Activation of High-Valent Metal Oxidants on Carbon Catalysts: Mechanisms, Applications and Challenges

High-valent metal oxidants (HVMOs) have attracted considerable attention in advanced oxidation processes (AOPs) due to their high selectivity for oxidizing organic pollutants. However, the pursuit of green and efficient activators, together with the clarification of external factors affecting HVMO performance, remains a major challenge in practical applications. In this review, we present a comprehensive overview of the chemical properties of HVMOs, with a particular emphasis on their oxidation characteristics, focusing on permanganate (MnO4–), ferrate (FeO4–), dichromate (Cr2O72–). We further analyze energy changes and redox potential variations during the oxidation process. Recent advances in the activation of HVMOs by metal-free carbon materials are summarized, and the potential effects of common coexisting substances in environmental matrices, such as H+, OH–, inorganic anions, metal ions, and natural organic matter (NOM), are critically examined. Moreover, potential risks associated with residual HVMOs after organic pollutant oxidation are discussed, along with relevant separation and purification strategies. This review aims to deepen the understanding of HVMOs in environmental catalysis, explore their potential for resource recovery, and provide perspectives on future research directions and practical applications.