Absorption of Nitrogen Oxides in Aqueous Sodium Sulfite and Bisulfite Solutions

Abstract

Absorption experiments of NO and N02 diluted with nitrogen (NO* concentrations over a few hundred ppm) in aqueous solutions of sodium sulfite and/or bisulfite were performed at 25 °C using the agitated vessels with gas dispersion and with a plane interface. The experimental results were discussed based on the film theory of gas absorption accompanied by fast, pseudo mth order chemical reaction. The reaction between NO and S032was found to be second order with respect to NO and zero order with respect to S032-, and the rate of absorption of NO into the sulfite solution increased as the concentration of N02 in the gas phase increased. As for the absorption of N02 in the sulfite solution, it was found that the absorption rates went through a maximum as the sulfite concentration varied, and the reaction mechanism to absorption was with competitive reactions involving the hydrolysis of N02 and the reaction between N02 and S032-in the liquid film. The reduction of N02 was found to be first order with respect to S032-and first order with respect to N02, and so the value of the second-order rate constant was evaluated, while for the hydrolysis of N02 the reaction order was second order with respect to N02. Also the absorption of N02 into the bisulfite solution was accompanied by competitive reactions as well as in the sulfite solution. In addition, aqueous solutions with various reducing or oxidizing agents were examined for the absorption of N02. Furthermore, the effect of temperature on the absorption of N02 in the sulfite solution was studied at 10, 15, and 25 °C.

Nitrogen Dioxide Absorption and Sulfite Oxidation in Aqueous Sulfite

“…This trend was also observed by Takeuchi et al (5). This trend was also observed by Takeuchi et al (5).…”

“…Rg,exp × 10 6 (mol/(cm 2 s atm)) Rg,mod/Rg,exp Nox × 10 8 (mol/(cm 2 s)) Nox,mod/Nox,exp additive (mM) 5 (23) reported a value of 4 for the above ratio at 50°C. Figure 3 gives the calculated rate of sulfite oxidation as a function of thiosulfate.…”

“…Takeuchi et al (5) measured NO2 absorption into aqueous sodium sulfite and bisulfite solutions, both in a gas liquid contactor and a spray column, and they have reported the reaction rate constant for the above reaction at 25°C. Although previous investigators have studied NO2 reaction with sulfite, these studies were usually performed under conditions far from that of a limestone slurry scrubber.…”

MnOx/TiO2 composite nanoxides synthesized by deposition-precipitation method as a superior catalyst for NO oxidation

“…And this conclusion inspired Kang et al to develop a high-performance two-stage catalyst system for SCR of NO x with the pre-oxidation of NO during the first stage [5]. For wet scrubbing method, the solubility and reactivity of NO x could also be improved significantly when NO is partially or completely converted to NO 2 [6,7]. Therefore, much effort has been focused on developing eligible catalysts for NO oxidation [8][9][10][11][12][13][14][15].…”

Photocatalytic oxidation of nitric oxide with immobilized titanium dioxide films synthesized by hydrothermal method

“…Traditional wet processes are very efficient to remove NO 2 from flue gas, but cannot remove NO because of its low solubility in aqueous solution [7][8][9][10]. One promising approach to improve the absorption efficiency of wet processes is the transformation of NO to NO 2 by the gas-phase oxidation.…”