Investigation of SO_2 and NO adsorption species on activated carbon and the mechanism of NO promotion effect on SO_2

摘要

Activated carbon (AC) is notably effective for SO_2 and NO removal. SO_2 and NO adsorption species like oxided state SO_2, SO_3 and C-O-NO are analyzed, and the desorption energies for each species were calculated in this work. The desorption energies of SO_2 adsorption species are 92.89 kJ/mol for strongly adsorbed SO_2 or SO_3 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 C-O-NO and 118.88 kJ/mol for nitrate. The changes of the SO_2 and NO adsorption amounts and species were investigated under different atmospheres. The results show that the SO_2 adsorption amount triples when there are both NO and H_2O, whereas the NO adsorption amount decreases by 93%. When NO is added, the amount of the two SO_2 adsorption species are both increased, whereas part of the pre-adsorbed SO_2 is desorbed by NO added afterwards; the amounts of both NO adsorption species are greatly decreased when SO_2 is added, whereas the pre-adsorbed SO_2 increases the amount of physically adsorbed NO. The changes of the adsorption of AC oxygen groups after different atmospheres are observed in the CO_2, CO and H_2O profiles using the TPD-MS methods. The NO adsorption-desorption process increased the number of C=O groups on AC with more activated sites provided for SO_2 oxidation. C-O-NO is verified as the main product among the first NO adsorption species, and the SO_2 replacement of C-O-NO promotes SO_2 adsorption.