Preparation Of Spinel Type Ferrate Photocatalyst And Its Performance In Degrading Of Tetracycline And Sulfamethazine Antibiotics In Water

Tetracycline hydrochloride?TC?and sulfamethazine?SMZ?have been widely used as a broad-spectrum antibiotic in medical and animal husbandry fields.However,they have widely penetrated into natural water bodies due to excessive use,causing serious harm to aquatic ecosystems and human health.Thus,the effective removal of TC and SMZ from water bodies is of great significance for maintaining the ecological environment and human health.Traditional treatment methods for antibiotics in water have encountered problems such as high energy consumption,low efficiency,more by-products,and difficulties in post-processing stage.In recent years,photocatalysis technology using solar energy has emerged,which can almost completely degrade organic pollutants and result in minimum secondary pollution.However,due to the narrow spectral response and low quantum efficiency of the designed photocatalytic materials,the practical application of this technology in the field of degradation of antibiotics is limited.Based on the factors that improve the photocatalytic performance of semiconductor materials,the modification of catalytic materials by coupling and morphology control were studied in this thesis.The evaluation on the photocatalytic efficiency for TC or SMZ was performed under visible light.The mechanism of the degradation was explored by means of liquid chromatography-mass spectrometry and electron paramagnetic experiments,so as to provide experimental and theoretical basis for the construction of highly efficient photocatalytic materials.Specific research results are as follows:?A porous hollow cubic ZnFe₂O₄ was synthesized by hydrothermal method using MOF Prussian blue as precursor.By using this catalyst under visible light,the degradation ratio of TC?40mg/L,100m L?in 70 minutes can reach 85%,which is significantly higher than that of the commercially available g-ZnFe₂O₄?degradation ratio 55%?and p-ZnFe₂O₄?55%degradation rate?prepared by co-precipitation.The relatively high degradation ratio of ZnFe₂O₄?l-ZnFe₂O₄?can be mainly attributed to its hollow structure,which can adjust the refractive index and enhance light scattering,which is beneficial to the degradation of organic pollutants.The optimal catalyst dosage was found to be 50 mg/L,and the optimal initial concentration of TC was 40mg/L.The catalyst has also been found to have some effects on degradation of other tetracyclines such as aureomycin?AM?and oxytetracycline?OTC?,but it has the best effect on TC,which may be due to the various structures of different antibiotics.HPLC-MS results showed that the degradation products of TC were CO₂,water and small inorganic molecules.?The CuFe₂O₄/MXene with Schottky junction structure was synthesized by means of semiconductor compound and was subjected to SMZ?40 mg/L,100 m L?degradation in the presence of visible light.The results show that in 60 minutes,CuFe₂O₄/MXene degrades SMZ up to 58%,whereas the degradation efficiency of the CuFe₂O₄ and MXene?Ti₃C₂?are only 11.5%and 3%,respectively.By characterizing the photoelectric properties of the monomer and composite catalysts and fitting the data of the time-resolved transient photoluminescence spectrum?TRPL?,it was found that the charge carrier's lifetime?7.02 ns?of CuFe₂O₄/MXene composite was longer than that of CuFe₂O₄ nanoparticle?6.69 ns?.In addition,the composite material has smaller charge carrier transmission resistance and higher photocurrent characteristics than any monomer mentioned above.The above results show that the Schottky junction formed by the introduction of MXene nanosheets improves the charge carrier's separation efficiency and greatly enhances the photocatalytic activity of the material.HPLC-MS and EPR are applied to an adsorption-degradation study for CuFe₂O₄/MXene Schottky junction and SMZ solution and the result suggest that SMZ undergoes N-S bond cleavage,hydroxylation,and aniline oxidation,etc.Finally,the intermediate products are further mineralized into CO₂,H₂O and other small molecular substances.?Heterojunction photocatalyst CaFe₂O₄/ZnCo₂O₄ was successfully synthesized by using a two-step method.When the mass ratio of the carrier ZnCo₂O₄ to CaFe₂O₄is 1:3?noted as ZC-30?,the heterojunction composite has the highest ratio of TC degradation.After 100 min light exposure,the TC degradation ratio reached 88%,which is higher than that of CaFe₂O₄ or ZnCo₂O₄,showing better photocatalytic activity.This photocatalyst also shows good performance in degradation of other tetracyclines such as AM and OTC.Notable that the degradation ratio of AM is 78%,which is slightly lower than TC.In addition,the photocatalyst CaFe₂O₄/ZnCo₂O₄showed high stability,specifically,almost no activity loss was observed after three photodegradation reaction cycles.The enhancement of photocatalytic activity is mainly due to the formation of the CaFe₂O₄/ZnCo₂O₄ heterojunction.This structure enables photo-generated electrons and photo-generated holes to be effectively separated,thereby fully utilizing the light irradiated on the catalyst surface,and greatly improving the catalytic activity of the composite catalyst.