Behavior of N 2 and nitrogen oxides in plasma chemical processing of hazardous air pollutants

Plasma chemical behavior of N/sub 2/-O/sub 2/ mixed gases and nitrogen oxides such as N/sub 2/O, NO, and NO/sub 2/ was investigated to obtain baseline information on the generation of active oxygen species and the formation of inorganic byproducts in plasma chemical processing of hazardous air pollutants (HAPs). Ozone concentrations were too low even in air to oxidatively decompose 300/spl sim/1000 ppm of HAPs. The O/sub 2/ concentration in N/sub 2/-O/sub 2/ was the determining factor in the formation of all the nitrogen oxides. N/sub 2/O formation was enhanced with increase in O/sub 2/ concentration and in specific energy density, while a threshold value was observed around at 5% of O/sub 2/ concentration in the formation of NO and NO/sub 2/. N/sub 2/O decomposed in nonthermal plasma to give N/sub 2/ and O/sub 2/ and its decomposition efficiency was affected by its initial concentration and background O/sub 2/ concentration. N/sub 2/ and NO/sub 2/ are considered to be produced from NO, and N/sub 2/, N/sub 2/O, and NO could be produced from NO/sub 2/. Plasma chemical interactions between the nitrogen oxides and HAPs were not observed. HAPs and their fragments could be involved in the processes giving active oxygen species responsible for formation of the nitrogen oxides.