Study On The Degradation Mechanism Of Bisphenol A By Fenton-like Reaction With Hydrogen Peroxide Catalyzed By A Chlorophyl Derivative

The Fenton technology,characteristic for producing strong oxidizing hydroxyl radicals（·OH）through the reaction of ferrous ions and hydrogen peroxide,has been practically applied to industrial wastewater treatment.However,the reaction needs to be carried out under a acidic pH.The continuous addition of ferrous sulfate also results in the generation of lots of iron sludge,which may cause secondary pollution and limit its development.In recent years,some Fenton-like systems with organic compounds such as iron ligands have attracted extensive attention due to their wide range of operational pH and generation of less iron sludge.But there are still some problems,such as low degradation efficiency,large biological toxicity of the ligand,complicated synthesis route,and high cost.Therefore,natural chlorophyll is used to be coordinated with ferric ion after some modification to prepare a Fenton-like catalyst in this paper.Hydrogen peroxide（H₂O₂）is employed as an oxidant.The main results and conclusions are summarized as follows:（1）The effects of SFC concentration,H₂O₂ concentration and pH of solution on the degradation efficiency of BPA were studied by optimization experiments.Under the optimal reaction conditions（molar ratio,SFC:BPA:H₂O₂=1.2:1.0:50,pH=9.0）,the degradation rate of BPA was 95%after 5 min.The reaction rate constant was about 8 times higher than that of traditional Fenton reaction under acidic condition,also higher than other Fenton-like systems reported in the literature.In addition,SFC was stable as a Fenton-like catalyst because almost no leached iron ions were detected during the reaction.The introduction of inorganic anions(Cl^-,SO₄^2-and HCO₃^-)and humic acid also showed no impact on the degradation efficiency of SFC,which had been proved to reduce the efficiency of traditional Fenton system.（2）The reactive oxygen species produced in SFC system was identified as high-valent ferroporphyrinπ-cation free radical,O=Fe^Ⅳ（Por）^+·preliminarily through free radical quenching experiment,EPR,UV-Vis and cyclohexene epoxidation experiments.Subsequently,the molecular structure of O=Fe^Ⅳ（Por）^+·and the valence state of iron were further determined by Fourier transform high resolution mass spectrometry and M?ssbauer spectroscopy.（3）The density functional theory（DFT）calculation was carried out under three spin multiplicities（doublet,quartet,sextet）with Gaussian.Six reaction intermediates and two transient states were determined in each multiplicity,which provided a theoretical basis for the analysis of the reaction of SFC and H₂O₂.The computation showed that the O-O bond of H₂O₂ cleaved homolytically when reacted with SFC,resulting in the generation of an·OH.However,the·OH tended not to be released into the solution but to stay next to SFC molecule instead.It would extract another proton of H₂O₂ and an electron of the SFC porphyrin ring to form a stable H₂O molecule and O=Fe^Ⅳ（Por）^+·through“proton-coupled electron transfer”mechanism.In addition,the reaction of SFC and H₂O₂ prefer the doublet and quartet route due to their lower energy barrier.