A Mechanistic Understanding of Hydrogen Peroxide Decomposition by Vanadium Minerals for Diethyl Phthalate Degradation

The interaction of naturally occurring minerals with H₂O₂ affects the remediation efficiency of polluted sites in in situ chemical oxidation (ISCO) treatments. However, interactions between vanadium(V) minerals and H₂O₂ have rarely been explored. In this study, H₂O₂ decomposition by various vanadium-containing minerals including V(III), V(IV), and V(V) oxides was examined, and the mechanism of hydroxyl radical (^•OH) generation for contaminant degradation was studied. Vanadium minerals were found to catalyze H₂O₂ decomposition efficiently to produce ^•OH for diethyl phthalate (DEP) degradation in both aqueous solutions with a wide pH range and in soil slurry. Electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) analyses, and free radical quenching studies suggested that ^•OH was produced via single electron transfer from V(III)/V(IV) to H₂O₂ followed a Fenton-like pathway on the surface of V₂O₃ and VO₂ particles, whereas the oxygen vacancy (OV) was mainly responsible for ^•OH formation on the surface of V₂O₅ particles. This study provides new insight into the mechanism of interactions between vanadium minerals and H₂O₂ during H₂O₂-based ISCO.