The effect of low-concentration SO2 on the adsorption of NO from gas over activated carbon

The effect of low-concentration SO2 on the adsorption of NO over activated carbon was studied using adsorption-desorption profiles obtained during thermal analysis-mass spectrometry. Using three different gas mixtures and adsorption temperatures between 293 and 413 K with NO and SO2 as the reactants, it was determined that NO2 and SO2 were the primary adsorbed species. The uptake of NO2 decreased with increasing temperature, whereas the uptake of SO2 was independent of temperature. Except at the highest adsorption temperatures, the amount of NO2 adsorbed was greater than that of SO2 adsorbed. The presence of SO2 inhibited adsorption of NO2, but the co-adsorption of NO2 promoted the adsorption of SO2. These data point to the possibility that the SO2 binding sites on the carbon are associated with the reaction NO + 1/2O(2) --> NO2, and to the different adsorption mechanisms which control NO2 and SO2 uptake. (C) 1997 Elsevier Science Ltd.