Abstract
In situ chemical oxidation (ISCO) is commonly used for the remediation of contaminated sites, and molecular oxygen (O(2)) 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 O(2) activation due to their prominent catalytic performance, wide availability, and environmental compatibility. This review provides a timely overview on O(2) 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 O(2) activation are systematically summarized, including the electron transfer pathways, reactive oxygen species formation, and the transformation of the materials during O(2) activation, highlighting the effects of the coordination state of Fe atoms on the capability of the materials to activate O(2). In addition, the key factors influencing the O(2) activation process are analyzed, particularly the effects of organic ligands. This review deepens our understanding of the mechanisms of O(2) activation by Fe-based materials and provides further insights into the application of this process for in situ remediation of organic-contaminated sites.