Synergistic activation of peroxymonosulfate by highly dispersed iron-based sulfur–nitrogen co-doped porous carbon for bisphenol a removal: mechanistic insights and selective oxidation

Abstract

Efficient and pervasive solutions are urgently needed to mitigate pollution from emerging contaminants in aquatic environments. Activation of peroxymonosulfate (PMS) is commonly employed to remove refractory organic pollutants from water. Herein, we synthesized sulfur–nitrogen co-doped porous carbon materials loaded with highly dispersed iron species (FeSNC) using template-assisted and ligand site construction methods. The uniform doping of N, S, and Fe in the carbon substrate, along with their synergistic effects, significantly enhanced catalytic activity by creating a high degree of defects in the catalyst (I_D/I_G = 1.47). This enhancement facilitated efficient removal of BPA, achieving an apparent rate constant of up to 2.83 min⁻¹, which was 30 times higher than that of SNC and 6 times higher than that of FeNC. The FeSNC/PMS system demonstrated robust catalytic stability across the pH 3–9 range, and showed minimal sensitivity to environmental factors like the aqueous matrix, with low iron ion dissolution (<0.01 mg L⁻¹) and certain reusability. Mechanistic investigations employing quenching experiments, EPR tests, probe experiments, and electrochemical tests elucidated that the system catalyzed the degradation of BPA via two non-radical pathways: high-valent iron oxidation and singlet oxygen pathways. Additionally, the system further exhibits selective degradation of electron-rich organics (e.g., 4-chlorophenol, sulfamethoxazole, ofloxacin, etc.).