Synergistic Activation of Peroxymonosulfate over Dual-Etched Hierarchical Biochar by Mesopore-Dominated Non-Radical Pathways for Efficient Nimesulide Removal

Abstract

Rational design of hierarchical pore architectures in biomass-derived carbon remains a critical scientific challenge for enhancing catalytic performance. This study pioneers a novel dual-etching strategy combining H3PO4 chemical pre-etching with plasma physical re-etching to construct a wheat straw charcoal catalyst (E-EWC) for optimizing peroxymonosulfate (PMS) activation efficiency to degrade organic pollutants. Morphological and pore structure analysis revealed the synergistic effect of this dual-etching process on constructing a continuous hierarchical channel structure interconnecting micro- and mesopores of E-EWC, which facilitates PMS activation and accelerates electron transfer. Meanwhile, quantitative structure–activity correlation analysis indicated that mesopore volume more favorably promotes nimesulide (NIM) degradation (R2 = 0.8511). Consequently, E-EWC achieved a satisfactory 97% removal rate of NIM within 60 min primarily by non-free-radical pathways and electron transfer, whose degradation kinetic constant was approximately 3- and 4-fold higher than those of single-etched EWC and E-WC catalysts, respectively. Furthermore, E-EWC’s superior chemical stability, strong anti-interference ability, and low toxicity of NIM degradation intermediates collectively demonstrate it as an effective PMS activator for water treatment applications. This work not only elucidates the critical role of hierarchical porosity in non-radical PMS activation but also provides an efficient strategy for designing advanced carbon catalysts for water remediation.