Mechanisms of Active Substances in a Dielectric Barrier Discharge Reactor: Species Determination, Interaction Analysis, and Contribution to Chlorobenzene Removal

Abstract

Several typical active substances (^•NO, ^•NO₂, H₂O₂, O₃, ^•OH, and O₂^–•), directly or indirectly play dominant roles during dielectric barrier discharge (DBD) reaction. This study measured these active substances and removed them by using radical scavengers, such as catalase, superoxide dismutase, carboxy-PTIO (c-PTIO), tert-butanol (TBA), and MnO₂ in different reaction atmospheres (air, N₂, and O₂). The mechanism for chlorobenzene (CB) removal by plasma in air atmosphere was also investigated. The production of O═NOO^–• generated by ^•NO took around 75% of the total production of O═NOO^–•. Removing ^•NO increased the O₃ amount by about 80% likely because of the mutual inhibition between O₃ and reactive nitrogen species in or out of the discharge area. The quantitative comparison of ^•OH and H₂O₂ revealed that the formation of ^•OH was 3.06–4.65 times that of H₂O₂ in these reaction atmospheres. Calculation results showed that approximately 1.61% of H₂O was used for O₃ generation. Ionization patterns affected the form of solid deposits during the removal of CB in N₂ and O₂ atmospheres caused by Penning ionization and thermal radiation tendencies, respectively. Correlation analysis results suggested the macroscopic synergistic or inhibitory effects happened among these active substances. A zero-dimensional reaction kinetics model was adopted to analyze the reactions during the formation of active substances in DBD, and the results showed good consistency with experiments. The interactions of each active substance were clarified. Finally, a response surface method model was developed to predict CB removal by the DBD plasma process. Stepwise regression analysis results showed that CB removal was affected by the contents of different active substances in air, N₂ atmosphere, and O₂ atmosphere, respectively: O₂^–•, ^•OH, and O₃; H₂O₂, O═NOO^–•, and O₃; ^•OH and O₃.