Coupling-promoted oxidative degradation of organic micropollutants by iron oxychloride (FeOCl) with dual active sites
Jinling Wang, Shifa Zhong, Yuzhen Wen, Jianan Li, Hualin Wang, Honglai Liu, Changzheng Cui, Ming Gong, Huichun Zhang, Xuejing Yang
Abstract
Heterogeneous Fenton has emerged as a profitable solution for contaminant removal via advanced oxidation processes (AOPs). Besides the dominant hydroxyl radicals (HO•), some weaker oxidants, such as ferryl-oxo species (Fe(IV)=O) species, can also be produced during the surface H2O2 activation, but its function is not well understood. In this study, we developed a vanadium-etched iron oxychloride (V-FeOCl) catalyst that simultaneously incorporates Fenton-like sites and peroxidase-like (Fe(IV)=O) sites. The derived V-FeOCl material showed 2.8–5.4 times enhancement of the pseudo-first-order rate constant for various recalcitrant organic micropollutants. Most importantly, the activity demonstrated an intriguing induction period for the TOC removal as well as a rocketed kinetics after the induction. This induction period was further attributed to the oxidative coupling of the organic monomers, as revealed by the identification of dimers using UPLC-MS. The coupling intermediates were demonstrated to be more susceptible to HO• radical attack via the high-throughput prediction of the HO• radical rate constants of 94 possible coupling intermediates using machine learning. These findings clarified the key role of Fe(IV)=O in the HO•-based oxidation process and points to a novel coupling-enhanced degradation pathway, which could potentially pave a new avenue of oxidative transformations for catalytic and environmental applications.