Investigation of SO2 and NO adsorption species on activated carbon and the mechanism of NO promotion effect on SO2

Activated carbon (AC) is notably effective for SO2 and NO removal. SO2 and NO adsorption species like oxided state SO2, SO3 and CONO are analyzed, and the desorption energies for each species were calculated in this work. The desorption energies of SO2 adsorption species are 92.89 kJ/mol for strongly adsorbed SO2 or SO3 and 256.28 kJ/mol for sulfate. The desorption energies of NO adsorption species are 67.56 kJ/mol for physically adsorbed NO, (NO)2 dimers or CONO and 118.88 kJ/mol for nitrate. The changes of the SO2 and NO adsorption amounts and species were investigated under different atmospheres. The results show that the SO2 adsorption amount triples when there are both NO and H2O, whereas the NO adsorption amount decreases by 93%. When NO is added, the amount of the two SO2 adsorption species are both increased, whereas part of the pre-adsorbed SO2 is desorbed by NO added afterwards; the amounts of both NO adsorption species are greatly decreased when SO2 is added, whereas the pre-adsorbed SO2 increases the amount of physically adsorbed NO. The changes of the adsorption of AC oxygen groups after different atmospheres are observed in the CO2, CO and H2O profiles using the TPD-MS methods. The NO adsorption-desorption process increased the number of CO groups on AC with more activated sites provided for SO2 oxidation. CONO is verified as the main product among the first NO adsorption species, and the SO2 replacement of CONO promotes SO2 adsorption.