Degradation Properties And Mechanism Of Potassium Ferrate On Typical Fluoroquinolones

Residues of pharmaceutical and personal care products（PPCPs）in the environment,including fluoroquinolone antibiotics（FQs）,are characterized by low concentrations,diversity and unique chemical properties,and are widely present in surface water,groundwater and soil,adversely affecting human health and ecosystems.The removal of FQs by conventional biochemical treatment is inefficient and has a long process.Advanced oxidation or chemical oxidation can achieve its efficient degradation.Among them,ferrate（Fe（Ⅵ））is a kind of green environmental protection agent with disinfection,coagulation,oxidation and other functions,which can effectively remove trace or trace pollutants in water,and has great potential in the field of water treatment.In this study,three typical fluoroquinolones（FQs）:ofloxacin（OFL）,gatifloxacin（GAT）and fleroxacin（FLE）were selected as the research objects.The degradation mechanism of typical fluoroquinolones by ferrate was studied by HPLC,free radical masking experiment and UPLC-QTOF-MS.The optimal reaction conditions of Fe（Ⅵ）oxidation degradation of OFL,GAT and FLE were determined.The reaction kinetics model was established to investigate the effects of different coexisting substances on the oxidation effect,and the reaction path was speculated by identifying the intermediate products.To clarify the reaction mechanism of Fe（Ⅵ）oxidation degradation of three FQs,improve the theory of Fe（Ⅵ）oxidation FQs,provide reference for the treatment of wastewater containing trace antibiotics,and provide theoretical and technical support for the pollution control of PPCPs in water.The main conclusions are as follows:（1）The degradation efficiency of OFL reached 92.38%after 30 minutes of oxidation,with the molar ratio of Fe（Ⅵ）to OFL of 40:1,pH of 8 and temperature of 25℃.In the first 5minutes rapid reaction stage,OFL degradation conformed to pseudo second-order reaction kinetics.The ring cleavages of quinolone,piperazine and oxazine rings of OFL were achieved by decarboxylation,demethylation,decarbonylation and hydroxylation.（2）The degradation efficiency of GAT reached 93.48%after 30 minutes of oxidation,with the molar ratio of Fe（Ⅵ）to GAT of 30:1,pH of 8 and temperature of 25℃.In the first15 minutes rapid reaction stage,GAT degradation conformed to pseudo second-order reaction kinetics.The ring cleavages of quinolone,piperazine rings and the removal of cyclopropyl group on the main body of GAT were achieved by decarboxylation,decarbonylation,decarbonylation and hydroxylation.（3）The degradation efficiency of FLE reached 95.80%after 30 minutes of oxidation,with the molar ratio of Fe（Ⅵ）to FLE of 20:1,pH of 8 and temperature of 25℃.In the first 15minutes rapid reaction stage,GAT degradation conformed to pseudo second-order reaction kinetics.The ring cleavages of quinolone and piperazine rings of FLE were achieved by decarboxylation,decalkyl,decarbonylation,hydroxylation and defluorination.（4）In the oxidation process of OFL,GAT and FLE with ferrate,Fe（Ⅵ）and intermediate high valence iron play a major role,and the contribution rate of hydroxyl radicals and other active substances generated during the reaction is relatively low.Various coexisting substances had different effects on the degradation of three FQs.Cl^-、NO₃^-、SO₄^2-and HCO₃^-had little effect on the degradation effect.Mg²⁺、Ca²⁺and Cu²⁺had a slight inhibitory effect on the degradation effect.Humic acid had a significant inhibitory effect on the degradation of three FQs.