Efficient Heterogeneous Activation Of Peroxymonosulfate By Modified Catalysts For Degradation Of Tetrabromobisphenol-A

As one of the most widely used brominated flame retardants currently,tetrabromobisphenol-A（TBBPA）is also a kind of potentially persistent,bioaccumulative and toxic substance.The advanced oxidation processes based on sulfate radical（SO₄·^-）have attracted widespread attention as an effective technology for treating refractory pollutants,among which transition metal heterogeneous catalysis of peroxymonosulfate（PMS）is of great advantage.Magnetic spinel metal oxide can efficiently activate PMS,reduce the leaching of heavy metal ions,and easily be separated from treated water.In the present work,considering the large leaching and high toxicity of widely used cobalt-based catalysts,different doping and loading methods were used to modify copper ferrite（CuFe₂O₄）,thus improving its catalysis of PMS for TBBPA degradation in water.CuFe₂O₄ doped with Ce,Sn,and Sb were prepared by sol-gel combustion method,and for the first time applied as heterogeneous catalysts to activate PMS for TBBPA degradation in aqueous solution.Morphology,elementary composition and crystal structure of the obtained catalysts were characterized by means of scanning electron microscopy,X-ray powder diffraction（XRD）and specific surface area measurement.Especially,Sb-doped CuFe₂O₄（Sb-CuFe₂O₄）exhibited separated clusters of particles with voids,the weakest diffraction intensity in XRD pattern,the lowest specific surface area and broad pore size distribution.Sb-CuFe₂O₄ also performed best in the experiment of activating PMS for TBBPA degradation,and was loaded onto graphene oxide（GO）by impregnation,hydrothermal synthesis,coprecipitation and self-assembly methods respectively.As a result,the supported catalyst prepared by coprecipitation exhibited the best catalytic performance,and was greatly improved compared with the unsupported.In PMS/Sb-CuFe₂O₄ system,the degradation of TBBPA was comprehensively investigated under various factors.It was found that 90.1% of 15 mg/L TBBPA was removed at pH 8.3 in the presence of 0.2 m M PMS and 0.075 g/L Sb-CuFe₂O₄.The reaction efficiency was significantly influenced by catalyst and PMS dosage,as well as initial pH.The presence of Cl^-,NO₃^-or SO₄^2-slightly inhibited the degradation,while the addition of CO₃^2-,H₂PO₄^-,or natural organic matters significantly inhibited the oxidation process.Sb-CuFe₂O₄ also exhibited favorable reusability and stability in multiple runs and good performance in actual wastewater.In PMS/coprecipitation Sb-CuFe₂O₄@GO system,the reaction efficiency was greatly affected by catalyst and PMS dosage.The high degradation efficiency and low cost could be achieved in the presence of 0.15 m M PMS and 0.025 g/L catalyst.Radical quenching and ESR tests suggested that SO₄·^-and hydroxyl radical（·OH）,especially the former played a dominant role in PMS/Sb-CuFe₂O₄ system.Possible catalysis mechanism was proposed based on X-ray photoelectron spectroscopy analysis,indicating that the surface hydroxyl groups and the interactions among surface metal species,oxygen species,and PMS were critical for maintaining high catalytic activity.Based on intermediate identification by UPLC/QTOF-MS analysis,TBBPA degradation pathway was proposed.Radical quenching tests implied that SO₄·^-was the main active species in PMS/Sb-CuFe₂O₄@GO system,and ·OH also participated in the oxidation process.According to all the results,spinel Sb-CuFe₂O₄ performed higher catalytic ability than the undoped,maintained good performance in a wide pH range and actual wastewater,and exhibited favorable reusability and stability.Moreover,loading SbCuFe₂O₄ onto GO by coprecipitation method could further improve its catalytic ability,which provides a new possibility for the preparation of catalysts activating PMS.