Synthesis,Characterizations And Photo-fenton Sulfonamide Antibiotics Degradation Performance Of MOF-Derived Fe₃S₄

Sulfonamide antibiotics（SAs）are still widely used as the first broad-spectrum antibiotics used in clinical practice.Among them,sulfamethoxazole（SMX）and sulfisoxazole（SIM）are common human antibiotics,while sulfadiazine（SDZ）is a commonly used veterinary antibiotic.SAs can be discharged into water bodies through several routes,resulting in SAs concentrations in water ranging between ng/L andμg/L.Therefore,it is necessary to remove SAs from wastewater before discharge to natural water bodies.Non-homogeneous photofenton technology,due to its high efficiency,low iron sludge and good reusability,has been widely used for the removal of refractory organic pollutants.However,the photo-Fenton catalysts are difficult to be recycled from the reaction system.MOFs are metal-organic skeletons constructed by metal nodes and organic ligands,which have the advantages of ultra-high specific surface area,diverse structures,tunable morphology and abundant active sites.In this work,MIL-100（Fe）sulfide was derived from magnetic Fe₃S₄,while retaining part of the advantages of its MOF precursor and Fe₃S₄.The derived material Fe₃S₄ is easily recyclable as an excellent narrow bandgap ferromagnetic semiconductor after the reaction,and the abundant reduction sites on the surface can activate H₂O₂ to produce·OH for degradation of organic pollutants.From these aspects,photo-Fenton with Fe₃S₄ as catalyst may have great potential for development.The main work of this thesis is as follows.（1）The magnetic Fe₃S₄ was prepared by hydrothermal synthesis of MIL-100（Fe）and derivatization of MIL-100（Fe）using thioacetamide sulfide.The successful preparation of the material was demonstrated by powder X-ray diffraction characterization.The method of derivatizing Fe₃S₄ using MOF as a template has several advantages over other conventional methods in the literature:Firstly,MIL-100（Fe）is easy to prepare and does not require high sulfidation conditions,so it is relatively convenient to derive high-quality Fe₃S₄.Secondly,since MIL-100（Fe）is used as a template,the synthesized Fe₃S₄ can inherit the advantages of MIL-100（Fe）,so that Fe₃S₄ has a relatively large specific surface area.Meanwhile,many active sites were exposed in the process of derivatization of Fe₃S₄.（2）The precursor MIL-100（Fe）and the derived metal sulfide Fe₃S₄ were characterized by scanning electron microscope,transmission electron microscope,high power transmission electron microscope,magnetic hysteresis loop,ultraviolet-visible diffuse reflectance spectroscopy,electrochemistry and X-ray photoelectron spectroscopy.It was demonstrated that MIL-100（Fe）successfully derived magnetic Fe₃S₄.The morphology of Fe₃S₄ prepared by derivatization was regular flower-like microspheres with good magnetic properties that could be easily separated and recovered from aqueous solution.In addition,Fe₃S₄ has excellent light absorption performance and can utilize both UV and visible light,so that different light sources can be selected in the future according to the actual environment.（3）Testing the performance of derivative Fe₃S₄ photo-Fenton for SMX degradation under light conditions.Efficient degradation of mixed sulfonamide antibiotics was achieved by photo-Fenton under visible light.In this paper,environmental factors affecting SMX degradation,recyclability of materials,SMX degradation mechanism and possible degradation pathways were systematically investigated.The results show that the Fe₃S₄/H₂O₂/vis system can degrade 100%of SMX within 10 min.Also,given the excellent photo responsiveness of Fe₃S₄,it can efficiently degrade SMX from UV to visible light and from real sunlight to light sources of different wavelengths.In this work,the detailed exploration of p H,catalyst dosage,H₂O₂ concentration and inorganic anion.The effects of p H,catalyst dosage,H₂O₂ concentration and inorganic anion on the degradation performance,cycling performance in aqueous solution and performance under real sunlight and different wavelength light sources were explored in detail in this work.The main reactive oxygen species（ROS）in the Fe₃S₄/H₂O₂/vis system were inferred to be·OH and ¹O₂ by capture experiments and electron spin resonance spectroscopy characterization techniques.X-ray photoelectron spectroscopy,instantaneous photocurrent,and impedance spectroscopy were also used to study the photo-Fenton reaction mechanism.Based on UHPLC-MS analysis,the degradation pathways of SMX,SIM and SDZ were proposed.