Generation of Nitric Acid and Nitrous Acid in Distilled Water Irradiated with Atmospheric-Pressure Plasma Jet

摘要

An atmospheric-pressure argon (Ar) plasma jet was directly irradiated onto distilled water. Semiquantitative determination using test strips and flow injection analysis (FIA) revealed that nitric acid (HNO3) and nitrous acid (HNO2) were generated in distilled water by plasma jet irradiation for 1 min. The nitrate ion (NO3- ) and nitrite ion (NO2- ) concentrations in distilled water irradiated with a plasma jet, determined from the test strips,were in good agreement with those determined by FIA. The NO3- concentration in distilled water proportionally increased with the plasma irradiation time, whereas the NO2- concentration was almost unchanged. It is considered that high-energy electrons in the plasma jet collided with nitrogen molecules (N2) and oxygen molecules (O2) to generate nitrogen (N) and oxygen (O) radicals. Nitrogen oxide (NxOy) generated upon the reaction of the radicals is considered to react with water molecules (H2O) in air and at the surface of distilled water to generate HNO3 and HNO2. [DOI: 10.1380/ejssnt.2014.410]