Studies On The Heterogeneous Fenton-Like Reactions Catalyzed By CeO₂ With Different Morphologies And Loaded Onto Porous Al₂O₃

The problem of environmental water pollution has seriously endangered human health.Heterogeneous Fenton-like oxidation technology is one of the effective means for sewage treatment,which has the characteristics of wide p H range,high catalytic efficiency and high utilization rate of H₂O₂.This paper took cerium oxide（CeO₂）as the research object,different morphologies of CeO₂ and porous Al₂O₃ supported CeO₂（CeO₂/Al₂O₃）were prepared.X-ray diffraction（XRD）,scanning electron microscopy（SEM）,transmission electron microscope（TEM）,Fourier transform infrared spectroscopy（FT-IR）,X-ray photoelectron spectroscopy（XPS）,surface area and pore size analyzer were used to characterize different morphologies CeO₂ and CeO₂/Al₂O₃.In this paper,methyl orange（MO）was used as the target pollutant to systematically study the influencing factors,optimal conditions and possible mechanisms of CeO₂ and CeO₂/Al₂O₃ catalyzing heterogeneous Fenton-like reaction.Rod,spheres and cluster CeO₂ showed good degradation performance for MO.Spheres and clusters have good adsorption properties for MO.The results of single factor experiment showed that the Fenton-like reaction efficiency decreased with the increase of p H value,H₂O₂ dosage and MO concentration;as the amount of catalyst increased,the Fenton-like reaction efficiency increased.Response surface analysis（RSM）was used to optimize the conditions of heterogeneous Fenton-like reaction.The results showed that there were significant interactions between the initial p H value and the catalyst,and between the concentration of H₂O₂ and the amount of catalyst.The optimal conditions determined by RSM method were as follows:initial p H=2.3,initial MO concentration 15.5 mg/L,initial H₂O₂ concentration 41.6 m M,and CeO₂ dosage 1.4g/L.Under this condition,the decolorization rate of MO could reach 95.42%within 1hour.Free radical capture experiment found that singlet oxygen（¹O₂）played the main catalytic degradation effect.For CeO₂/Al₂O₃,the more ammonium chloride was used as pore-forming agent,the greater the specific surface area of Al₂O₃ was,and the better the catalytic Fenton-like reaction efficiency of CeO₂/Al₂O₃was.In addition,Fenton-like reaction efficiency was also closely related to CeO₂ load.The study found that 50%CeO₂/Al₂O₃catalyzed Fenton-like reaction efficiency was the best.The results of single factor experiment showed that the Fenton-like reaction efficiency decreased with the increase of p H value and MO concentration;with the increase of H₂O₂ dosage,the efficiency of Fenton-like reaction first increased and then decreased;as the amount of catalyst increased,the Fenton-like reaction efficiency increased.When the initial p H=2,H₂O₂concentration 19.58 m M,50%CeO₂/Al₂O₃ dosage 0.5 g/L,and MO initial concentration 40 mg/L,the decolorization rate of MO can reach 98.52%within 1 hour.Kinetic analysis showed that the catalytic efficiency of CeO₂/Al₂O₃ in Fenton-like reaction was in accordance with the first-order kinetic equation.The mechanism study found that in the catalytic Fenton-like reaction,Ce⁴⁺,hydroxyl radical（·OH）,superoxide radical（O₂·-）and peroxy hydroxyl radical（HO₂·）interact to produce ¹O₂ to catalyze the degradation of organic pollutants.Ce³⁺was involved in Fenton-like reaction,and part of Ce³⁺was converted to Ce⁴⁺after the reaction.