Ultrafast oxidation of emerging contaminants by novel VUV/Fe2+/PS process at wide pH range: Performance and mechanism

Vacuum UV (VUV) has become a powerful tool for light-assisted advanced oxidation processes because it efficiently dissociates water to produce reactive oxygen species in situ. Heretofore, the performance and synergistic mechanism for emerging contaminants (ECs) removal by VUV/Fe2+/PS have not been reported. Compared with its sub-processes, integrated VUV/Fe2+/PS process can significantly accelerate the degradation and mineralization of three ECs. The synergistic factors of degradation of norfloxacin (NOR), sulfadiazine and tetracycline in VUV/Fe2+/PS process were 1.52, 1.62 and 2.70, respectively. The influence mechanisms of process parameters (PS and Fe2+ dose, initial pH) on the performance of VUV/Fe2+/PS were elaborated, and VUV/Fe2+/PS process can effectively remove NOR at wide pH range (3–10). Combining radical quenching experiments and characteristic substance capture experiments, hydroxyl radical (HO•), sulfate radical (SO4•-), singlet oxygen (1O2), and Fe(IV) were identified as main radical and non-radical species in VUV/Fe2+/PS process. The radical species dominated by HO• and SO4•- contributed more to the degradation of three ECs by VUV/Fe2+/PS (over 60%), and the non-radical species dominated by Fe(IV) and 1O2 also played an important role in ECs removal. Degradation by-products and pathways of NOR by VUV/Fe2+/PS were also investigated. Moreover, synergistic reaction pathways in VUV/Fe2+/PS process were proposed. Effects of water matrices on the performance of VUV/Fe2+/PS were also studied. The secondary wastewater was considered an ideal application scenario for VUV/Fe2+/PS process. All results clearly indicate that VUV/Fe2+/PS is a promising process for ECs removal.