Core-shell Structured Fe₃O₄@GO@MIL-100?Fe? Magnetic Nanoparticles As Heterogeneous Photo-fenton Catalyst For 2,4-dichlorophenol Degradation Under Visible Light

Heterogeneous photo-Fenton is a kind of advanced oxidation process.Owing to its strong oxidation of hydroxyl radicals,it is commonly used to degrade various refractory organic pollutions.Magnetic porous materials are widely used in heterogeneous Fenton system due to their magnetic separation and catalytic properties.However,there is a defect of slow Fe?III?/Fe?II?conversion in the heterogeneous photo-Fenton method.In order to solve this problem,a kind of core-shell structured Fe3O4@GO@MIL-100?Fe?heterogeneous photo-Fenton catalyst with Fe3O4 as core,GO?graphene oxide?as interlayer and MIL-100?Fe??a kind of Metal organic frameworks?as shell was prepared.The crystal structure,morphology,catalytic activity and mechanism of the catalyst were systematically studied.The experimental contents and results are as follows:?1?The core-shell structured Fe₃O₄@GO@MIL-100?Fe?heterogeneous photo-Fenton catalyst was successfully prepared by hydrothermal method.The crystal structure,morphology,surface chemical properties of the catalyst were analyzed by by XRD,Raman,SEM,TEM,XPS,BET and magnetic saturation test.XRD and Raman results showed that Fe3O4/GO/MIL-100?Fe?catalyst was successfully prepared;SEM and TEM demonstrated that the catalyst has a core-shell structure with particle size ranging from 360⁴10 nm,in which the thick of shell MIL-100?Fe?is about 61 nm and GO is about 4.5 nm;XPS indicated that the chemical composition of the catalyst surface varied with the encapsulating material;BET measurement showd that the Langmuir surface area of Fe₃O₄@GO@MIL-100?Fe?is 1048.1 m²/g,with a mixed microporous and mesoporous structure;The magnetic saturation strength of catalyst is 67.9 emu/g.?2?Catalytic performance of Fe₃O₄@GO@MIL-100?Fe?was investigated using2,4-dichlorophenol?2,4-DCP?as the target pollutant.Comparing six catalysts,Fe₃O₄@GO@MIL-100?Fe?,Fe₃O₄@MIL-100?Fe?,MIL-100?Fe?,Fe₃O₄@GO,Fe₃O₄and Fe₃O₄@MIL-100?Fe?+GO for the degradation of 2,4-DCP,the results showd that the degradation rate of 2,4-DCP by Fe3O4@GO@MIL-100?Fe?was significantly better than other catalysts.The optimum experimental conditions were obtained by experiments of influencing factors.At pH 5.5,H2O2 3 mmol/L,Fe3O4@GO@MIL-100?Fe?0.2 g/L,illumination intensity 500 W and 2,4-DCP 50mg/L conditions,2,4-DCP could be completely degraded in 40 min,and its mineralization rate reached 61%,the utilization of H₂O₂ is 74.8%at 180 min.?3?The mechanism of the reaction system was studied by means of trapping experiment of active species,electron spin resonance,photoluminescence spectroscopy and electrochemistry.The capture experiments of active species showed that hydroxyl radicals was the main active species in this system,but superoxide radicals and holes were also important radicals.Based on the literature,we proposed the simplified reaction mechanism of the system.Finally,the intermediate products of2,4-DCP degradation were detected by gas chromatography-mass spectrometer,and the degradation pathway of 2,4-DCP was speculated.