Preparation Of Variable Metal Fe/Co Oxide Catalysts And Performance For Photo-Fenton Degradation Of Tetracycline

Tetracycline（TC）is now widely used in livestock,aquaculture and medical industries,and is one of the most demanded and used antibiotics in these industries.Although the TC effluent discharged from related industries is treated to meet the standard and discharged,there is still a certain concentration of undegraded TC,resulting in the enrichment of TC in the environment,thus causing pollution to the environment and posing a serious threat to human health.How to solve TC pollution from the source and degrade it completely and efficiently to reduce the damage to environmental biological system and human health is an important issue that needs to be solved urgently in the current society.Therefore,it is urgent to find an efficient wastewater treatment technology.In recent years,the photo-Fenton technology has been widely used in the field of TC wastewater treatment for its high efficiency in treating pollutants and achieving complete mineralization of many complex pollutants,which has been favored to a high degree.However,there are some limitations in the practical use of this technology,such as low visible light utilization,narrow p H applicability range,difficult separation and recovery,and long degradation time,etc.By developing a low-cost and structurally stable environment-friendly catalyst is the core of driving the photo-Fenton technology to degrade TC and solve the technical limitations.In this thesis,the development of variable metal Fe/Co oxide photocatalyst materials is the main research content,and the degradation performance of the prepared specific series of catalysts to excite the photo-Fenton reaction for TC is investigated,and the photo-Fenton degradation mechanism of different catalysts for TC is elaborated.The paper includes the following sections:Firstly,we introduce TC wastewater and treatment technologies:firstly,we explain the migration mechanism of TC sources and the hazards caused by TC pollution;secondly,we give a brief overview of the current common TC wastewater treatment technologies,with emphasis on the concept of Advanced Oxidation Process（AOP）and its application in the field of TC wastewater treatment;thirdly,we give a brief overview of the application of photo-Fenton technology in the field of TC wastewater treatment;finally,we give a brief overview of variable metal oxides and their application.Finally,a brief overview of variable metal oxides and their applications was given.Secondly,the environmentally friendly natural clay mineral halloysite nanotubes（HNTs）were introduced into the Co Fe₂O₄nanoparticle precursor solution by a one-step solvothermal method,and the HNTs@CFO series photocatalyst materials were successfully prepared by varying the introduction ratio of HNTs.XRD,TEM,Mapping,XPS,BET,UV-Vis DRS and the photocatalysts were characterized by XRD,TEM,Mapping,XPS,BET,UV-Vis DRS and EIS,and applied to the photo-Fenton degradation of TCs.The results showed that Co Fe₂O₄nanoparticles were uniformly loaded on the surface of HNTs nanotubes,and the fixation was very stable,and the unique tubular structure and large surface area of HNTs did improve the problem of easy agglomeration of nanoparticles.It was found that the degradation performance of the obtained catalysts was optimal when the HNTs introduction ratio was 0.5,and the degradation rate of TC reached 90.5%in 2 min and 98.3%in 30 min,meanwhile,the catalysts had excellent degradation universality,reusability and structural stability.Thirdly,Co Fe₂O₄nanoparticles were synthesized by a modified solvothermal method and then dispersed in Bi₂Mo O₆precursor solution.Secondly,a new type of heterojunction material,CFO@BM series catalyst,was successfully obtained by secondary solvothermal reaction,which led to size increase material reorganization phenomenon and formation of larger size Bi₂Mo O₆microsphere morphology,and in situ assembly of Co Fe₂O₄nanoparticles into the formed Bi₂Mo O₆microspheres.The morphological and structural characterization was carried out by XRD,SEM,EDS,XPS,BET,UV-Vis DRS and EIS,and the performance of the photo-Fenton degradation TC was investigated and the degradation mechanism was explored.It was found that the photofenton degradation performance of the obtained catalyst（CFO@BM-0.15）was optimal when the amount of Co Fe₂O₄was added at 0.15 g.The photofenton degradation of TC was achieved within 90 min at 98.5%.It achieved98.3%of TC degradation within 90 min,and it also has good degradation universality,reusability and structural stability.Finally,Bi OCl nanoplates were firstly prepared by hydrothermal method and dispersed into the FQDs precursor solution.After the modification of FQDs anchored on the surface of Bi OCl nanoplates by in situ impregnation,the catalysts were prepared by changing the introduction ratio of FQDs,and the FQDs@Bn Ps series of heterojunction catalytic materials were successfully prepared.The structural morphology and photoelectrochemical properties were characterized by XRD,TEM,Mapping,XPS,BET,UV-Vis DRS and EIS,and applied to the photo-Fenton degradation of TC,and the mechanism of TC degradation was explored.It was found that the performance of the obtained catalyst（FQDs@Bn Ps3）for the photo-Fenton degradation of TC was optimal when the introduction ratio of FQDs was 3.The TC degradation rate reached 90.1%within 15 min,and 99.9%of TCs were degraded within 90 min,which itself also has excellent reusability,structural stability and degradation universality.The degradation pathways of TC were also discussed.In summary,this study enables the development of variable metal oxide photocatalyst materials,overcoming the problems of low visible light utilization,narrow p H applicability range,difficult separation and recovery,and long degradation time,which are prone to occur in the practical application of photo-Fenton technology.The prepared catalyst materials are expected to be applied in the field of TC wastewater treatment,providing a new method and reference for the fundamental treatment of high concentration TC wastewater pollution,and also laying the theoretical foundation for the development of new photo-Fenton catalysts to further broaden the application field of variable metal oxides.