Review of Mo-based materials in heterogeneous catalytic oxidation for wastewater purification

Recently, molybdenum (Mo) materials have been demonstrated as potential catalysts for advanced oxidation processes (AOPs) and attract increasing concentration due to the diverse valence states (Mo0, Mo2+, Mo3+, Mo4+, Mo5+, Mo6+). A comprehensive understanding of Mo catalysts for the AOPs dealt with wastewater purification and the generation mechanisms of reactive oxidant species (ROS) were little reported. This article reviews the latest progress on the common type and evolution of Mo-based materials used for AOPs including Mo0, molybdenum oxides, MoS2, Mo2C, MoP, metal molybdates and their derivatives. We summarize the intrinsic mechanisms and fundamental behaviors in the direct participation of Mo-based catalysts in AOPs and the auxiliary enhancement of AOPs by Mo-based co-catalysts. Furthermore, the possible obstacles, future directions, challenges and perspectives towards the actual wastewater treatment are discussed. This review could promote the development of Mo-based AOPs systems, and aid to choose the proper Mo-based AOPs system for the treatment of the practical industry.