Nitrogen Vacancy-Modulated Peroxymonosulfate Nonradical Activation for Organic Contaminant Removal via High-Valent Cobalt-Oxo Species

Abstract

Rapid generation of high-valent cobalt-oxo species (Co(IV)═O) for the removal of organic contaminants has been challenging because of the low conversion efficiency of Co(III)/Co(II) and the high activation energy barrier of the Co(II)-oxidant complex. Herein, we introduced nitrogen (N) vacancies into graphite carbon nitride imbedded with cobalt carbonate (CCH/CN-V_<i>n</i>) in a peroxymonosulfate (PMS)/visible light system to break the limitations of a conventional two-electron transfer path. These N vacancies enhanced the electron distribution of the Co 3d orbital and lowered the energy barrier to cleave the O-O bond of PMS in the Co(II)-PMS complex, achieving the modulation of major active species from ¹O₂ to Co(IV)═O. The developed synergistic system that exhibited adsorption and oxidation showed remarkable selectivity and contaminant removal performance in inorganic (Cl^-, NO₃^-, HCO₃^-, and HPO₄^-) organic (HA) and even practical aqueous matrices (tap water and secondary effluent). This study provides a novel mechanistic perspective to modulate the nonradical path for refractory contaminant treatment via defect engineering.