A novel double dielectric barrier discharge reactor for toluene abatement: Role of different discharge zones and reactive species

Abstract

A coaxial cylindrical double dielectric barrier discharge (DDBD) reactor with two separate discharge zone was designed and the role of its different discharge zones and reactive species were explored in toluene degradation. The inner tube (the space between the high voltage electrode and the inner barrier) had a higher gas temperature and reactive species concentration due to its stronger discharge intensity compared with the outer tube (the space between the inner and outer barriers). The two discharge zones exhibited similar toluene removal efficiency, whereas the mineralization rate of the inner tube exceeded that of the outer tube under 18–22 kV, and the result was opposite under 24–28 kV. The gas-flow direction had no significant effect on the toluene removal efficiency, but the mineralization rate of the down-flow reactor (23.7%–54.4%) exceeded that of the reverse-flow reactor (20.7%–45.5%). The inner and outer tubes mainly responsible for the initial degradation and further oxidation of toluene, respectively. The role of long-lived (N2(A3∑u+) and metastable O2 (a1Δg and b1Σg+)) and short-lived (N2(C3∏u), N2(B3∏g), and atomic O (1D and 3P)) reactive species on toluene degradation and oxidation was analyzed. The plausible toluene degradation mechanism in the DDBD reactor was proposed based on the role of different discharge zones and reactive species. The finding herein is significant in the design, optimization and application of DBD reactors.