Active Hydrogen-Mediated Radical/Nonradical Reactions in Confined Nano Zero-Valent Iron for Ultrafast Micropollutant Decontamination

The development of efficient catalysts for peroxymonosulfate (PMS) activation, particularly at ultralow oxidant concentrations, remains a critical challenge for sustainable water treatment. Here, we report a novel composite catalyst (C-nZVI/Sep) designed for the efficient activation of PMS at ultralow concentrations. The catalyst was synthesized via a facile impregnation-calcination method, enabling the ordered loading of carbon-encapsulated nano zerovalent iron (nZVI) onto a sepiolite (Sep) support. Remarkably, with only 0.05 mM PMS, the C-nZVI/Sep/PMS system achieved near-complete removal (99.3%) of acetaminophen within 4 min. The observed degradation rate constant (K-value) of 1024.68 min–1 M–1 significantly outperforms previously reported catalysts. Comprehensive mechanistic studies revealed that the carbon-coated nZVI structure facilitates a continuous electron supply, facilitating proton (H+) conversion to active hydrogen (•H). This, in turn, drives the partial transformation of superoxide radicals (•O2–) into singlet oxygen (1O2), creating a synergistic pathway for rapid ACE degradation. Long-term flow-through column tests demonstrated exceptional stability with zero iron leaching (below the detection limit) over 25 days, underscoring the system’s environmental compatibility and practical potential. This study presents a low-cost, scalable strategy to advance PMS-based advanced oxidation processes for efficient and sustainable wastewater treatment.