Elucidating the multi-channel activation mechanism of an N/S-doped biochar/peracetic acid system for sulfonamide antibiotic degradation

N/NS co-doping boosts PAA activation, removing 97.5% sulfonamides in 30 min. • EPR and electrochemistry verify dual-channel degradation dominated by 1 O 2 . • DFT confirms 1 O 2 -induced N-S scission and ring opening mitigate toxicity. • DOM-antibiotic complexation negligibly impacts degradation efficiency. Element-doped biochar has emerged as an effective catalyst for activating peracetic acid (PAA) toward antibiotic degradation. However, the electron transfer processes occurring at the biochar interface remain insufficiently understood. In this study, N-doped biochar (NBC) and N/S co-doped biochar (NSBC) are employed to efficiently degrade sulfonamide antibiotics through PAA activation. Active sites, including pyridinic N, thiophene S, and graphitic defects, synergistically promote PAA activation, preferentially generating singlet oxygen ( 1 O 2 ) accompanied by •OH and O 2 •− . Radical and non-radical pathways operate simultaneously, resulting in an average removal efficiency of 97.45% for the target sulfonamides within 30 min. Quenching experiments, electron paramagnetic resonance, and electrochemical analyses collectively confirm the dual-pathway activation mechanism. Liquid chromatography-mass spectrometry combined with density functional theory calculations reveals that the main transformation pathways involve S N bond cleavage, aromatic ring opening, and hydroxylation reactions. Toxicity prediction and plant growth assays further demonstrate a significant reduction in the overall toxicity of the degradation intermediates. In addition, dissolved organic matter released during the biochar reaction process forms complexes with sulfonamide antibiotics, although these interactions are insufficient to substantially affect antibiotic degradation efficiency. Overall, this study not only elucidates the multi-channel activation mechanism of the NBC/NSBC-PAA system but also provides experimental support for the practical application of biochar-based catalytic systems in water purification. Download: Download high-res image (110KB) Download: Download full-size image