Preparation Of Modified Iron-based MOFs And Their Catalytic Degradation Of Tetracycline Antibiotics

The ecological issues caused by the widespread use of antibiotics have attracted wide attention,as the continuous development of clinical medicine,animal husbandry,aquaculture and other fields.Antibiotics eventually enter natural water bodies through the discharge of medical,pharmaceutical wastewater and biological metabolism.As an emerging contaminant in the water environment,antibiotics are more difficult to treat owing to their strong hydrophilicity,lower volatility and complex composition,which seriously affect the living environment of humans and other organisms.Therefore,it is imperative to explore an efficient remediation technology for antibiotic pollution.Combining photocatalytic technology with Fenton process is a very promising strategy to degrade antibiotics in the aqueous environment.In this dissertation,the sources and hazards of tetracycline antibiotics in the aqueous environment are discussed,and the deep treatment technologies currently available for tetracycline antibiotics are described,analyzed and compared in detail from the perspectives of operating conditions and treatment effects.Oxytetracycline hydrochloride and tetracycline hydrochloride were selected as the degradation targets.The main catalyst for the photo-assisted Fenton-like system to degrade tetracycline antibiotic simulated wastewater was an iron-based metal organic framework,which was compounded with three carbon components and transition metal oxides,respectively.Moreover,the corresponding mechanism and pathway of degradation were hypothesized.The following are the primary research findings:1.Carbon materials of different dimensions were prepared and pretreated individually.The CQDs@NH₂-MIL-101（Fe）,MWCNTs/NH₂-MIL-101（Fe）and r GO/NH₂-MIL-101（Fe）were prepared by the solvothermal method.The effects of the introduction of carbon quantum dots（CQDs）,functionalized multi-walled carbon nanotubes（MWCNTs）and reduced graphene oxide（r GO）on the photo-assisted Fenton-like properties of NH₂-MIL-101（Fe）were investigated.The results showed that under the conditions of MWCNTs/NH₂-MIL-101（Fe）addition of 10 mg,H₂O₂ concentration of 2m M and p H～7,the degradation efficiency of the composite catalyst at 10%MWCNTs content was about 90%for 20 mg/L oxytetracycline hydrochloride within 30 min.While r GO/NH₂-MIL-101（Fe）addition of 10 mg,H₂O₂ concentration of 4 m M and p H～4,the degradation efficiency of the composite catalyst at 15%GO content in the precursor also reached nearly 90%within 30 min.And the addition of CQDs can make the NH₂-MIL-101（Fe）material a fluorescent probe for recognizing Fe³⁺,which broadens the application scope of NH₂-MIL-101（Fe）.The possible degradation mechanism of oxytetracycline hydrochloride was speculated by physical and chemical characterization,and the reactive oxygen species was detected.Finally,the stability of the composite catalyst was investigated by cycling experiments.2.α-Fe₂O₃/MIL-53（Fe）composite catalysts were prepared by a two-step solvothermal method with the addition of different ratios of formic acid for the photo-assisted Fenton-like system to activate H₂O₂ for the degradation of tetracycline hydrochloride simulated wastewater.Characterization of the components and structures of the materials by a series of techniques such as XRD,FT-IR,SEM and TEM showed the synergistic effect betweenα-Fe₂O₃ and MIL-53（Fe）and also confirmed the existence of coordination unsaturation sites（CUSs）within the main catalyst of MIL-53（Fe）.A series of experiments were designed to investigate the reaction mechanism and the optimal reaction conditions,the degradation efficiency of tetracycline hydrochloride can reach 96.9%within 40 min when the amount of catalyst is 10 mg,the p H of solution is 5and the consumption of H₂O₂ is 4 m M.The response surface methodology was used to verify the optimal reaction conditions as well.The stability and reproducibility of the catalysts were explored through comparing of catalyst activity before and after rection and cycling experiments.Based on the experimental results and data such as the capture of reactive oxygen species,the possible degradation pathway and mechanism were analyzed and proposed.