Rapid degradation of norfloxacin by VUV/Fe2+/H2O2 over a wide initial pH: Process parameters, synergistic mechanism, and influencing factors

Vacuum UV (VUV) technology has attracted much attention because it effectively splits water to generate reactive oxygen species (ROS) in situ and has the advantages of UV. So far, the synergistic mechanisms, formation pathways and contributions of ROS in VUV/Fe2+/H2O2 process have not been extensively studied. Herein, complete removal (at 4 min) and 63.3% mineralization (at 8 min) of 45 μM norfloxacin (NOR) were achieved at neutral pH by VUV/Fe2+/H2O2 (90 μM Fe2+ and 3 mM H2O2). Compared with its subsystems, VUV/Fe2+/H2O2 can not only increase the pseudo-first-order reaction rate constant of NOR removal by 2.3–14.9 times and increase the mineralization by 20.4−59.4%, but also reduce the residual ratio of H2O2 by 19.9−70.1% and reduce total cost by 20.0−68.0%. The synergy factor of VUV/Fe2+/H2O2 was 3.97, which was attributed to the VUV irradiation promoting iron redox cycle and H2O2 decomposition. Moreover, hydroxyl radical and superoxide radical, which were identified as the main ROS, contributed 79.07% and 18.47% to NOR removal, respectively. Degradation pathways of NOR were proposed. Furthermore, effects of coexisting ions and dissolved organic matter were investigated. As an energy-saving and efficient process, the satisfactory results of VUV/Fe2+/H2O2 applied in real waters also highlight its application potential.