Study On The Degradation Of Tetracycline By Activating Permonosulfate On Bentonite With CuFe₂O₄

Tetracycline（TC）is widely used in animal husbandry and medical care industry.However,after the wastewater reaches the relevant discharge standards,there will still be a certain concentration of TC,which will continue to accumulate in the water environment and soil,causing pollution to the environment.Therefore,the efficient degradation of TC is the key to solving the problem of antibiotic pollution.In recent years,advanced oxidation technology based on peroxymonosulfate（PMS）has been applied in the treatment of tetracycline wastewater,and the preparation of green and efficient catalysts is a research hotspot to improve catalytic efficiency.The ferric cuprite CuFe₂O₄is cheap and easy to obtain,but it is magnetic and prone to agglomeration.Bentonite（Bent）as a carrier can not only improve its dispersibility,but also enhance its catalytic activity by utilizing the synergistic effect of bimetals.In this paper,bentonite-supported CuFe₂O₄was prepared by co-precipitation method.X-ray diffraction（XRD）,scanning electron microscopy（SEM）,Fourier transform infrared spectroscopy（FT-IR）and specific surface area（BET）characterization showed that CuFe₂O₄particles were loaded on the surface of Bent.CuFe₂O₄@Bent-400 was successfully prepared.After loading,the specific surface area and pore volume of the composite increased,the average pore size decreased slightly,and the material belonged to the mesoporous structure.The effects of catalyst dosage,PMS dosage,initial pH and temperature on the degradation rate of TC were investigated.The degradation rate of TC showed a trend of increasing first and then decreasing with the dosage of catalyst and PMS.The initial pH in the range of 2-10 had no obvious effect on the system.The dosage of catalyst was 0.20g/L and the dosage of PMS was 0.40g/L,when the initial pH was 6.0,the degradation rate of TC reached 96.2%.The apparent activation energy of the reaction was calculated to be 27.15 k J/mol through the effect of the reaction rate on the temperature.Through the response surface method,a mathematical model of the TC degradation rate on the catalyst dosage,PMS dosage and initial pH was established,and the interaction between the three factors was explored.The reacted catalyst was recovered and used for repeatability tests.The results showed that after 6times of recycling,the degradation rate of TC decreased by less than 5%,the dissolution concentration of ions in water was also small,and the catalyst had good stability.In addition,the effects of common inorganic anions（HCO₃^-,Cl^-,NO₃^-,H₂PO₄^-）and natural organic matter（HA）in natural water environment on TC were explored,and they all inhibited the degradation of TC,among which H₂PO₄^-inhibited the degradation of TC.The effect is the most obvious,and the influence of NO₃^-is the least.On this basis,the reaction mechanism and degradation pathway of TC degradation by CuFe₂O₄@Bent-400/PMS system were discussed.Quenching experiments and electron paramagnetic resonance（ESR）results show that the active species produced by this system are·OH,SO₄^-·and ¹O₂,of which·OH contributes the most.Through X-ray photoelectron spectroscopy（XPS）analysis,the existence forms and proportions of Fe,Cu,and O changed before and after the reaction.Combined with the identification of active substances,the reaction mechanism was inferred.Fe³⁺/Fe²⁺and Cu²⁺/Cu⁺cycle is the promotion of SO₄^-·and·OH is one of the sources of production.The results of ultraviolet-visible absorption spectroscopy（UV-Vis）,three-dimensional fluorescence（3D-EEM）and total organic carbon（TOC）analysis showed that TC was converted from macromolecular substances to small molecular substances during the degradation process,and part of it was mineralized to CO₂and H₂O.Finally,13 major intermediates were detected by liquid chromatography-mass spectrometry（LC-MS）,and 3 possible degradation pathways were proposed based on these products.