Catalytic activation of peroxydisulfate by alfalfa-derived nitrogen self-doped porous carbon supported CuFeO2 for nimesulide degradation: Performance, mechanism and DFT calculation

[Display omitted] •CuFeO2/NPC composites were prepared at no nitrogen sources and reductant.•CuFeO2/NPC can effectively activate PDS to degrade nimesulide.•The OH, SO4- and 1O2 were the main reactive species for nimesulide degradation.•Mechanism of PDS activated by CuFeO2/NPC was clarified in detail.•Degradation pathway was proposed combined with HPLC/MS spectra and DFT calculation. The nitrogen self-doped porous carbons (NPCs) were prepared using alfalfa as raw material by pyrolysis method without additional nitrogen sources at various pyrolysis temperatures. The NPC supported CuFeO2 (CuFeO2/NPC) composites with large BET surface area (113.18 - 517.56 m2 g−1) were successfully prepared by hydrothermal method without reductant. The NPC prepared at 600 °C (NPC-600) supported CuFeO2 (CuFeO2/NPC-600) possessed the highest catalytic performance for activating peroxydisulfate (PDS) to degrade nimesulide compared to other CuFeO2/NPC composites. The OH, SO4- and 1O2 were the main reactive species for nimesulide degradation. The oxygen-containing functional groups, pyridinic N, graphitic N, and Fe3+/Fe2+ and Cu2+/Cu+ redox cycles were demonstrated to be extremely important in activating PDS to produce reactive species. The degradation pathway of nimesulide was proposed combined with the HPLC/MS spectra and DFT calculation, and the overall toxicity of nimesulide were effectively alleviated in CuFeO2/NPC-600+PDS system according to toxicity prediction.