Study On The Removal Efficiency And Mechanism Of Fluoroquinolone Antibiotics In Nanosized Zero-valent Copper Based Fenton-like Systems

Fluoroquinolones?FQs?are emerging organic compounds,which are present in the aquatic environment with trace concentrations and pose a potential threat to human health.In this study,an environmentally friendly nanoscale zero-valent copper?nZVC?was used as catalyst to deactivate antibiotics in water by a Fenton-like system.The degradation behavior and mechanism of NOR and CIP in heat/nZVC/PS and Air/nZVC/AA processes were systematically investigated.nZVC was characterized by TEM,BET,XRD and Zeta potential test.The results showed that the specific surface area of nZVC was 9.268 m²/g,the total pore volume was 0.029 cm³/g,the total pore diameter was 14.255nm,and the isoelectric point was 6.7.In heat-enhanced nZVC/PS system,appropriately increasing the reaction temperature?40?C?could significantly enhance the removal efficiency of NOR.In order to explore the catalytic performance of nZVC,the removal efficiencies of target pollutants in various systems with nZVC,mZVC and Cu²⁺as PS activators were compared.The results showed that no matter under 25?C condition or 40?C condition,nZVC showed the efficient catalytic performance.Almost complete removal of NOR was achieved at 5 min when the operating conditions were set at 0.05 g/L nZVC and 1 mM PS with 40?C.According to the effect of NCP on the removal efficiency and the determination of Cu⁺released concentrations,it could speculate that Cu⁺was the copper active species to activate PS.In addition,the Cu²⁺was continuously reduced to Cu⁺by Cu⁰ and O₂^-?in the reaction process.The dynamic balance of Cu⁺/Cu²⁺was an fundamental cause of the continuous generation of active free radicals in the system.Through the radical quenching experiments,SO₄^-?and?OH were identified as the dominant reactive free radicals in the nZVC-based Fenton-like system.Besides,the results showed that the removal efficiency of NOR increased with the increase of PS concentration and reaction temperature and decreased with the increase of NOR initial concentration.With the increase of the dosage of nZVC,the removal efficiency of NOR appeared to increase first and then decrease and the highest removal efficiency occured at the dosage of 0.1 g/L.Due to the acid corrosion,the removal effect was most significant at pH 3.0.Finally,eight degradation products were identified,and four possible degradation pathways were proposed by UPLC-MS/MS analysis.It was also speculated that the cleavage of piperazine ring was the main degradation pathway.The use of nZVC to catalyze AA was a green and economical water treatment method.In nZVC/AA/Air system,Cu⁺and AA generated a series of reactions to produce H₂O₂.Then H₂O₂ and Cu⁺further produced?OH by Fenton-like system,which allowed CIP to degrade.When nZVC dosage was 0.1 g/L,AA concentration was 1 mM,and reaction temperature was 25?C,the removal efficiency of CIP after 1 h was as high as 85.1%.In the range of experimental research factors,the CIP removal decreased with the increase of chloride ion concentration.In the case of increasing nZVC dosage and AA concentration,the CIP degradation firstly increased and then decreased.The catalytic mechanism showed that?OH was the dominant free radical in the nZVC/AA/Air system.And the cyclic reaction of Cu⁺/Cu²⁺and Cu?I??AA?_x/Cu?II??AA?_y provided a continuous catalytic capability for the degradation of organic pollutants.