Accelerate sulfamethoxazole degradation and detoxification by persulfate mediated with Fe2+&dithionite: Experiments and DFT calculation

Advanced oxidation process (AOPs) is one of the most effective technologies for organic pollutants removal. In this study, diverse reactive species generation and enhanced sulfamethoxazole (SMX) degradation were investigated based on persulfate (PDS) activated by Fe2+&dithionite (DTN). When involving Fe2+&dithionite in PDS, SMX degradation efficiency reached 84 % within 30 min following a pseudo-first-order kinetic, which was higher than those in Fe2+/PDS (50.4 %) and Fe2+/O2/DTN (41.3 %). SO4•- and •OH were identified as dominant reactive species with a crucial role of FeSO3+ based on quenching experiment and electron spin resonance (ESR). The contributions of SO4·-, ·OH, and other species to SMX degradation were 60.1 %, 33.9 %, and 6 %, respectively. In Fe2+/DTN/PDS system, SMX was effectively degraded under nearly neutral pH (5.0-9.0), with activation energy of 96.04 kJ·mol-1. The experiments and density functional theory (DFT) calculation demonstrated that three functional groups (benzenesulfonamido, benzene ring, and oxazole ring) were attacked for SMX degradation. Moreover, acute toxicity to Vibrio fischeri has enhanced in the earlier degradation process due to the intermediates and weaken with the continuous reaction. This work not only provides a high-activity SO4·--AOP for refractory pollutant treatment with possible dual radical generation resources, but elucidated diverse reactive species formation with Fe2+&dithionite.