Recent Progress in Molecular Oxygen Activation by Iron-Based Materials: Prospects for Nano-Enabled In Situ Remediation of Organic-Contaminated Sites.

In situ chemical oxidation (ISCO) is commonly used for the remediation of contaminated sites, and molecular oxygen (O₂) after activation by aquifer constituents and artificial remediation agents has displayed potential for efficient and selective removal of soil and groundwater contaminants via ISCO. In particular, Fe-based materials are actively investigated for O₂ activation due to their prominent catalytic performance, wide availability, and environmental compatibility. This review provides a timely overview on O₂ activation by Fe-based materials (including zero-valent iron-based materials, iron sulfides, iron (oxyhydr)oxides, and Fe-containing clay minerals) for degradation of organic pollutants. The mechanisms of O₂ activation are systematically summarized, including the electron transfer pathways, reactive oxygen species formation, and the transformation of the materials during O₂ activation, highlighting the effects of the coordination state of Fe atoms on the capability of the materials to activate O₂. In addition, the key factors influencing the O₂ activation process are analyzed, particularly the effects of organic ligands. This review deepens our understanding of the mechanisms of O₂ activation by Fe-based materials and provides further insights into the application of this process for in situ remediation of organic-contaminated sites.