Enhanced sulfamethoxazole degradation by peroxymonosulfate activation with sulfide-modified microscale zero-valent iron (S-mFe0): Performance, mechanisms, and the role of sulfur species

Abstract Sulfide-modified microscale zero-valent iron (S-mFe 0 ) was applied to activate peroxymonosulfate (PMS) to degrade sulfamethoxazole (SMX), a typical sulfonamide bacteriostatic antibiotic. In this work, the effects of S/Fe molar ratio, S-mFe 0 dosage, PMS dosage, different initial pH value, dissolved oxygen, SMX concentration and inorganic ions on SMX removal by S-mFe 0 /PMS system were investigated, respectively. Besides, the role of sulfur species (including the FeS, SO 3 2− , S 2− ) was studied. In contrast to mFe 0 /PMS system, the removal efficiency of SMX obtained by S-mFe 0 /PMS system was increased by 29.4%. Radical quenching and Electron Paramagnetic Resonance spectroscope (EPR) tests identified that both OH and SO 4 − were committed to degrading SMX, and SO 4 − was proven to be the dominant one. The electrochemical analysis of S-mFe 0 and bare mFe 0 , implying a better electron transfer ability of S-mFe 0 due to the formation of FeS. Furthermore, the activation of S 2− for PMS could be ruled out by EPR tests results. Conversely, SO 3 2− could effectively activate PMS to generate reactive oxygen species (ROS). The catalytic mechanisms of S-mFe 0 /PMS system were clarified by SEM-EDS, XRD, XPS, radical quenching and EPR tests. Based on the detected intermediates via LC-TOF-MS/MS, the degradation pathways of SMX by S-mFe 0 /PMS system were proposed. Overall, the work suggests that S-mFe 0 /PMS system has a good potential for the elimination of micropollutants in the aquatic environment.