Preparation Of Supported Porous Fe₃O₄ And Its Ultrasonic-Fenton Degradation Performance Of Tetracycline

Tetracycline wastewater can cause serious harm to human health and ecological environment.At present,the technologies for degrading tetracycline wastewater include physical-chemical methods,biological methods,advanced oxidation technologies,etc.,but the first two technologies are affected by the treatment cost and treatment effect.Among the advanced oxidation technologies,the Fenton method has high cost and ultrasonic technology consumes a lot of power and other factors.Therefore,the ultrasonic-Fenton method combining two advanced oxidation technologies has become an efficient method for the treatment of tetracycline wastewater.In this paper,two kinds of catalysts,Fe₃O₄/activated carbon and Fe₃O₄/foamed carbon,were synthesized by using an improved solvothermal method to support nano-Fe₃O₄on activated carbon and carbon foam respectively,and they were used to degrade tetracycline in ultrasonic-Fenton system.The two materials were characterized by XRD,SEM,TEM,VSM and other techniques,the morphology and physicochemical properties of the materials were analyzed,the degradation rate of tetracycline under different conditions was explored,the stability and reuse properties of the materials were investigated,and the mechanism of the degradation reaction was explored.Both Fe₃O₄/activated carbon and Fe₃O₄/foamed carbon well inherit the pore structure of activated carbon and foamed carbon.Fe₃O₄was uniformly loaded on the surface and in the pores of the material,with an average size of about 200nm,good crystallinity,and polycrystalline structure.Fe₃O₄/carbon foam has a larger pore structure than Fe₃O₄/activated carbon,and these pore channels are interconnected to form a three-dimensional porous structure.The degradation efficiency of tetracycline in different systems was ultrasonic-Fenton（Fe₃O₄/foamed carbon）>ultrasonic-Fenton（Fe₃O₄/activated carbon）>ultrasonic-Fenton（pure Fe₃O₄）>Fenton alone>ultrasonic alone.The optimal experimental conditions for the degradation reaction are:the initial concentration of tetracycline is 50mg/L,pH=3,temperature is 25℃,H₂O₂ dosage is 3mmol,ultrasonic power is 250W,catalyst dosage（Fe3O4/foamed carbon is 0.15g）,Fe3O4/activated carbon is 0.18g).Both catalysts have good stability and reuse properties.The degradation rate of Fe₃O₄/carbon foam to tetracycline can reach 98%in30min,and the degradation rate of Fe₃O₄/activated carbon can reach 92%in 40min.This is due to the unique three-dimensional macroporous structure of carbon foam,which can provide more active sites point.The unique pore structure of the carrier can make Fe₃O₄more dispersed,the large pore is more conducive to the diffusion of ultrasonic waves,and at the same time,the ultrasonic residence time is longer,the utilization rate of ultrasonic waves is improved,and a microreactor can be formed on the surface of the carrier,thereby improving the degradation efficiency.The mechanism of the degradation reaction showed that ultrasound and Fenton’s reagent had a good synergistic effect.Ultrasound promoted the conversion of substances in the intermediate process of Fenton reaction,and the degradation of tetracycline was dominated by·OH.