Study On Synthesis Of Graphene Oxide/Fe-MOF Derivatives And Activated PS For Catalytic Degradation Of 2,4,6-Trichlorophenol

The refractory organic pollutants of halogenated aromatic hydrocarbons in water environment have the characteristics of low concentration,wide distribution range,and strong biological enrichment.In addition,the catalytic activity of the catalyst in the existing catalytic system is limited,and the release of sulfate radicals generated by the activation of PS.After that,free radicals cannot be quickly transferred to the pollutants to be fully utilized,which leads to the problem that the oxidative degradation efficiency of the pollutants decreases.In this project,halogenated aromatic hydrocarbon pollutants are used as representative targets,and Fe-based metal organic framework?Fe-MOF?and graphene oxide?GO?are the objects.First,graphene oxide/metal organic framework composite GO/Fe-MOF was synthesized.Then,for the low initial reaction rate and the need to further improve the catalytic efficiency,the calcination method using GO/Fe-MOF as precursor is used to further optimize and organize the structure and performance of the catalyst.First,one-pot solvothermal method was used to prepare the reduced graphene oxide/metal organic framework?RGO/MIL-101?Fe??.The synergistic effect between RGO and MIL-101?Fe?in the composite catalyst and the catalytic activity were investigated and analyzed.With2,4,6-trichlorophenol?TCP?as the target pollutant molecule,the catalytic performance of the composite material and the effect of reaction parameters on the catalytic activity were studied.It can be concluded that the catalytic activity of RGO/MIL-101?Fe?is significantly enhanced compared to pure MIL-101?Fe?and RGO alone,and the reaction rate constant reaches 6.64×10^-2 min^-1.The results show that when the reaction conditions are:RGO?5%?/MIL-101?Fe?catalyst dosage was 0.5 g·L^-1,the initial p H was 5.0,PS concentration was10mmol·L^-1 and TCP concentration was 20mg·L^-1,TCP removal rate reached 92%at 180 min,which also showed that the catalyst had good catalytic activity in a wide p H range.The physicochemical properties of RGO/MIL-101?Fe?and the effect of the surface interaction between MOF and RGO sheet on the catalytic activity were characterized and studied through various methods.The results showed that the catalytic efficiency of RGO/MIL-101?Fe?is higher than that of MIL-101?Fe?,thanks to its more active sites and good electron transfer performance.Secondly,on the basis of this study,we prepared graphene-supported iron nanoparticles/nitrogen-doped porous carbon Fex CN@GN hybrid materials by using high-temperature pyrolysis GO/NH₂-MIL-101?Fe?.The introduction of active sites including Fe⁰,Fe???and doped nitrogen in the catalyst,as well as the advantages of the multi-stage pore structure obtained after the cooperative pyrolysis,which made the purpose of efficient catalytic PS possible.The reaction rate of the product Fex CN@GN obtained after pyrolysis is significantly enhanced,which is 14 times the reaction rate of MIL-101?Fe?.By characterizing the physicochemical properties of the samples before and after pyrolysis,the effects of various regulatory factors,including doped N atoms,pyrolysis procedures,and graphene supports on the structure and performance of the catalyst were analyzed.It can be concluded that after the precursor GO/NH₂-MIL-101?Fe?is calcined,the Fe-O in the metal organic framework compound is converted into metal nanoparticles such as Fe₂O₃,Fe₃O₄ and Fe⁰,and the amino functional group is converted into different types of nitrogen defective active sites.Fe?II?and zero-valent iron can directly react with persulfate,effectively increasing the initial rate of reaction.Graphite nitrogen,pyrrole nitrogen,and Fe-N formed by the doping of nitrogen atoms as active sites also effectively improve the catalytic activity of the catalyst Fex CN@GN.After the precursor GO/NH₂-MIL-101?Fe?is calcined,the pore structure where micropores and smaller mesopores coexist transformed into a multi-level pore structure dominated by larger mesopores,which improves the mass transfer efficiency of active substances and target pollutants molecule.As support,graphene is not only conducive to electron transfer,but also effectively traps free radicals and restricts them to the surface of the catalyst.It is conducive to the direct in situ reaction of free radicals and pollutant molecules adsorbed on the surface,and the catalytic degradation efficiency of TCP significantly improved.