Activation of Molecular Oxygen by Electron-Rich Materials for Sustainable Soil Remediation

Traditional advanced oxidation processes (AOPs) in soil remediation rely on external chemical oxidants, which have evident drawbacks of high cost, soil structure disruption, and high carbon footprint. Compared to traditional AOPs, molecular oxygen (O₂) activation requires no external reagents, and can realize environment-friendly oxidation with inexhaustible O₂ resources. Electron-rich materials can activate O₂ to generate reactive oxygen species (ROS) to achieve in situ remediation of soil pollution. However, there is lack of knowledge about O₂-mediated oxygenation reactions for pollutant removal in soil. Therefore, this review systematically investigated the common electron-rich materials that can be used for O₂ activation in soil, including iron-based materials, bismuth-based materials, copper-based materials, and porous carbon. The mechanisms of O₂ activation by these materials are summarized. Multiple methods, including vacancy defect, heteroatom doping, and edge defect can be applied to modify these materials for improving their electron transfer capacities toward O₂ activation. The applications of electron-rich materials-driven O₂ activation in soil remediation are discussed, and pH, oxygen content, organic matter, and sunlight intensity are identified as main influencing factors on ROS generation for pollutant removal. The outcomes will provide important implications for the development of O₂-mediated oxygenation technology to achieve sustainable and efficient soil remediation.