Preparation Of Bismuth Ferrite Based Materials For Degradation Of Antibiotics

The antibiotics abuse not only causes great damage to the ecological environment,but also poses a great threat to aquatic organisms and human health.So,exploring efficient removal methods of antibiotics has become an important consensus in the field of environmental protection and ecological governance.Fenton oxidation technology has gradually become indispensable methods in the antibiotic treatment field attributed to various advantages,such as low treatment cost,high mineralization efficiency and simple operation process.Among them,the design and development of heterogeneous Fenton reaction system is regarded as the frontier research in pollution control chemistry field by overcoming intrinsic shortages of homogeneous Fenton reaction,as hydrogen peroxide（H₂O₂）squander,iron sludge enrichment pollution and harsh reaction environment.The antibiotic oxidation efficiency of heterogeneous Fenton reaction system is closely related to the Fe³⁺/Fe²⁺cycling efficiency and H₂O₂ utilization efficiency.Therefore,the design and construction of Fenton catalyst with high Fe³⁺reduction efficiency and strong activation ability of H₂O₂ is core of efficient antibiotics removal process.As a typical iron oxide,bismuth ferrite material can partially activate H₂O₂ to oxidize antibiotics,but it is significant to enhance the Fe³⁺/Fe²⁺cycle efficiency for boosting the H₂O₂activation ability and meeting with industrial requirements.Therefore,the formation of composites,surface modification and oxygen vacancy（OVs）construction are employed to accelerate the Fe³⁺/Fe²⁺cycle and H₂O₂ decomposition.The structure-activity relationship of the Fenton system microstructure and the antibiotic removal efficiency is investigated by establishing semi-quantitative method for analyzing the H₂O₂ activation efficiency.And the possible degradation path and reaction mechanism of Fenton oxidation of antibiotics were elucidated.The detail contents list as follows:（1）Bi Fe O₃,Bi₂Fe₄O₉ and Bi Fe O₃/Bi₂Fe₄O₉ composites were prepared by adjusting the calcination temperature.The construction of Bi Fe O₃/Bi₂Fe₄O₉ composite was conducive to increasing the electron density around the two-phase boundary for accelerating the conversion from Fe³⁺to Fe²⁺and enhancing the H₂O₂ decomposition efficiency to obtain more reactive oxygen species（ROS）.Under optimal conditions,the H₂O₂ utilization rate of Bi Fe O₃/Bi₂Fe₄O₉（22.8%）is 15.4%and 7.3%higher than that of Bi Fe O₃ and Bi₂Fe₄O₉,respectively.The removal efficiency of chlortetracycline hydrochloride（CTC）is up to 69.5%（60 min）in Bi Fe O₃/Bi₂Fe₄O₉/H₂O₂ system,which is 41.1%and 14.0%higher than that of Bi Fe O₃ and Bi₂Fe₄O₉,respectively.The possible degradation path and the reaction mechanism of Fenton removal of CTC is speculated by liquid chromatography-mass spectrometry（HPLC-MS）and electron spin resonance（ESR）spectroscopy.（2）Bi₂Fe₄O₉ nanosheets was prepared by sol-gel method and boric acid（H₃BO₃）modified Bi₂Fe₄O₉（H₃BO₃@Bi₂Fe₄O₉,BBFO）materials were prepared by H₃BO₃ surface modification with mechanical ball milling method.H₃BO₃ was successfully modified on the Bi₂Fe₄O₉ surface according to various characterization.Electron spin resonance（EPR）results show that OVs can be introduced into Bi₂Fe₄O₉ surface by H₃BO₃ modification.The presence of H₃BO₃ and abundant OVs is conducive to the surface electrons accumulation and transfer for strengthening the Fe³⁺/Fe²⁺cycle and H₂O₂ decomposition.The degradation efficiency for oxytetracycin（OTC）of BBFO-2 materials reached 75.0%within 60 min,which was 21.8%higher than that of Bi₂Fe₄O₉（HBFO）without H₃BO₃ modification.And the H₂O₂ utilization rate（23.4%）of BBFO-2 materials is higher than that of Bi₂Fe₄O₉（7.6%）.The possible degradation path and reaction mechanism of Fenton oxidation of OTC were speculated by ESR and HPLC-MS analysis.（3）Cubic-like bismuth ferrite(Bi₂₅Fe O₄₀-H)with a small amount of OVs and OVs-rich bismuth ferrate(Bi₂₅Fe O₄₀-B)nanoparticle were synthesized by hydrothermal and mechanical ball milling method,respectively.The abundant OVs on Bi₂₅Fe O₄₀-B surface is conducive to boost the H₂O₂ adsorption/activation process.And the H₂O₂ utilization rate of Bi₂₅Fe O₄₀-B materials is up to 55.3%,which is beneficial for promoting the production capacity of ROS species.Therefore,the TCH degradation rate of Bi₂₅Fe O₄₀-B materials reaches 84.1%（120 min）,which is 2.2 times that of Bi₂₅Fe O₄₀-H materials.The possible TCH degradation paths and reaction mechanism of Fenton oxidation TCH were speculated by ESR and HPLC-MS spectra.