Decomposition of benzene vapour using non-thermal plasmas: The effect of moisture content on eliminating solid residue

This study investigated the effect of power, carrier gases and moisture content on the removal of benzene in dry air and humidified air in a DBD plasma reactor. The influence of plasma power, carrier gases and humidity on benzene conversion and product selectivity were explored. The main decomposition products were CO, CO2, lower hydrocarbons (C-1-C-5) and solid residue in the reactor. This study reveals that benzene removal efficiency and the selectivity to CO2 increased with power in both dry and humidified air. In contrast, the selectivity to lower hydrocarbons decreased. The most important finding of this study was that the formation of solid residue in the plasma reactor can be removed in humidified air. As the amount of water vapour increased from 0% to 35% at 20 degrees C, the benzene removal efficiency and CO2 selectivity increased; O-3 decreased from 7.3 ppm to 0.5 ppm; NOx and solid residue were eliminated. These effects are probably due to OH radicals, and the mechanism for the various effects are proposed. The maximum benzene removal efficiency observed was 93.7%, and the maximum selectivity to CO2 was 82.4% (both at a relative humidity of 35% at 20 degrees C and 10 W). This study demonstrated that plasma-assisted benzene remediation operating in a humid condition can overcome the major drawback of plasma-assisted VOC conversion in the air by eliminating the solid residues in the reactor.