Simultaneous elimination of sulfonamides and antibiotic resistance genes via peroxymonosulfate activation by ligand-modulated iron sites on biochar: The critical role of interfacial EDTA complexation

Heterogeneous iron-based catalytic systems for peroxymonosulfate (PMS) activation typically suffer from iron active site passivation and severe metal leaching. In this study, a novel self-assembled tobacco straw biochar featuring interfacial EDTA-chelated iron centers (EDTA@FTBC) was synthesized with highly stable ligand-modulated active sites. The multi-dentate coordination structure stabilized the iron active sites, effectively reducing metal leaching and ensuring excellent reusability. The PMS/EDTA@FTBC system achieved 94.5% sulfamethoxazole degradation, exhibiting broad-spectrum efficiency and robust anti-interference capability in complex aqueous environments. Characterization and DFT calculations revealed that interfacial chelation optimized surface oxygen functional groups and iron center electron density, lowering the electron transfer energy barrier to sustain a continuous Fe(II)/Fe(III) cycle. Strong non-covalent interactions promoted the oriented adsorption of PMS onto the EDTA@FTBC surface, elongating the peroxide O O bond from 1.33 Å to 1.45 Å for highly efficient activation. Surface-bound non-radical pathways dominated, driven by 1 O 2 and direct electron transfer via a metastable surface complex. Beyond efficient elimination of sulfonamides, the system achieved 77.1% mortality of antibiotic-resistant bacteria within 120 min and effectively reduced the relative abundances of resistance genes. This study provided a novel ligand-modulated biochar technology for PMS activation, offering an efficient approach for the concurrent elimination of sulfonamides and resistance genes.