Study On Photocatalytic-fenton Synergistic Degradation Of Antibiotics By BiFeO₃ Composite

With the rapid development of industry and agriculture,the problem of water pollution has become increasingly prominent.A large number of antibiotics are discharged into wastewater,and their residues pose a potential threat to the health of organisms and humans.Fenton technology and photocatalysis technology can effectively remove organic pollutants in water,which has attracted widespread attention.Traditional homogeneous Fenton technology has high p H requirements and difficulty in recovering iron ions,so heterogeneous Fenton technology has come into people's field of view.Its application is limited due to low utilization rate of H₂O₂and slow reduction rate of Fe³⁺to Fe²⁺.The application of photocatalytic technology is also limited due to the low utilization rate of sunlight and the easy recombination of photoelectron-hole pair.To some extent,photocatalysis-heterogeneous Fenton coupling technology solves these problems.When light is irradiated onto the semiconductor catalyst,the electrons excited by visible light are transferred to the Fenton reaction,which promotes the reduction of Fe³⁺to Fe²⁺,and accelerates the Fenton reaction cycle.At the same time,it also effectively suppresses the recombination of photogenerated electron-hole pairs and facilitates the photocatalytic reaction.This paper intends to use photocatalysis and Fenton oxidation technology to remove refractory organic pollutants efficiently.Two composite photocatalysts were prepared using visible light-responsive bismuth ferrite(BiFeO₃)as the matrix,and the morphology,composition and structure of the materials were analyzed through a series of characterization methods.Finally,the effect and mechanism of degrading organic matter by photocatalysis and Fenton reaction are discussed.The main research resultss are as follows:(1)The solvothermal-high temperature calcination method was used to synthesize BiFeO₃,which can obtain a large amount of BiFeO₃,and then the BiFeO₃/Bi OBr heterostructure was synthesized by chemical corrosion in situ method,and was used to explore the photocatalysis and Fenton's cooperative degradation of tetracycline performance.The results showed that under the conditions of p H=3,100?L H₂O₂,0.5g/L catalyst,the degradation rate of 50mg/L tetracycline reached91.41%after 80 min,and the apparent rate constant K was 0.0275min^-1.The reusability test and related test results show that after 5 times of recycling,the catalyst has a small amount of iron ion dissolution,stable properties,and good reusability.(2)BiFeO₃/g-C₃N₄/WO₃ternary spherical composites were synthesized by a one-step co-calcination method.Under visible light irradiation,the obtained ternary composites exhibited more effective photocatalytic-Fenton degradation performance than pure g-C₃N₄,WO₃,BiFeO₃and their binary composites.The results showed that under the conditions of p H=3,100?L H₂O₂and 0.5g/L catalyst,50mg/L tetracycline was basically completely degraded within 90min under the synergy of photocatalysis and Fenton.In addition,based on WO₃,g-C₃N₄,and BiFeO₃band gap structures,conduction band valence band positions,and free radical capture experiments,it was found that the charge transfer of BiFeO₃/g-C₃N₄/WO₃composites follows a direct solid Z-type mechanism.