Degradation of sulfanilamide in aqueous solution by ionizing radiation: Performance and mechanism

Sulfonamide (SA) is an emerging contaminants and the efficient treatment of SA containing wastewater remains a challenge. Herein, SA degradation by gamma irradiation has been systematacially studied. SA (10 mg/L) could be totally removed with 1.5 kGy irradiation. Quenching experiments demonstrated that •OH and e_aq^- were the predominant for SA degradation. SA degradation was reduced with initial concentration increasing, and the removal was faster with pH increasing in the range of 3.1-10.8. The coexisting matters affected SA degradation through changing reactive species, and the introduction of SO₄^2- and Cl^- enhanced SA degradation, while CO₃^2- had a negative impact on SA degradation, and the degradation was insignificantly affected when adding humic acid. Gamma irradiation could remain effective in real water matrixes. In conjunction with LC-MS analysis and DFT calculation, possible degradation pathways for SA were proposed. Gamma irradiation could reduce the toxicity of SA, while several byproducts with more toxic were also formed. Furthermore, gamma/priodate (PI) process was promising to enhance SA degradation and mineralization. k value increased by 1.85 times, and mineralization rate increased from 19.51% to 79.19% when adding PI. This study suggested that ionizing radiation was efficient to eliminate SA in wastewater.