Characteristics and application of iron-based materials in heterogeneous Fenton oxidation for wastewater treatment: a review

Advanced oxidation processes (AOPs) in wastewater treatment have a wide range of applications for the removal of refractory organics due to their ability to generate reactive, non-selective radicals. In the presence of catalysts, depending on the type of oxidant (H2O2, persulfate), AOPs often produce different radicals such as HO and SO4-, but the oxidation activity of deactivated catalysts is low. Iron-based materials have received a lot of attention due to their environmental friendliness and low cost, and their remarkable catalytic effect on heterogeneous AOPs. In this review, the activation and catalytic mechanisms of different iron-based materials (e.g., zero-valent iron, iron (hydr)oxides) in AOPs and the recent (last 10 years) progress in their application for the removal of (major) contaminants from water are highlighted. The catalytic performance of conventional iron-based catalysts can be improved by various modification strategies, such as controlling the microstructure, introducing support materials, constructing core-shell structures, and incorporating new metal-containing components. In addition, the conversion rate of Fe2+/Fe3+ during Fenton oxidation is an important factor affecting the catalytic ability, and some methods to improve the conversion rate such as light and addition of reducing agents have great potential. The overview of iron-based materials in AOPs helps researchers to select and develop more effective iron-based catalysts suitable for different AOP systems and shows that iron-based catalysts can be useful in large-scale practical applications.