Oxidation and detoxification of fluoroquinolones via dual-wavelength ultraviolet (185 nm + 254 nm) excitation of peroxymonosulfate: Critical role of 185 nm photons, toxicity evolution, and environmental adaptation

The widespread use of fluoroquinolones (FQs) has posed serious threats to aquatic ecosystems and human health. Herein, vacuum ultraviolet (VUV), a dual-wavelength ultraviolet (185 nm + 254 nm), exciting peroxymonosulfate (PMS) was used for the first time to oxidize and detoxify FQs. VUV/PMS process showed absolute advantages over its sub-processes in oxidation of three FQs from aspects of degradation rate , mineralization , rate constant, energy consumption and technical cost. VUV/PMS eliminated norfloxacin (NOR) effectively in a wide pH range (3−11). Besides, hydroxyl radical and sulfate radical were assessed as dominating reactive oxygen species through fluorescence probe and radical quenching experiments in VUV/PMS, and they contributed 41.18 % and 26.47 % to NOR degradation with steady-state concentrations of 1.00 × 10 −10 and 1.94 × 10 −10 M separately. Moreover, synergistic mechanism of VUV/PMS was revealed, in which 185 nm photons played a key role. Pathways of NOR decomposition by VUV/PMS included piperazine ring conversion, defluorination , and quinolone ring conversion. Meanwhile, VUV/PMS achieved effective detoxification of NOR. Finally, the effect of water quality factors on the oxidation capacity of VUV/PMS was also surveyed and the practicability of VUV/PMS in three real waters was verified. All results manifested that VUV/PMS process had promising application in FQs removal. • Energy-saving VUV/PMS process achieved fast degradation of FQs with low cost. • SO 4 •- (1.94 × 10 −10 M) and HO • (1.00 × 10 −10 M) were main ROS in VUV/PMS process. • Synergistic mechanisms of VUV/PMS highlighted the key role of 185 nm photons. • Bean sprout culture proved that VUV/PMS achieved efficient NOR detoxification. • VUV/PMS process effectively removed NOR in three practical waters.