Highly Efficient Degradation of Bisphenol A by Peroxymonosulfate Activation Using Bamboo Kraft Lignin Single-Atom Catalyst

A nitrogen-coordinated Fe single-atom catalyst (SA Fe-N/C) is synthesized using a homogeneous ethanol-based dissolution system with bamboo kraft lignin serving as the carbon source. Uniformly dispersed Fe atoms with an interatomic distance of less than 2 Å throughout the SA Fe-N/C structure are revealed through X-ray absorption spectral analysis and HAADF-STEM images, which possessed a high Fe loading of 2.69%. The degradation rate of bisphenol A (BPA) approached 99% within 5 min, with the observed rate constant (k_obs) of the catalysts markedly increasing from 0.070 to 0.615 min⁻¹. The catalyst-mediated electron transfer pathway is identified as the predominant mechanism for BPA degradation. Both experimental data and DFT analysis of the nitrogen ligands demonstrated that pyridinic N-coordinated Fe single atoms are the principal active sites, attributed to the enhanced electron density and delocalization concentrated around the Fe sites. These findings significantly elucidate the role of nitrogen ligands in designing efficient lignin-derived carbon single-atom catalysts for environmental applications.