High-valent iron-oxo species mediated cyclic oxidation through single-atom Fe-N6 sites with high peroxymonosulfate utilization rate

Fe singly anchored onto graphite carbon nitride (Fe-SA/PHCNS) as Fe-N6 was synthesized to realize efficient peroxymonosulfate (PMS) activation and superior organic pollutant oxidation. The Fe-N6 was the core catalytic site of activation via forming high-valent iron–oxo species (FeN6 =O) as the transient reactive intermediate as evidenced by X-ray adsorption fine spectroscopy (XAFS), in-situ Raman spectrum and theoretical calculation. The cycle of Fe-N6 and FeN6 =O interconversion was sustainably observed with organic pollutant as the electron-donor and PMS as the electron-acceptor. As results, the equivalent steady state concentration of FeN6 =O was as high as 2.39 × 10−8 M and this system exhibited 97.2% average PMS utilization rate. Fe-SA/PHCNS can be immobilized onto carbon felt for the simultaneous filtration and oxidation with stable and efficient performance. This study elucidated the mechanism and superiority of FeN6 =O mediated oxidation pathway and can advance the research and application of this new approach in advanced oxidation processes.