Enhanced Catalytic Degradation Of Emerging Organic Contaminants By A Functional Bismuth Ferrite Nanostructure Material

Emerging Organic Contaminants（EOCs）are currently hot research topics in the field of environmental chemistry.They come from industrial additives,pesticides,drugs and personal care products.They are organic substances that have not been effectively managed and controlled.In the process of production and use,EOCs enter the environmental ecology in various ways.They often exhibit persistence and high risk.They have the potential to cause unknown ecological toxicological effects and human health hazards.Advanced Oxidation Technology（AOPs）is now the most concerned organic pollutant treatment technology.Among them,Fenton’s reagent method has the advantages of simple equipment,mild conditions and high reaction efficiency,and can be used for organic pollution that is difficult to degrade by general chemical or biological methods It has been widely used.However,the traditional Fenton’s reagent method mainly has the following major problems in practical application:1)The effective working p H value is around 3;2)The continuous addition of ferrous iron salts results in a large amount of iron sludge.The existence of the above problems has caused high post-processing costs and secondary environmental pollution.In response to these problems,this study started with catalysts and optimized catalytic systems.By preparing a new and highly efficient bismuth ferrite allotropic phase composite（BF-PMCs）,a heterogeneous phase with BF-PMCs as the catalyst was constructed The（photo）Fenton-like catalytic system can effectively degrade various types of new organic pollutants under near-neutral p H conditions,and study the degradation pathway mechanism of its representative EOCs.In this study,bismuth ferrite allotrope composite catalyst materials（BF-PMCs）were successfully prepared by low-temperature co-precipitation integrated hydrothermal method.The physical and chemical properties such as phase structure,specific surface area,morphological structure,element composition and surface atomic valence state of BF-PMCs were characterized by XRD,N₂ adsorption and desorption,SEM,EDX,TEM and XPS.The results show that the BF-PMCs catalyst is a polycrystalline phase composite catalytic material composed of mullite bismuth ferrite（90.6%Bi₂Fe₄O₉）and a small amount of perovskite bismuth ferrite（9.4%Bi Fe O₃）.The iron content,particle size distribution is uniform,regular square sheet-like nanostructure characteristics（side length of cluster body～400 nm,thickness～80 nm）.Therefore,it will have a larger specific surface area and more active sites than its bulk material.In the following research,EOCs such as SMX,AZX,BPA and 2,4-DCP as the target pollutants,a heterogeneous Fenton（BF-PMCs/H₂O₂）catalytic degradation system with BF-PMCs as the catalyst was first constructed.Through the adjustment of p H,H₂O₂ initial concentration,pollutant initial concentration and BF-PMCs dosage and other influencing factors,the optimized system conditions were obtained as p H～4.5,H₂O₂ initial concentration 70 m M,pollutant initial concentration 1.5 mg L^-1 and BF-PMCs dosage 0.2 g L^-1.Based on the optimization system,the application research on the degradation effects of the above target pollutants was carried out,and the degradation rates reached 94.1,98.7,81.2,and 89.8%,respectively.Represented by SMX,combined with free radical scavenger and fluorescence technology,it was detected that HO^?free radical is the main type of free radical,and the degradation process was successfully detected by high performance liquid chromatography-mass spectrometry（HPLC-MS）and ion chromatography.The resulting intermediate products,organic acid radicals（acetic acid,pyruvate）and inorganic anions（sulfate,nitrate）,further speculate that SMX has four degradation paths in the BF-PMCs/H₂O₂system.Based on the multi-phase Fenton-like system established above,this study is derived from a visible light-driven photo-Fenton catalytic system（LED/BF-PMCs/H₂O₂）.Through carrying out catalytic degradation studies on AZX,TC,Ci FX,EBP,DMP,DBP,Estrone,DBDPO,DCP,IBU,ISU,Thiacloprid,BPA,TPA,Nap,SMX,LOX and other EOCs target pollutants,they were evaluated Potentially strong application in organic pollutants.In this chapter,we conducted an applied study on the main reaction condition parameters（such as p H,initial H₂O₂concentration,etc.）to optimize the visible light Fenton catalytic system and clarify its effect on the catalytic degradation efficiency.Through research,the optimal conditions of the system are p H～4.5,initial concentration of H₂O₂ 10 m M,initial concentration of pollutants 0.5 mg L^-1 and the dosage of BF-PMCs 0.2 g L^-1,it is not difficult to find that the introduction of visible light is greatly reduced The amount of hydrogen peroxide added（reduced by nearly 86%）,and through research found that organic pollutants can be degraded more quickly.In the study,we simulated the inorganic anions(Cl^-,NO₃^-)and small organic acid radicals（such as humic acid）present in the natural water system and found that they have a certain negative effect on the catalytic degradation system.Further optimization.In addition,this chapter also carried out the identification research of free radicals in the system with the help of free radical scavengers and was further verified by electron spin resonance（ESR）.Finally,based on the optimized system,the degradation effects of various representative new organic pollutants under the LED/BF-PMCs/H₂O₂ system were studied.