization)-GC-MS was used to determine the BPA degradation by Bio-MnOx.Three kinds of degradation products were determined without derivatization after solid phase extraction,and 13 kinds of degradation products were detected with derivatization.According to GC-MS results and related references,the degradation of BPA by biogenetic Mn oxides was mainly achieved by coupling,oxidative condensation,elimination,cracking.Seven degradation products were determined by solid phase extraction-derivatization-GC-MS.According to the measured degradation products,it can be speculated that EE2 degradation by Bio-MnOx was mainly through substitution and cleavage reaction.