Absorption of NOx Induced by Sodium Chlorite Oxidation

Complete absorption of NO was achieved in aqueous solutions of alkaline NAClO2 at room temperature and atmospheric pressure. Experiments were conducted by bubbling various mixtures of NO, NO2 and O2, with the balance N2 into a liter of scrubbing solution. A greenish yellow color in the solution was observed after three minutes of operations. It is assumed that the color represented an intermediate, probably ClO2, active in the oxidation of NO. The mole ratio of the total amount of NO that flowed through the reactor to NaCl02 in the initial solution is 0.95 at breakthrough. The material balance, determined using ion chromatography showed that only anions in solution were NO3 and Cl. It should be noted that the pH of the scrubbing solution decreased rapidly from 10 to 12 to about 2. Consequently, the actual scrubbing was accomplished under acid conditions. Low concentrations of NaOH helped absorb NO, while high concentrations of NaOH inhibited the absorption. This is probably due to neutralization of the acid needed to promote the oxidation of NO with NaClO2. Current research is directed at determining the mass transfer coefficient as well as the effects of temperature and other flue gas components on the No absorption.