A critical review on ozone and co-species, generation and reaction mechanisms in plasma induced by dielectric barrier discharge technologies for wastewater remediation

Abstract

The development of cost-effective, feasible, and advanced wastewater treatment techniques remains critical to the availability and sustainability of scarce water resources. Advanced oxidation processes (AOPs) based on nonthermal plasma processes such as dielectric barrier discharges (DBDs) have recently been employed to combat biologically recalcitrant organic substances in water and wastewater streams. This is mostly due to their capability to generate in-situ UV light as well as numerous free radicals’ reactive oxygen species (ROS) such as ozone (O3), hydrogen peroxide (H2O2), atomic oxygen (O.), ozone radical ion (O3􀀀 ), hydroperoxyl radical (HO2), and superoxide anion (O2 􀀀 ) amongst others. OH., O3, and O2 . 􀀀 react directly or indirectly with complex organic pollutants in aqueous solutions while H2O2, O., O3􀀀 and HO2. mineralise organic toxins in water and in most cases act as the principal precursors for either OH., O3, or O2 . 􀀀 species during plasma treatment processes. This review primarily describes the principal reaction mechanism pathways of reactive oxygen species, and organic pollutants in DBD technologies. The pattern of RNS, methods for their quantification and the cause of their formation in DBD configurations have also been discussed. The outcomes of this review sustain that the optimisation of catalyst additives and critical parameters such as pH in DBD methods could efficiently promote the decomposition and mineralisation of water toxins. The review further highlights the superiority of double cylindrical DBD over single cylindrical and conventional DBD designs.