Asymmetric Fe–V Diatomic Pair Interplays Steering Mineralization/Polymerization Pathways via High-Valent Metal-Oxo Intermediates for Water Purification

Abstract

Mineralization and polymerization represent two pollutant transformation pathways with unique advantages in advanced oxidation processes. However, the in-depth understanding of the control strategies and underlying mechanisms controlling mineralization and polymerization remains limited. Herein, the catalyst with an asymmetric Fe–V diatomic pair (FeV-NC) was developed to activate peroxymonosulfate (PMS), which displayed excellent performance in phenol removal (100% within 10 min). Characterizations and theoretical calculations revealed that the Fe–V distance (∼2.955 Å) is well matched with the O1–O3 distance in PMS (∼2.948 Å), enabling a bridged bidentate adsorption configuration that forms a dual-oxygen adsorption site. This configuration accelerates electron transfer from the catalyst to PMS and lowers the energy barrier for PMS decomposition. 18O isotope labeling and in situ Raman spectroscopy confirmed that high-valent metal-oxo species (FeIV–O–VV in FeV-NC/PMS system and FeV=O in Fe-NC/PMS system) were the main reactive oxygen species. Especially, the inferior oxidizing capacity of FeIV–O–VV (−0.04 e–) relative to that of FeV=O (−0.86 e–) led to an enhanced phenol polymerization ratio (∼90%) in the FeV-NC/PMS system. Furthermore, scaled-up continuous-flow experiments confirmed the robust operational stability of the FeV-NC/PMS system and the low toxicity of the treated effluent. This study provides novel insights into the regulatory mechanism of pollutant conversion pathways in Fenton-like reactions.