High-valent metal species (iron, manganese, cobalt, copper, and ruthenium) based advanced oxidation processes (AOPs) have emerged as sustainable technologies for water remediation. These processes offer high selectivity, electron transfer efficiency, and compatibility with circular chemistry principles compared to conventional systems. This comprehensive review discusses recent advances in the synthesis, stabilization, and catalytic applications of high-valent metals in aqueous environments. This study highlights their dual functionality, not only as conventional oxidants but also as mechanistic mediators within redox cycles that underpin next-generation AOPs. In this review, the formation mechanisms of these species in various oxidant systems are critically evaluated, highlighting the significance of ligand design, supramolecular confinement, and single-atom engineering in enhancing their stability. The integration of high-valent metal-based AOPs into photocatalysis, sonocatalysis, and electrochemical regeneration is explored through a newly proposed classification framework, highlighting their potential in the development of energy efficient hybrid systems. In addition, this work addresses the critical yet underexplored area of environmental fate, elucidating the post-oxidation transformation pathways of high-valent species, with particular attention to their implications for metal recovery and nutrient valorization. This review highlights the potential of high-valent metal-based AOPs as a promising approach for zero wastewater treatment within circular economies. Future frontiers, including bioinspired catalyst design, machine learning-guided optimization, and closed loop reactor engineering, will bridge the gap between laboratory research and real-world applications.

High-valent metal species such as Fe(IV), Mn(V), Co(IV), and Cu(III) based advanced oxidation processes (AOPs) have emerged as sustainable technologies for water remediation. These processes offer high selectivity, electron transfer efficiency, and compatibility with circular chemistry principles compared to conventional radical-driven systems. This comprehensive review discusses recent advances in the synthesis, stabilization, and catalytic applications of high-valent metals in aqueous environments. Here the focus is on their role not only as conventional oxidants, but also as mechanistic mediators of redox cycles in next-generation AOPs. In this review, the formation mechanisms of these species in various oxidant systems (peroxymonosulfate, peracetic acid, periodate) are critically evaluated, highlighting the significance of ligand design, supramolecular confinement, and single-atom engineering in enhancing their stability. The integration of high-valent metal AOPs into photocatalysis, sono-catalysis, and electrochemical regeneration is examined through a newly proposed classification framework, emphasizing their potential for energy-efficient hybrid systems. Furthermore, we address the critical yet underexplored domain of environmental fate, detailing the post-oxidation transformation pathways of high-valent species and their potential for metal recovery and nutrient valorization. By bridging molecular-level reaction mechanisms with system-scale sustainability metrics, this review positions high-valent metal AOPs as a promising approach for zero-waste water treatment within circular economies. Future frontiers, including bioinspired catalyst design, machine learning-guided optimization, and closed-loop reactor engineering, will bridge the gap between laboratory research to real-world applications.