Vacuum ultraviolet light-driven, FeOCl-catalyzed heterogeneous photo-Fenton process for enhanced degradation of acetaminophen in water: Efficacy and mechanism.

Vacuum ultraviolet (VUV) light has witnessed promising application potential in water treatment for the in situ generation of a series reactive species. Therefore, the coupling of VUV with heterogeneous Fenton systems offers the potential to enhance catalytic activity and pollutant degradation efficiency. Herein, a novel VUV/H2O2/FeOCl system, featuring VUV irradiation and FeOCl as the catalyst, was developed for acetaminophen (APAP) degradation. The as-prepared FeOCl was systematically characterized by XRD, XPS and SEM. The VUV/H2O2/FeOCl system exhibited significant superiority when compared to single systems (VUV, H2O2, FeOCl) and binary combinations (VUV/H2O2, VUV/FeOCl, H2O2/FeOCl). Specifically, the pseudo-first-order rate constant for APAP degradation in the VUV/H2O2/FeOCl process was 5.1-366.9 times higher than other processes, with corresponding mineralization rates enhanced by 7.4 %-81.1 %. Electron paramagnetic resonance (EPR) analysis and radical quenching experiments confirmed the involvement of singlet oxygen (1O2), holes (h+), hydroxyl radicals (•OH), electrons (e-), and superoxide radicals (O2•-) in the VUV/H2O2/FeOCl system. The generation of •OH was further validated via fluorescence spectroscopy, which revealed that the VUV/H2O2/FeOCl system achieved optimal H2O2 activation and highest •OH accumulation. The degradation pathway of APAP was systematically proposed based on an ultra-performance liquid chromatography system coupled with triple quadrupole mass spectrometer (UPLC-QqQ-MS) analysis, and the evolution of intermediates toxicity was also investigated. Moreover, the VUV/H2O2/FeOCl system demonstrated excellent stability and reusability, enabling efficient degradation of various aquatic pollutants. This highly efficient process provides new insights into the remediation of pharmaceutical-contaminated water.