Efficiency And Mechanism Of Tetracycline Catalytic Degradation By Multimetallic Photo-Fenton Based On Ferrihydrite

In today’s society,medical technology and the pharmaceutical industry are developing rapidly,and various drugs are widely used in all walks of life.The environmental problems caused by this have also attracted people’s attention.Among them,the spectral antibiotics represented by Tetracyclines（TCs）have been widely used for a long time,which has caused a large amount of them to flow into nature and endanger human life and health.Ferrihydrite（Fh）is a typical nano mineral widely distributed on the surface.It has the characteristics of small particles,large specific surface area,and strong reactive sites and is a natural adsorbent and catalyst.CuO nanoparticles（CuO-NPs）has also been widely studied in the field of photocatalysis due to its good photocatalytic activity,wide sources,non-toxicity and harmlessness.Therefore,this article is based on two substances,Fh and CuO-NPs,under photo-Fenton conditions,to catalytically degrade TCs.The Fh and CuO-NPs were prepared in the laboratory,and the prepared Fh and CuO-NPs were characterized by SEM,EDS,XRD,BET and other characterization methods.The two solids were mixed in different proportions to obtain four catalysts:Fh,3%CuO-NPs-doped Fh,6%CuO-NPs-doped Fh,and 9%CuO-NPs-doped Fh,and the adsorption performance was explored.It was found that the adsorption performance of the four catalysts is 81.91%,79.01%,75.01%,and 70.18%,respectively,for about 24 hours of static adsorption.The adsorption reaction process was fitted with adsorption kinetics and adsorption isotherms,and the adsorption reactions of the four catalysts to TCs conformed to the second-order kinetic equation and Langmuir isotherm model,and the adsorption constants R_L of the four catalysts were all less than 1.It shows that the catalyst has good adsorption effect on TCs.Under dark-Fenton and photo-Fenton conditions,the influence factors such as light,reaction time,pH value,catalyst dosage,H₂O₂ concentration,and initial concentration of tetracycline are explored,and the optimal Chemical kinetic analysis was performed under optimal reaoction conditions.Under dark-Fenton,6%CuO-NPs-doped Fh was selected as the catalyst to remove TCs in the solution,and the removal rate could reach 94.06%at 60min,which the reaction process conforms to the first-order reaction kinetics.Keeping the reaction conditions unchanged,select 6%CuO-NPs doped Fh to remove TCs in the solution under the photo-Fenton condition,and the removal rate reached 77.65%at 15 min and 99.20%at 60 min,which the reaction process conforms to the second-order reaction kinetics.The degradation products of TCs degraded under the two conditions of dark Fenton and photo Fenton were detected by the combined method of ultraviolet full-wavelength scanning and LC-MS,and the degradation path of TCs under the two conditions was obtained.Studies have found that the degradation of TCs is more thorough under the conditions of photo-Fenton,while the dark Fenton reaction will generate a more stable substance,and the degradation of TCs is not complete enough.