Nitrogen-boron co-doped carbon directs nonradical activation pathway of persulfate: ¹O₂-dominated efficient...

The textile industry generates substantial volumes of recalcitrant azo dye wastewater, demanding advanced oxidation strategies beyond conventional methods. This study addresses the inefficiency of existing degradation techniques by developing defect-enriched nitrogen/boron co-doped carbon (N,B-C) via a facile one-step pyrolysis approach. The synthesized material redirects persulfate activation toward a highly efficient nonradical pathway, overcoming limitations of symmetric peroxydisulfate (PDS) activation inherent in conventional nonmetallic catalysts. Comprehensive characterization revealed that N,B-C possesses a three-dimensional porous architecture (pore size: 9.07-48.77 nm) providing abundant active sites, while boron doping induces significant structural defects (ID/IG = 1.47) and creates synergistic B-N dipolar configurations. These features collectively enhance degradation efficiency and lower the O-O bond cleavage energy barrier. Degradation experiments demonstrated exceptional performance: the N,B-C/PS system achieved 97.49 % removal of Reactive Red 2 (RR2) within 30 min, with a pseudo-first-order kinetic constant (k = 0.234 min^-1) surpassing N/S- and N/P-co-doped materials by two orders of magnitude (0.0012-0.0016 min^-1). Quenching tests and electron paramagnetic resonance (EPR) analysis conclusively identified singlet oxygen (¹O₂) as the dominant reactive species (>80 % contribution), with minimal involvement of radical pathways (SO₄·^-/·OH). The system maintained robust efficiency across a broad pH range (3-9) and in complex real water matrices (tap water/lake water, >78.9 % removal). Furthermore, the catalyst retained 71.39 % activity after four cycles. This work provides a sustainable, metal-free strategy for designing carbon catalysts that directionally regulate PS activation toward nonradical pathways, offering significant potential for practical textile wastewater remediation.