Study On The Synthesis Of Co/TiO₂@CNFs And Their Activation Of PMS For Catalytic Degradation Of Typical Antibiotics

In recent years,antibiotics,as emerging organic pollutants,have appeared in the natural water environment and have become a widespread concern of many scholars at home and abroad,which pose a potential long-term threat to aquatic organisms and human health.Sulfamethoxazole（SMX）is a sulfamethoxazole antibiotic widely used in human and veterinary medicine.Coumarin（COU）is a coumarin antibiotic used in anti-tumor,antibacterial（Escherichia coli）,anticoagulation and insecticidal（housefly larvae）.As these two antibiotics are used in large quantities and have hidden safety risks in the aquatic environment,it is of great significance to develop effective treatment methods to remove them for human health and water environment safety.Cobalt-carrying catalysts have been widely used in advanced oxidation technology based on sulfate radical（SR-AOPS）.In this study,carbon nanofiber membranes（Co@CNFs）and carbon nanofiber membranes（Co/Ti O₂@CNFs）supported with cobalt single metal nanoparticles were prepared by electrostatic spinning and heat treatment techniques,and the adsorption and catalytic properties of the prepared materials were tested to optimize the material composition allocation ratio.Scanning electron microscopy（SEM）,Transmission electron microscopy（TEM）,High-resolution transmission electron microscopy（HRTEM）,High angle annular dark-field scanning transmission electron microscopy（HAADF-STEM）,Element mapping,X-ray diffraction（XRD）,Raman spectroscopy,Thermos-gravimetric analysis（TGA）,Fourier Transform infrared spectroscopy（FTIR）,nitrogen adsorption and desorption,X-ray photoelectron spectroscopy（XPS）,nanometer particle size potentiometer（Zeta potential）and a series of methods were used to characterize the physical and chemical properties of the batch prepared materials.SMX and COU were used as target pollutants to test the adsorption catalytic performance of the two materials.The results showed that2Co@CNFs had the best adsorption catalytic effect.XCo/Ti O₂@CNFs composite catalyst was prepared by adding Ti O₂with different contents based on the 2Co@CNFs formula,where the X represents the weight fraction of titanium（material added value）.Further adsorption catalytic degradation experiments showed that 1Co/Ti O₂@CNFs had the best catalytic degradation effect on SMX and COU antibiotics.Combined with the analysis and characterization results,1Co/Ti O₂@CNFs have the largest specific surface area and total pore volume,the largest graphitization degree,crystal irregularity,and the most defects.Taking SMX as a typical pollutant,1Co/Ti O₂@CNFs（Co/Ti O₂@CNFs for short）was selected to catalyze the degradation of typical antibiotics by PMS to study the influencing factors.The effects of different factors（pollutant concentration,PMS dose,p H,catalyst dosage,water temperature,coexisting ions,etc.）and material calcination temperature on the degradation performance of SMX in Co/Ti O₂@CNFs activated PMS system were investigated.At the same time,to test the reusability and stability of the material,the cyclic degradation experiment and the catalyst characterization analysis were carried out before and after the degradation reaction.The results showed that under the conditions of[SMX]=40μmol·L^-1,[PMS]=1 mmol·L^-1,reaction temperature 25℃,a dosage of 0.1 g·L^-1,p H 5.8,the degradation rate of SMX reached 98.8%at 30min,and almost completely removed in 40min.The degradation rates of SMX by Co/Ti O₂@CNFs activated PMS system is≥99%,99%,93%,91%and 89%in 5 cycles,indicating that the material has good reusability.XRD analysis of Co/Ti O₂@CNFs material before and after the catalytic reaction shows that the lattice structure of the material remains relatively stable before and after the reaction,which further proves that the material has good stability.Ten intermediates of SMX degradation by Co/Ti O₂@CNFs activated PMS were identified by liquid mass spectrometry（LC-MS）,free radical trapping experiment,ESR and XPS analysis.Four possible transformation pathways of SMX degradation were proposed,and the degradation mechanism of SMX was elucidated.The results showed that four active species SO₄^·-,^·OH,O₂^·-and ¹O₂were produced during the catalytic degradation of SMX,among which ¹O₂played a dominant role.On the surface of electrospinning fibers,the Co（Ⅱ）-Co（Ⅲ）-Co（Ⅱ）REDOX cycle activates PMS to produce SO₄^·-and^·OH,and further converts to O₂^·-and ¹O₂.The four active species jointly promote the degradation of SMX.Ti O₂improves the catalytic efficiency by promoting the formation of the Co—OH complex on the catalyst surface.