Role of Sulfite Oxidation in NO₂ Absorption in a pH-Neutral Scrubber Solution

Nitrogen dioxide (NO2) absorption in aqueous sulfite solutions has recently gained more attention to reduce NOx emissions. The NO2 removal efficiency is strongly influenced by the competing reactions of and oxidation. present study investigates role oxidation at neutral pH. effects concentration, thiosulfate, pH, inlet oxygen concentration on efficiency, rates were investigated under well-controlled conditions 25 °C a laboratory-scale wet scrubbing system. showed strong dependence increased linearly with increasing concentrations between 150 ppm. At highest 20 mM, was around 80%. Oxidation during presence 5 vol % O2 solution ranged from mg·L–1·min–1 1 mM 200 sulfite. rate decreased significantly when thiosulfate added, while independent 2–10 O2. decreasing pH 6 8 proportionally as predicted sulfite–bisulfite equilibrium. implication these results that less feeding needed industrial if can be maintained instead lower such simultaneous SO2 scrubbing.