Efficient removal of norfloxacin in water by sulfidated nanoscale zerovalent iron loaded nitrogen-doped biochar: Dual realization of efficient enrichment and reduction

In this study, a nitrogen-doped biochar loaded with sulfidated nanoscale zero- valent iron (S-nZVI@NBC) was synthesized using reed as the precursor to efficiently remove norfloxacin (NOR) from water. S-nZVI@NBC could completely remove NOR within 180 min at a removal rate of 0.026 min−1, exceeding the performance of materials without sulfur or nitrogen species. Density functional theory calculation showed that S-nZVI@NBC had strong NOR adsorption performance (−2.075 eV) and better electron transfer capacity (0.449 e). The nitrogen and sulfur species in S-nZVI@NBC promote the degradation of NOR by H* (dominant, 97.4 %) and direct electron transfer (DET) (synergistic, 2.6 %) pathways. In addition, XPS analysis further showed that sulfur species promoted iron cycling with the assistance of nitrogen species in the reaction, making S-nZVI@NBC had better removal performance to pollutants and practical application potential. The removal efficiency of NOR could still be maintained at about 60 % after 6 cycles, which might benefit from the dual protection of nitrogen-doped carbon network and sulfur shell. Piperazine ring cleavage and defluorination were the main ways of the NOR degradation by S-nZVI@NBC, thus reducing the biotoxicity of NOR. This study clarified the reaction mechanism of S-nZVI and nitrogen species to promote the degradation of pollutants by heterogeneous materials, thereby providing a theoretical foundation for the synthesis and application of the integrated adsorption/degradation materials.