title: Sulfate radical-based oxidation of fluoroquinolone antibiotics: Kinetics, mechanisms and effects of natural water matrices.
abstract: Widespread occurrence of fluoroquinolone antibiotics (FQs) in surface water, groundwater, soil and sediment has been reported and their remediation is essentially needed. Sulfate radical (SO4-) based advanced oxidation processes (SR-AOPs) are promising technologies for soil and groundwater remediation. In this study, the degradation kinetics, mechanisms, and effects of natural water matrices on heat-activated persulfate (PS) oxidation of FQs were systematically investigated. Experimental results clearly demonstrated that 92% of CIP was removed within 180 min (pH = 7, 60 °C). Higher temperature and lower pH facilitated the degradation of ciprofloxacin (CIP). The piperazine moiety of CIP was identified as the reactive site for SO4-attack by comparison with substructural analogs, flumequine (FLU) and 1-(2-fluorophenyl) piperazine (FPP). A comparison of the degradation of CIP, norfloxacin (NOR), enrofloxacin (ENR) and ofloxacin (OFL) confirmed that the presence of cyclopropane ring also influence the degradation of FQs. Water matrix significantly influenced the degradation of CIP and ENR, and the degradation rate followed the order of Milli-Q water (pH = 7) > groundwater > artificial seawater > artificial surface water > lake water. Degradation products of CIP in different water matrix were enriched by solid phase extraction (SPE) and then analyzed by liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (LC-ESI-MS/MS). Detailed transformation pathways of CIP were proposed and were compared with respect to different water matrices. Four transformation pathways including stepwise piperazine ring oxidation, OH/F substitution, hydroxylation, and cyclopropane ring cleavage were proposed for CIP degradation. Results clearly show that the water matrix influenced the degradation of FQs appreciably, a phenomenon that should be taken into consideration when applying SR-AOPs for remediation of soil and groundwater contaminated by FQs.
authors: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China.
authors: Canlan
authors: C
authors: Jiang
authors: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China.
authors: Yuefei
authors: Y
authors: Ji
authors: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China.
authors: Yuanyuan
authors: Y
authors: Shi
authors: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China.
authors: Jifei
authors: J
authors: Chen
authors: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China. Electronic address: ctm@njau.edu.cn.
authors: Tianming
authors: T
authors: Cai
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D002939:Ciprofloxacin; D024841:Fluoroquinolones / Q000737:chemistry; D007700:Kinetics; D053719:Tandem Mass Spectrometry; D014867:Water; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D014874:Water Pollutants, Chemical; D014867:Water; D002939:Ciprofloxacin
keywords: Ciprofloxacin; Fluoroquinolone antibiotics; Sulfate radical; Transformation mechanisms; Water matrix