The rates of single and simultaneous absorptions of dilute SO2 and NOin aqueous mixed solutions of NaClO2and NaOHwere measured at 25°C using a stirred vessel with a plain gas-liquid interface. In the SO2-NaClO2system, the absorption rate exceeded the gas-film controlled rate, which implies the possibility of gas-phase oxidation of SO2 due to the evolved C1O2. In the SO2-(NaClO2+NaOH) system, the absorption rate agreed with that under gas-film controlled conditions. In the (SO2+NO)-(NaClO2+NaOH)system, the reduction of the NO absorption rate in the presence of SO2 substantially exceeded that evaluated through the decrease in interfacial concentration of NaClO2and NaOHdue to surface reaction with coexisting SO2. The rate of absorption of SO2 exceeded the gas-film controlled rate. The decomposition of NaClO2proceeds to a greater degree during simultaneous absorption than the single absorption of SO2.

The absorption experiments of S02 and/or N02 diluted with nitrogen into aqueous solutions of sodium hydroxide and sodium sulfite were performed using an agitated vessel with a plane interface, with a view to developing a process for simultaneous removal of the major pollutants from stack gases. When S02 and N02 were simultaneously absorbed from an S02-N0x-N2 mixture, the rate of N02 absorption into aqueous NaOH solution was enhanced more than in the absence of S02, while for aqueous Na2S03 solution the rate was reduced. Such absorption behavior arises essentially from the change of sulfite concentration at the gas-liquid interface. Therefore the rate of N02 absorption with S02 could be predicted according to the mechanism with the competitive reactions of N02 with sulfite and water, which had been proposed in a previous study. The experimental results for both of the solutions were in reasonable agreement with the predictions.