In the simultaneous presence of NO and NO2, the NOx removal
mechanism depends both on the overall concentration and the
ratio of the two species. Thus, two mechanisms by which NOx
may be removed by wet scrubbing with alkaline solutions were
identified:
NO þ NO2¢N2O3 ð1Þ
N2O3 þ 2NaOH ! 2NaNO2 þ H2O
2NO2 þ 2NaOH ! 2NaNO2 þ NaNO3 þ H2O ð2Þ
The authors concluded that mechanism (1) predominates when
NO and NO2 are present in equal volumes, while mechanism (2)
occurs to a more limited extent. If NO2 is present in excess, it reacts
according to mechanism (2); while if the ratio by volume of NO to
NO2 is greater that one, the NO equal in volume to NO2 will react
with the NO2 (mechanism (1)), while the excess NO will remain
essentially unchanged.