Nitric oxide scavenging of hydroxyl radicals in a nanosecond pulsed plasma discharge gas–liquid reactor

Abstract

A continuous gas–liquid film flow reactor with a nanosecond power supply was utilized to produce , , and NO2 from Ar/NO mixtures (gas phase) and deionized water (liquid phase). High concentrations of added NO were used as an ·OH scavenger and to provide insight into the reaction pathways. Chemical analysis of the products exiting the reactor was performed by quenching the liquid samples to eliminate the post-plasma reactions. The gas phase products were analyzed using FTIR and the liquid phase samples were analyzed using ion chromatography and UV–vis spectrophotometer. The concentrations of , and NO2 increased with increasing inlet concentrations of NO while the concentration of H2O2 decreased moderately. The plasma gas temperature was approximately 565 K and was unaffected by the NO feed concentration, while the electron density varied from 4.83 × 1016 cm−3 to 1.16 × 1017 cm−3 for inlet NO concentrations of 0 ppm to 20 000 ppm, respectively. The increase in NO2 concentration in the gas phase suggests that ·OH provides a source of atomic oxygen (O). The results also suggest that ·OH plays an important role in the formation of HNO2 and HNO3 by directly reacting with NO and NO2, respectively. The highest production rate of ·OH was 6.5 × 10−6 moles s−1 at 20 000 ppm inlet NO. The energy yield of ·OH was 5.7 × 10−7 moles J−1 at 20 000 ppm inlet NO and is in agreement with our previous work and other literature reports.