Synthesis of N-doped porous carbon derived from biomass waste for activating peroxymonosulfate in water decontamination: mechanism insight and biotoxicity assessment

Abstract

N-doping is a widely used strategy for the synthesis of highly efficient carbon nanocatalysts; however, an in-depth understanding of the effect of nitrogen source on the intrinsic structure and catalytic performance is highly desired. Therefore, to kill two birds with one stone, a series of N-doped carbon nanomaterials were synthesized by the pyrolysis of biomass waste (dealkaline lignin) and various nitrogen sources (including melamine, dicyandiamide, and urea). Even though N-doped nanocatalysts showed better catalytic activity than HCNs (pyrolysis of only dealkaline lignin) for sulfamethoxazole (SMX) degradation via peroxymonosulfate (PMS) activation, NCN-1 and NCN-2 presented contractive and small spherical structures when melamine and dicyandiamide with high nitrogen content were added, showing relatively low catalytic efficiency. NPCN derived from dealkaline lignin and urea led to the formation of a porous cluster structure with abundant active species of graphitic C/N and C–OH, which showed the best catalytic performance for SMX degradation. Significantly, NPCN exhibited excellent universality, adaptability, and reusability. Moreover, the possible mechanism was proposed based on quenching study, electron paramagnetic resonance (EPR) analysis, electronic quenching experiment, density functional theory (DFT) calculation, and high-resolution mass spectrometry (HR-MS), confirming that e, ¹O₂, ·OH, SO₄˙⁻, and O₂˙⁻ were the active species, of which ¹O₂ was the dominant one in the NPCN/PMS system. In addition, the biotoxicity of SMX was evaluated by ecological structure–activity-relationship model (ECOSAR) analysis and germination tests of wheat seeds. This work provides how the nitrogen source would affect the microstructure-dependent catalytic activity of metal-free carbon nanocatalysts for water decontamination.