Study On Preparation Of Mesoporous Molecular Sieve Based Heterogeneous Fenton Catalysts And Its Catalytic Performance

Heterogeneous Fenton catalysts are usually used to treat the wastewater which contains many kinds of e refractory organics.Compared to other techniques,treatment of the wastewater with heterogeneour Fenton catalysts has the superiority of less sludges production,easier catalyst recycling,lower operation cost and no secondary pollution.The preparation of efficient and stable heterogeneous Fenton-like catalysts is most important and the key factor in the process of actual application.In our work,mesoporous MCM-41 and active Fe-Mn loaded MCM-41（Fe-Mn/MCM-41 nanocomposites）,were prepared by hydrothermal and impregnation method respectively.The physicochemical characteristics of the synthesized samples were evaluated by various techniques such as XRD,SEM,TEM,nitrogen physisorption,FT-IR and XPS.The results show that the framework was slightly destroyed after the loading of iron and manganese species onto the MCM-41 surface.But the main structures were preserved.Fe loading of around 5 wt%and mole ratio of Fe and Mn at 1:1 was confirmed as the optimal loading amount through degradation experiments.The experimental results confirmed the excellent absorption property of catalysts to the organics.The experiments of MO degradation were carried out to assess the performance of catalysts in the Fenton reactions.The results show that slight removal of MO by MCM-41 and Mn/MCM-41 with H₂O₂ was mainly attributed to the surface adsorption of nanocomposites.Compared with Fe/MCM-41,the removal of MO with Fe-Mn/MCM-41 is apparently higher.The optimal reaction conditions have been got by changing reaction conditions of heterogeneous Fenton reaction process.The catalytic ability of Fe/MCM-41 was higher than nanometer sized Fe₂O₃,which indicated the role of MCM-41 in degradation process.But the degradation rate of the heterogeneous Fenton was still lower than that of homogeneous Fenton.Reaction mechanism was studied based on experiments.·OH were verified to be the main reactive species produced during Fenton-like process,and both heterogeneous and homogeneous Fenton reaction work in the process of the MO degradation,but the heterogeneous reaction played a dominant role in the rapid oxidation of MO.According to the results and previous research,we can draw conclusions that as a transition metal ion with variable valence,manganese species may participate in the chain reaction of radicals in Fe（III）/H₂O₂ system by producing Fe（II）,which can affect the efficiency of Fe（III）/H₂O₂ system ultimately.This can explained the synergy between Fe（III）species and Mn（IV）species in promoting MO degradation.Kinetic studies show that the degradation process of MO obeyed first-order kinetic model.The mineralization ability and recyclabil ity of Fe-Mn/MCM-41 was tested and the excellent performance was demonstrated.