Studies On The Catalytic Performance Of Core-Shell CoFe₂O₄/CoFe₂S₄ Catalysts For Heterogeneous Fenton-like System

Berberine is a common antibiotic that inhibits both Gram-positive and Gram-negative bacteria,so it is widely used as a broad-spectrum antibiotic.However,the production or use of berberine results in a large amount of waste water containing residual berberine.If it is directly discharged,it will kill or inhibit beneficial microorganisms in water bodies,soil,and sediments,leading to the destruction of the ecological balance of the environment.Therefore,the removal of such refractory biodegradable pollutants from wastewater has important practical significance and urgency.Traditional physical treatment methods are not ideal for degrading berberine wastewater.As an efficient water treatment technology,chemical methods can rapidly oxidize and completely degrade organic pollutants.Among them,advanced oxidation methods have attracted much attention because they can generate strong oxidizing free radicals.The heterogeneous Fenton reaction system overcomes the problem of strict pH range requirements in the homogeneous system,and it is not easy to produce"iron mud".The key of the heterogeneous Fenton technology lies in the catalytic material.With the in-depth research,it is discovered that the mixed metal catalyst has higher catalytic activity than the single metal catalyst.Therefore,this paper prepares a spinel-type Co/Fe composite sulfide catalyst（CoFe₂O₄/CoFe₂S₄）with a core-shell structure to catalyze PMS and H₂O₂ to oxidatively degrade berberine.Firstly,the CoFe₂O₄/CoFe₂S₄ catalyst was prepared by a simple and gentle two-step hydrothermal method.Through scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,N₂-adsorption desorption curve（BET）,X-ray diffraction（XRD）and X-ray photoelectron Energy spectroscopy（XPS）,the apparent morphology,crystal structure and Characterization of elemental composition.SEM results show that the prepared CoFe₂O₄/CoFe₂S₄ has a uniformly dispersed nanoplatelet and nanoflower particle hybrid morphology;in the CoFe₂O₄/CoFe₂S₄ material,CoFe₂S₄ is at the edge of the CoFe₂O₄nanoplatelet,which is tested by TEM;It can be seen from the BET test results that the specific surface areas of CoFe₂O₄ and CoFe₂O₄/CoFe₂S₄ are 60.58 m²/g and 51.59 m²/g,respectively;XRD results sugggest that CoFe₂O₄ and CoFe₂O₄/CoFe₂S₄ were successfully synthesized;the CoFe₂O₄/CoFe₂S₄ catalyst contains Co²⁺/Co³⁺,Fe²⁺/Fe³⁺,O^2-and S^2-,confirming the successful synthesis of CoFe₂O₄/CoFe₂S₄,which is can be known by XPS.Secondly,a CoFe₂O₄/CoFe₂S₄-PMS system was constructed to oxidatively degrade berberine wastewater.When the berberine sample concentration is 10 mg/L,the dosage of CoFe₂O₄/CoFe₂S₄=1 mg/L,PMS concentration=0.8 mM,temperature=40℃,pH=7,the degradation rate of berberine can reach 98.4%within 60minute;the degradation rate of berberine can still reach more than 90%after using CoFe₂O₄/CoFe₂S₄ catalyst for three times,which proves that the catalytic material has good stability;the removal rate of TOC within 60minutes is 77.8%;EPR shows that SO₄·^-and·OH are the main free radicals in the degradation of berberine.The free radical inhibition experiment confirmed that SO₄·^-was the main free radical for degradation of berberine.The intermediate products and infer the possible degradation pathways of berberine are analyzed by high-performance liquid-mass spectrometry（LC-MS/MS）.Finally,a CoFe₂O₄/CoFe₂S₄-H₂O₂ system was constructed to degrade berberine wastewater.Under the optimum conditions of CoFe₂O₄/CoFe₂S₄=7.5 mg/L,H₂O₂=80 mM,temperature=40℃,and pH=5,the degradation rate of berberine can reach 94.3%within 180min;stability tests show that the degradation rate of berberine can still reach over 89%after three cycles,indicating the good stability of CoFe₂O₄/CoFe₂S₄;EPR test the free radical suppression experiment confirm that the main active oxygen species in degradation process is·OH.Free radical suppression experiments determined that·OH degraded berberine.A simple mechanism exploration was carried out,but the content is not comprehensive enough.