Reduction of nitrite by sulfamic acid and sodium azide from aqueous solutions treated by gliding arc discharge

Nitrous and nitric acids form in aqueous solutions exposed to a gliding arc discharge burning in humid air. The anions interfere when the concentration of particular solutes such as pollutants must be determined. In particular they falsify the COD measurements and spectral investigations and thus the efficiency of the plasma treatment in pollutant abatement. The nitrite anions must be thus removed, which require specific reagents. The influence of parameters such as solution pH and [reducers]/[NO2−] ratio on the reduction reaction was evaluated. The reduction of nitrite into N2 either by sulfamic acid or sodium azide is a first-order pH-dependant reaction with regard to nitrite and reducers (k1 = 2.93 × 10−1 m3 kmol−1 s−1; k2 = 6.21 × 10−1 m3 kmol−1 s−1, respectively). Sodium azide is thus more reactive than sulfamic acid.