Preparation And Properties Of Iron-based Semiconductor Heterojunction Photo-fenton Catalysts

With the rapid development of industry and agriculture,more and more organic pollutants,such as dyes,pesticides,and antibiotics,have been discharged into water bodies,causing serious water pollution problems.These organic substances are chemically stable,complex in structure,highly toxic,and difficult to be degraded.The Fenton method has the advantages of simple operation,mild reaction condition,and low cost,and thus is widely used in the treatment of organic wastewater.However,the homogeneous Fenton reaction has the disadvantages of narrow p H range,acidic condition,formation of iron sludge,and difficulty of recycling the catalyst.The heterogeneous Fenton reaction solves the above problems of the homogeneous one,for example,the reaction can be carried out in a wide p H range and the catalyst can be recycled.However,the catalyst still has problems such as low activity and metal leaching.Therefore,the design and preparation of heterogeneous Fenton catalysts with high activity and high stability has become one of the important research directions of heterogeneous Fenton technology.Semiconductor photocatalysis is also one of most promissing sewage treatment technologies with great application prospects due to its advantages of low cost and environmentally friendliness.By coupling a semiconductor and an iron-based Fenton catalyst to construct a photo-Fenton catalyst,the activity of the catalyst can be effectively improved.The Fe-Bi₂WO₆/Ti O₂ heterojunction composite material（Fe5BW-AT）was prepared by combining iron-doped bismuth tungstate and titanium dioxide by electrostatic self-assembly,and the mechanism of the photo-Fenton reaction was studied.XRD,FT-IR and SEM proved the successful construction of heterojunction.Experimental results show that Fe5BW-AT removes 96.2%of methylene blue（MB）in 70 min,and the degradation efficiency remains 89.6%after three cycles.Through control experiments,it was found that the photo-Fenton reaction rate constant was much larger than the sum of the rate constants of the dark Fenton reaction and the photocatalytic reaction.This is due to the synergistic effect of Fenton oxidation and photocatalysis,and the photogenerated electrons generated by the photocatalytic process promote Fe³⁺/Fe²⁺cycles,therefore,the catalyst maintains good reaction performance.The Fe₂O₃/CN/Ti O₂ ternary heterojunction material was prepared by one-step pyrolysis of the mixture of Fe-MOF（MIL-53）,Ti-MOF（NH₂-MIL-125）and urea.The experimental results show that when the mass ratio of Fe:Ti:urea is 0.05:0.1:10,the catalyst Fe0.5Ti CN exhibits the best photo-Fenton reaction performance.After 40 minutes of reaction,98.2%of MB was removed.The degradation efficiency still maintained 95.7%after three successive runs.The catalyst has universal applicability as a photo-Fenton catalyst and can efficiently degrade various organic pollutants（dyes and antibiotics）.The excellent photo-Fenton reaction performance of the catalyst benefits from the construction of a heterojunction,which promotes the separation and transfer of photo-generated electrons and holes.The photo-generated electrons accelerate the Fe³⁺/Fe²⁺cycle,and at the same time further improve the charge separation efficiency.The synergistic effect of photocatalysis and Fenton reaction enables the catalyst to efficiently degrade organic pollutants.