Study On The ZnFe₂O₄ Preparation Optimization And Synergistic Catalytic Mechanism By Visible Light-permonosulfate To Degrade Ciprofloxacin

The abuse of antibiotics has led to their continuous migration and enrichment in the water environment.It enters the drinking water system,which would pose a potential threat to the human body and the ecosystem.Thus,people gradually realize the problem of antibiotics.The current traditional biochemical and physical removal methods need to take a long time and often fail to achieve true detoxification and mineralization.Photocatalytic oxidation technology is an energy-saving,efficient and safe water treatment technology,which has applicated prospects for the removal of antibiotics.ZnFe₂O₄ is an environmentally friendly spinel material with superior visible light response and moderate cost.Researchers have tried to modified the ZnFe₂O₄material to improve its photo-generated charge separation and transport performance.In this process,noble metal elements were introduced,which invisibly increases the application cost.In this regard,this study took the fluoroquinolone antibiotic CIP as the target pollutant,and introduced PMS as a charge transport intermediate,which improve the utilization of photogenerated charges at a lower cost and enhance the the PMS activation efficiency through the synergistic effect among visible light,PMS and ZnFe₂O₄.The research content mainly includes optimizing the control conditions for preparing ZnFe₂O₄ by hydrothermal method to adjust the light response ability,and discussing the performance improvement of the visible light/PMS/ZnFe₂O₄（Vis/PMS/ZFO）system for CIP degradation and the synergistic catalytic mechanism,as well as the adaptability of the system to the water environment,the impact on the ecological environment and the promotion of practical applicationsOptimize the control conditions of hydrothermal preparation to adjust the light response ability of the ZFO.The influencing factors of hydrothermal method were adjusted through single factor experiment.The factors included:p H of precursor solution,hydrothermal reaction temperature and hydrothermal reaction time.The XRD phase structure analysis of the materials under different preparation conditions was carried out to determine the morphology and purity of the prepared crystals.The results showed that the crystallinity of the materials was relatively pure,but under the prepared conditions of p H=12,195℃,10h and p H=12,180℃and 12h,the miscellaneous peak of Fe₃O₄ appeared.Furthermore,the visible light absorption properties were characterized by diffuse reflectance spectroscopy DRS.The result indicated that the band gap width of ZnFe₂O₄ was not affected by the preparation conditions,which maintained at 2.18-2.19 e V.While the separated degree of electron-hole pairs were significantly different.The photocurrent I-t,impedance EIS and Mott-Schottky were used to characterize the separation and transport capacity of photogenerated charges.Finally,the preparation conditions were determined to be p H=12,180℃,14h.Use this material for follow-up research.Discuss the performance improvement of Vis/PMS/ZFO system for CIP degradation and the synergistic catalytic mechanism.The introduction of visible light could achieve100%CIP degradation in 60 min,and the TOC removal was 51.58%in 120 min.Compared with the PMS/ZFO system,the degradation efficiency increased by 20%and the mineralization rate increased by 36.58%.Through the identification of reactive oxygen species,it was found that·OH and ¹O₂ played a major role,and the contribution rate were 65.49%and 22.39%,respectively.Moreover,the·OH concentration under the light system was about 1.6 times in contrast to that in the dark state.Combining the XPS,FTIR analysis of the ZFO surface and the in-situ characterization of the Tafel curve,the performance improvement is mainly due to that the visible light could stimulate the ZFO to generate photo-generated electron-hole pairs,which accelerated the cycle of Zn²⁺-Zn³⁺-Zn²⁺and achieved an increase of the concentration·OH.The transition of oxygen in ZFO is the main source of ¹O₂.The introduction of visible light not only accelerates the conversion of lattice oxygen to active oxygen,but also makes the effective use of dissolved oxygen and increases the generation of ¹O₂.Discuss the adaptability of the research system to the water environment,its impact on the ecological environment and its practical application and promotion.The system has a certain tolerance to different p H,following the order of p H=9>p H=11>p H=7>p H=5>p H=3.Deeply,the degradation performance was significantly improved under alkaline conditions.The p H of solution mainly affected the hydrolyzed form of PMS,CIP and the charged surface properties of ZFO.Among the effects of anions,Cl^-,HCO₃^-,NO₃^-,and H₂PO₄^-have different influences.High concentrations of Cl^-and HCO₃^-showed an obvious"promotion"effects.To be exact,Cl^-might react with CIP and form chlorine by-products,which affected the detection in the experiments.The influence mechanism of HCO₃^-was more complex.Because HCO₃^-not only affected the p H of the water body,but also CIP as an electron-rich body could react with CO₃^-·.Under acidic conditions,NO₃^-could enhance the ability to absorb visible light and thus promoted the photocatalytic reaction.While H₂PO₄^-would compete with PMS for hydroxyl active sites,and at the same time quench free radicals to inhibit degradation.The natural organic matter humic acid has a slight effect on the degradation.Through the analysis of the products,it is found that the attack site of CIP is mainly on the piperazine group,and there is also a certain deoxygenation effect on the quinolone group.The mung bean germination test was used to detect the toxicity of the treated water.The result indicated that the toxicity of treated water decreased by 45%compared with the raw water.Using the effluent from the cloth filter of the Lijiatuo Wastewater Treatment Plant on May as a solvent to test the degradation performance,the performance was almost the same as the ultrapure water.This study is expected to realize practical applications in the field of wastewater treatment.