Metal-based Catalysts for Non-radical Advanced Oxidation Processes

<jats:p>In recent years, considerable attention in environmental remediation has been directed toward advanced oxidation processes (AOPs) for their adaptability and efficiency in degrading recalcitrant and emerging organic compounds, such as pharmaceuticals and pesticides. Among the various materials investigated, metal-based catalysts have drawn significant interest due to their chemical stability, catalytic efficiency, and cost-effectiveness. Non-radical mediated AOPs are viewed as a promising approach for wastewater treatment due to their strong resistance to water matrix interference in real-world applications. Radical oxidation, driven by hydroxyl (HO˙) and sulfate (SO4˙−) radicals, offers high redox potential and effective mineralization. However, in wastewater with high halide concentrations, it may lead to toxic halogenated by-products. Non-radical pathways in AOPs, involving singlet oxygen, surface-activated complexes, high-valent metal species, and direct electron transfer, provide an alternative with lower by-product formation. Although they have lower redox potentials, non-radical species offer selective pollutant degradation, reduced matrix interference, and broad pH stability, making them more suitable for practical wastewater treatment. This chapter explores recent advances in metal-based catalysts for non-radical AOPs in removing emerging organic pollutants. It examines non-radical species generation mechanisms, key challenges, and research gaps. Methods for identifying non-radical pathways, including quenching test, EPR spectroscopy, D2O substitution, and electrochemical methods, are discussed. Future research directions and the potential for large-scale wastewater treatment applications are also highlighted.</jats:p>