Emerging investigator series: could the superoxide radical be implemented in decontamination processes?

Abstract

The superoxide radical (O₂˙⁻) is an important reactive oxygen species (ROS) in diverse natural aquatic systems and engineered water treatment processes. The increasing recognition of its thermodynamic and kinetic properties predisposes one to ask the thought-provoking question: could O₂˙⁻ be produced in engineered systems as key species and utilized in wastewater and groundwater remediation? In this perspective, we elaborate on the unique physicochemical characteristics of O₂˙⁻ in various aquatic systems, followed by the relative importance of different sinks for the decay of O₂˙⁻. Then, a thorough discussion on the role of O₂˙⁻ in decontamination systems, such as heterogeneous Fenton and photocatalysis, is brought out. Finally, we emphasize the challenges that we are facing ahead (e.g., lack of solid kinetic reactivity data and unclear synergistic mechanisms with other ROS). We believe that environmental implications of superoxide chemistry deserve a more thorough discussion in the water engineering communities, and we hope that this perspective motivates researchers in the field of water quality and treatment for further exploration of this exciting area.