| The strict pH range limits,low visible light utilization and difficulty in separation of catalyst are often outlined as the major drawbacks of the homogeneous photo-Fenton process,therefore it's difficult to apply in practice.Heterogeneous photo-Fenton method is considered as a promising alternative approach for the treatment of organic pollutants because it could effectively overcome the above shortcomings.MIL-101(Fe),as a kind of porous materials with large specific surface area and abundant active sites,has been intensely studied in catalysis.Additionlly,Ag/AgCl have also attracted widespread interest due to its high photo catalytic ability under visible light as a result of their surface plasmon resonance.In this paper,in order to further improve the visible light utilization efficiency of MIL-101(Fe),a novel photo-Fenton catalyst named Ag/AgCl/MIL-101(Fe)was synthesized by coupling these two materials.The as-parpered catalyst was tested as heterogeneous photo-Fenton catalyst for methylene blue(MB)degradation under visibe light irradiation and neutral pH,and the following conclusion was reached:(1)Ag/AgCl/MIL-101(Fe)photo-Fenton catalyst was synthesized for the first time by the method of precipitation and photo reduction.The results of X-ray diffraction(XRD),Fourier infrared spectroscopy(FTIR),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDX),X-ray photoelectron spectroscopy(XPS)and thermogravimetric curve(TG-DSC)reveal that Ag/AgCl was loaded on the MIL-101(Fe)successfully.The result of diffuse reflectance UV-vis spectroscopy(DRS)shows that Ag/AgCl/MIL-101(Fe)can efficiently absorb visible light;The results of the nitrogen adsorption-desorption isotherms indicated that the BET specific surface area and pore volume of MIL-101(Fe)were somewhat decreased after immobilizing Ag/AgCl,resulting from the effect of pore blocking by the Ag/AgCl particles.(2)The Plackett-Burman design(P-B)was used to screened the key factors which influent MB degradation in the photo-Fenton process.Box-Behnken design(BBD)was employed to optimize the reaction conditions.The optimal condition for MB removal was found as initial methylene blue of 10.72 mg/L,catalyst dosage of 0.97 g/L,initial H2O2 concentration of 10.90 mM and radiation intensity of 457.79 W.Under this condition,the maximum MB decolorization efficiency and total organic carbon(TOC)removal efficiency could reach to 99.75%and 65.43%s respectively.After six repeated reactions,the MB decolorization efficiency can still be kept at 92.1%,indicating that the catalyst has good stability.(3)The capture tests were used to find out the active species in the MB degradation process.Meanwhile,Combining Photoluminescence spectroscopy(PL)of Ag/AgCl/MIL-101(Fe)and the results the ESR measurements,we proposed the mechanism for the photo-Fenton degradation of MB over Ag/AgCl/MIL-101(Fe). |
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