Fig. 6: Evaluation of As^III oxidation performance and mechanism in different water matrices using Fe-N-C-based catalytic systems.

a Variation in As^V concentration during the oxidation of As^III in a deionized water matrix using PMS/Fe-N-C and PDS/Fe-N-C (the complete data in Supplementary Table 2). b Schematic diagram illustrating the energy barrier for the one-electron oxidation of As^III to As^IV and the direct oxygen atom transfer process. c Time-dependent IR spectra collected on a bare diamond ATR crystal in As^III buffer solution, showing PMS diffusion without reaction. d The time-dependent IR spectra of As^III oxidation by Fe-N-C/PMS, simultaneously capturing the diffusion and reaction of PMS. The right panel presents a magnified infrared region highlighting the Fe^IV = O band. e Variation of As^V concentration (solid line) and chemical oxygen demand (COD) (dashed line) during the removal of As^III in a real lake water matrix (the complete data in Supplementary Table 3). The error bars in Fig. 6a and e are based on data from at least three parallel experiments. Experimental conditions for As^III removal in panels (a) and (e): [As^III] = 20 μM; [PMS] or [PDS] = 50 μM; [Fe-N-C] = 50 mg·L⁻¹. Source data for Fig. 6a, c-e are provided as a Source Data file.