Revisiting Fenton Chemistry: From Classical Systems to Advanced Materials Design, Mechanisms, and Future Directions in Wastewater Treatment

The Fenton reaction remains one of the most widely investigated advanced oxidation processes for wastewater treatment due to its ability to generate highly reactive oxygen species capable of degrading persistent organic pollutants. However, classical homogeneous Fenton systems suffer from significant limitations, including narrow pH applicability, iron sludge generation, and poor catalyst reusability. In response, extensive research has focused on the development of heterogeneous and advanced Fenton-like catalysts aimed at overcoming these challenges while enhancing catalytic efficiency and operational stability. This review provides a comprehensive and critical analysis of the evolution of Fenton catalysis, from classical homogeneous systems to advanced materials, including nanostructured catalysts, carbon-based Fe–N–C systems, metal–organic frameworks, and single-atom catalysts. A unified evaluation framework is proposed, integrating key performance parameters such as catalytic activity, manufacturability, stability, and catalyst lifespan. Comparative analysis reveals that improvements in activity are often accompanied by trade-offs in cost and scalability, indicating that the most advanced materials do not necessarily provide the best practical performance. A life cycle-oriented perspective is incorporated, emphasizing catalyst reuse, lifespan, and iron leaching, and providing quantitative insight into cumulative catalytic performance. The results demonstrate that long-term efficiency is governed not only by intrinsic activity but also by durability and operational stability under realistic conditions. Finally, current challenges and future directions are discussed, including scalable synthesis, improved mechanistic understanding, and integration into hybrid treatment systems. This review bridges the gap between fundamental research and practical application by highlighting the importance of balancing performance, stability, and sustainability in the design of next-generation Fenton catalysts.