<i>κ</i>-carrageenan-derived N-, S-codoped porous carbon promotes peroxymonosulfate activation for norfloxacin degradation

Abstract

Developing high-performance, sustainable carbon-based catalysts for degrading refractory organic pollutants is of critical significance in environmental remediation. Presented herein is a new metal-free N- and S-codoped porous carbon (NSPC) by utilizing κ-carrageenan (a natural marine biomass with intrinsic sulfate groups) as a dual source of sulfur and carbon, alongside melamine (the N source) and K₂CO₃ (the activator). This approach avoided the reliance on toxic exogenous sulfur reagents, simplifying the synthesis process while enhancing sustainability. The synthesized NSPC-700 exhibited a high specific surface area of 1,219.31 m² g^–1 and abundant active sites (graphitic N and thiophenic S), achieving an exceptional norfloxacin (NOR) removal efficiency of 97.16% and a mineralization efficiency of 49.30% within 90 min. Mechanistic studies identified graphitic N and thiophenic S as key active sites, and revealed that the degradation was dominated by non-radical pathways, specifically singlet oxygen (¹O₂) and electron transfer (total contribution > 84%). Furthermore, NSPC-700 demonstrated excellent practical potential: it maintained an 89.00% NOR removal efficiency in a continuous-flow system over 5 h and retained a 90.36% removal efficiency after five consecutive cycles. This work highlights the innovative use of intrinsic sulfur-source biomass to transform into a value-added carbon catalyst, offering a green, sustainable strategy for antibiotic wastewater remediation.