Novel VUV/H2O2/PDS process dominated by singlet oxygen for ultrafast degradation of fluoroquinolones in water: Synergistic mechanism and detoxification evaluation

Aquatic fluoroquinolones (FQs) pose escalating ecological risks. The vacuum ultraviolet/hydrogen peroxide (VUV/H 2 O 2 ) process is promising due to its good compatibility with mainstream water treatment processes, but its oxidation capacity is limited. To overcome this bottleneck, this work constructed a novel VUV/H 2 O 2 /peroxydisulfate (PDS) process for the degradation of FQs in water. As a result, the removal efficiency of three typical FQs by VUV/H 2 O 2 /PDS within 4 min reached 98.1%–99.1%, which was significantly higher than that of its sub-processes. Furthermore, reactive oxygen species (ROS) quenching experiments revealed that singlet oxygen ( 1 O 2 ) played a dominant role, with the contribution order of 1 O 2 > the hydroxyl radical>the sulfate radical ( SO 4 • − ) > the superoxide radical. Notably, the addition of PDS primarily enhanced oxidation performance by generating 1 O 2 , rather than SO 4 • − . In addition, degradation pathways of norfloxacin (NOR, a typical FQs) were inferred by density functional theory calculations and mass spectrometry analysis. Theoretical toxicity calculations indicated that VUV/H 2 O 2 /PDS reduced the environmental toxicity of NOR. Mung bean germination experiments further demonstrated its ultrafast detoxification efficiency for NOR, achieving a 96.9% detoxification rate within 20 min. Additionally, the effects of water matrices on NOR removal via VUV/H 2 O 2 /PDS were also explored. Finally, the relatively low cost of VUV/H 2 O 2 /PDS process and its outstanding performance in four actual waters highlighted its high potential for advanced treatment of pharmaceutical wastewater.