In-situ nitrogen-doped phenolic resin-based carbon nanospheres as efficient peroxymonosulfate activators for BPA degradation

The persistent threat of emerging contaminants (ECs) in aquatic ecosystems necessitates advanced water purification strategies. Peroxymonosulfate (PMS)-activated advanced oxidation processes (AOPs) have emerged as promising solutions, where non-metallic heteroatom-doped carbon catalysts demonstrate enhanced PMS activation capabilities. However, reconciling high catalytic efficiency with long-term stability in metal-free systems remains challenging. Herein, we develop monodisperse nitrogen-doped carbon nanospheres (NCS) through a facile in situ doping strategy. This approach involves the synthesis of spherical resorcinol-formaldehyde resin via the Stöber method using resorcinol as the carbon source and melamine as the nitrogen source, followed by controlled carbonization. By systematically adjusting the resorcinol/melamine ratio, we achieved precise regulation of nitrogen configurations, obtaining NCS-3 with optimal N content (5.3 at %). Remarkably, the NCS-3/PMS system exhibited ultrafast bisphenol A (BPA) degradation (100 % removal within 15 min, rate constant = 0.346 min −1 ) across a broad pH range (3.0–11.0), while maintaining exceptional tolerance to coexisting anions. Through multi-spectroscopic investigations and mechanistic analyses, we elucidated a dual-pathway activation mechanism: Dominant nonradical process mediated by singlet oxygen ( 1 O₂) synergized with auxiliary radical pathway (O 2 ·- ). Experimental and theoretical evidence confirmed that pyridinic N serves as the primary catalytic center, promoting PMS adsorption/activation through enhanced charge redistribution. This work provides critical insights for designing high-performance metal-free catalysts and advances the mechanistic understanding of active site engineering in carbon-based PMS activation systems.