Degradation Of BPA Via Activation Of Persulfate By MIL-88B Under Visible Light

As a typical endocrine disruption substance?EDS?,Bisphenol A?BPA,2,2-bis?4-hydroxyphenyl?propane?exhibits neuro-,immuno-,developmental,and reproductive toxicities.Because of widespread usage,BPA is frequently detected in the aquatic environment.Photocatalysis system coupled with persulfate could accelerate the degradation of contaminants by forming SO₄^-·under visible light and scavenging conduction band electrons,which was regarded as a promising strategy to effectively remove BPA from aquatic environments.In this study,we synthesized a typical iron-based metal-organic framework,MIL-88B?Fe?,and constructed a MIL-88B?Fe?/persulfate/visible light?MIL-88B/PS/Vis?system for photocatalytic degradation of bisphenol A?BPA?in aqueous solution.The characterization of the prepared MIL-88B,environmental factors,kinetics,degradation mechanism and pathways,photocatalytic degradation rate of BPA in different kinds of actual water body and risk assessment in the BPA/MIL-88B/PS/Vis system were explored.Conclusions are as follows:The as-prepared MIL-88B,whose bandage was approximately 2.39e V,was needle-like with a length of approximately 1.1?m and an average width of 0.26?m,which implied an efficient response to visible light.BPA?10 mg/L?could be removed completely within 25 min with 0.6 g/L MIL-88B and 2m M PS under visible light,while the removal rates with individual MIL-88B/Vis or MIL-88B/PS was only 26.0%and 34.1%,respectively.In addition,the BPA degradation rate in the MIL-88B/PS/Vis system(0.107 min^-1)was 4.7 times higher than that in the MIL-88B/PS system(0.023 min^-1)and 8.9 times higher than that in the MIL-88B/Vis system(0.012 min^-1),respectively.The removal efficiency in tap water,river water,and dye wastewater have been significantly reduced,the removal rate and apparent rate constants of BPA degradation in those water bodies mentioned above within 30 min were 100.0%,52.8%,37.6%and 0.090?0.054?0.011 min^-1,respectively.The degradation of BPA by MIL-88B/PS/Vis has a wide range of p H applicability and the removal rate of BPA was oxygen-dependent.Most inorganic anions(HCO₃^-,SO₄^2-,H₂PO₄^-,and NO₃^-)have an inhibitory effect on the degradation while the BPA degradation process in M88/PS/Vis system could be facilitated by Cl^-.There were synergistic effects in the M88/PS/Vis system in which O₂^·-and SO₄^·-played a dominant role.The coexistence of non-free radical and free radical mechanism is the reason for the high degradation performance of the system.During the degradation process,MIL-88B would generates photogenic electron-holes pairs in the visible light,the photoinduced electrons in the CB could be trapped by PS to form SO₄^-·.Fe^?GUS?iron species in MIL-88B?worked as a heterogeneous catalytic active sites for PS activation to generate S₂O₈^-·,the Fe^?GUS could be reduced to Fe^?GUS which could activate PS to form SO₄^-·.Besides,since the CB potential of MIL-88B was more negative than the redox potential ofO₂/?O₂^-?-0.33V?,indicating that O₂^-·could be produced by photogenerated electrons.Then,part of the O₂^-·species might further form OH·and HO₂^-·radicals.Finally,generated radicals could combine with photoholes to directly oxidize BPA to some extent and completely mineralize it to CO₂and H₂O.There three ways to elucidate the BPA degradation pathways in the M88/PS/Vis system:desaturation and unsaturation progress induced by photogenerated h⁺;combined oxidation by OH·and SO₄^-·to generate compound which had a higher molecular weight than BPA;O₂^-·induced hydroxylation,in this way,a series of multihydroxylations occurred when the aromatic ring was attacked by water molecules via the electrophilic effect.Although most intermediates?phenol,p-benzoquinon,p-isopropenyl phenol?were one or more level less toxic than BPA,there were some intermediates?dimethymethan Phenol,2,4-bis?1,1-dimethyl ethyl??with higher biological toxicity than BPA and increased the toxicity of solution in the first 10min,the toxicity hazard in general could be effectively avoided by prolonging the duration of light exposure and reached completely mineralization within 75min.This research provides a profound understanding of the potential application of PS activation by photocatalyst for both BPA removal and toxicity shift under visible light.