The Research On The Removal Of Norfloxacin From Water Via The Activation Of Persulfate With Fe/N Co-Doped Graphene Oxides

In recent decades,the problem of antibiotic residues in aquatic environment has been widely concerned because of mass antibiotics used and the incomplete metabolic transformation in organisms.Norfloxacin（NFX）is a fluoroquinolone antibiotic that is widely used due to its high activity against gram-negative and gram-positive bacteria.But NFX is not easily degraded naturally and even trace amounts of NFX can adversely affect the water environment and human health.Persulfate-based advanced oxidation processes（SR-AOPs）have come into wide use in the removal of refractory pollutants based on their selective degradation in harsh environments.The treatment effect of SR-AOPs is closely related to the activation methods of persulfate and the catalysts used.Therefore,it is of great significance to research new heterogeneous catalysts for the practical application of SR-AOP_S.In this study,the Fe and N co-doped graphene（FeNGO）was synthesized by simple impregnation and pyrolysis method using GO,urea and iron salt as raw materials.FeNGO was used to activate peroxomosulfate（PMS）for NFX degradation.A series of characterization analyses showed that FeNGO had a two-dimensional porous sheet structure,abundant nitrogen species and active sites,and a high degree of graphitization.NFX degradation experiments showed that FeNGO showed excellent catalytic degradation performance for NFX,and 97.7%of NFX could be removed within 30 min.The reaction rate constant by FeNGO was 7.1 times and 1.7 times of nitrogen-doped graphene（NGO）and iron-doped graphene（Fe GO）,respectively.XPS analysis and active sites masking experiments indicated that Fe₃N was the main active sites of FeNGO.The results of electron spin resonance（ESR）and radical quenching experiments demonstrated that both radical process(SO₄^·-,·OH and O₂^·-)and non-radical process（¹O₂）were involved in the NFX degradation,but O₂^·-and ¹O₂ played major roles.In the reaction process,¹O₂ was generated from O₂^·-transformation and PMS decomposition,and dissolved oxygen did no contribution to the production of ¹O₂.According to the Fukui function calculation,the pyridine portion of quinoline ring is more vulnerable to O₂^·-attack,while C-F bond,piperazine ring and the benzene portion of quinoline ring are more vulnerable to ¹O₂ attack.The possible degradation pathways of NFX were proposed based on a total of 15 intermediates identified by LC/MS analysis.Defluorination,decarboxylation,deethylation,piperazine ring opening and quinoline ring opening were considered as the main degradation mechanism in this study.FeNGO has strong p H adaptability,showing good catalytic activity in solution p H range from 3 to 9.The removal of NFX by FeNGO was slightly affected in saliferous water matrices,which might be due to the influence of anions on the radical process,but 80%NFX degradation efficiency could still be achieved.It is hoped that this study will create values for the practical application of coexistence of free radical and non-free radical catalytic systems.