The influence of relative humidity on double dielectric barrier discharge plasma for chlorobenzene removal

Abstract

The influence of relative humidity on the electrical characteristics, the generation of the active species and the chlorobenzene removal performance was studied. The results show that both the peak-to-peak current and the discharge power decreased with the increase of relative humidity under the same peak-to-peak voltage. A reduction of electron temperature was observed with the addition of water vapour, affecting the electron impact processes. It was observed that excited states of N 2 and O were affected by the water due to the quenching effect. A decrease of chlorobenzene removal efficiency was achieved from 81.7% to 70.7% as the increase of humidity. However, carbon balance analysis depicts the yields of CO 2 in humid air were higher than that in dry air due to the help of radical OH, especially in RH = 40%, and highest energy efficiency with 4.4 g kW −1 h −1 was also achieved at RH = 40%. Chlorine balance indicates that the product HCl is more easily generated in the presence of H 2 O. A difference in the chlorobenzene degradation pathway was revealed. Fewer kinds of benzenoid byproducts were found in dry air, which was in agreement with the plasma diagnostics results. Radicals generated in humid air promoted the total oxidation process, resulting in fewer kinds of ring-open byproducts and higher CO 2 yield. • A novel home-made mini dDBD reactor was used to remove chlorobenzene. • Active species generated in the discharge were affected by relative humidity. • The addition of water was helpful to improve the yield of CO 2 and the yield of HCl. • The removal pathways of chlorobenzene were affected by the water.