Enhancing iron redox cycling for promoting heterogeneous Fenton performance: A review

Conventional water treatment methods are difficult to remove stubborn pollutants emerging from surface water. Advanced oxidation processes (AOPs) can achieve a higher level of mineralization of stubborn pollutants. In recent years, the Fenton process for the degradation of pollutants as one of the most efficient ways has received more and more attention. While homogeneous catalysis is easy to produce sludge and the catalyst cannot be cycled. In contrast, heterogeneous Fenton-like reaction can get over these drawbacks and be used in a wider range. However, the reduction of Fe (III) to Fe(II) by hydrogen peroxide (H2O2) is still the speed limit step when generating reactive oxygen species (ROS) in heterogeneous Fenton system, which restricts the efficiency of the catalyst to degrade pollutants. Based on previous research, this article reviews the strategies to improve the iron redox cycle in heterogeneous Fenton system catalyzed by iron materials. Including introducing semiconductor, the modification with other elements, the application of carbon materials as carriers, the introduction of metal sulfides as co-catalysts, and the direct reduction with reducing substances. In addition, we also pay special attention to the influence of the inherent properties of iron materials on accelerating the iron redox cycle. We look forward that the strategy outlined in this article can provide readers with inspiration for constructing an efficient heterogeneous Fenton system.