A Review of the Mechanisms of Single-Atom-Based Advanced Oxidation Processes for the Degradation of Persistent Organic Pollutants in Water Environments

Single-atom catalysts (SACs) have emerged as highly efficient and cost-effective catalysts, becoming pivotal materials in catalytic processes. The functional structure of SACs is the metal active center of the support structure, and the catalytic mechanism of SACs formed by each metal is different. This review begins by categorizing SACs based on various synthesis strategies and provides a comparative analysis of their structural and functional differences. Subsequently, the catalytic mechanisms of SACs in the Fenton system, persulfate system, and photocatalytic system were further discussed and reviewed. The excellent removal efficiency of persistent organic pollutants depends on the type and concentration of reactive oxygen species, including sulfate radical, hydroxyl radical, superoxide anion, and singlet oxygen. The advantages of different supported SACs in advanced oxidation processes (AOPs) are also summarized, including carbon materials, metals, and metal oxides. Finally, it addresses the opportunities and challenges faced by SACs in AOP applications and outlines potential directions for future research and development.