(513dm) Switching H2O2 Activation Pathway upon K+ Intercalation into Feocl Toward Oxidative Coupling of Organic Contaminant

Traditional advanced oxidation processes (AOPs), such as Fenton oxidaiton, rely on the generated strong oxidizing radical species to degrade organic pollutants. However, the drawbacks of using AOPs include low radical yield, toxic by-product generation and the wasteful transformation of potential organic resources into greenhouse emissions. The development of non-radical oixdative degradation processes provides a possibility to solve these problems. Some enzymes, such as Horseradish Peroxidase (HRP) and Laccase, were considered for this purpose. They can react with oxidants to generate surface active species rather than radical species, leading to the oxidative polymerization of the organic pollutants, and then the formed insoluble polymers can be removed through physical separation. In this report, we used an oxidative intercalation method to tunably introduce potassium cations (K⁺) into the van der Waals interlayer of a catalytically active iron oxychloride (FeOCl) host. The prepared K-intercalated FeOCl (K-FeOCl) achieves the enzyme-like pollutant oxidation using H₂O₂ as oxidant, which shows high H₂O₂ utilization efficiency and excellent reactivity for many pollutants including phenols, anilines and pharmaceuticals. The intermediate products were investigated by LC-MS/MS during guaiacol (2-MeOP) oxidation, confirming the oxidative polymerization pathway. Based on this pathway, a novel “polymerization-filtration” process was designed for the removal of 2-MeOP. TOC was completely removed within 4 hrs under our K-FeOCl system, which is even fasrer than HRP system. Further, mechanistic evidence suggests that the intercalation of K⁺ changed the electronic structure of Fe-active sites on FeOCl, which promotes the formation of surface ferryl-oxo active species that is very similar to the active structure of enzyme. The good pollutant removal capability and stability of the K-FeOCl system exhibited its great potential as alternative of fragile enzymes for municipal and industrial wastewater treatment. And the intercalation-induced change of reaction behavior deepened our understanding on the reactivity of Fe sites in heterogeneous catalysis.