Interactions of NO2 with activated carbons modified with cerium, lanthanum and sodium chlorides

Highly porous wood-based activated carbon was impregnated with cerium, lanthanum and sodium chlorides using incipient impregnation method. On the samples prepared adsorption of NO2 was carried out from moist (70% humidity) air either with or without the prehumidification. The materials were characterized using adsorption of nitrogen, thermal analysis, FTIR, and potentiometric titration. The results indicated that for all materials a significant amount of NO2 was reduced to NO and released from the system. In the case of virgin carbons, the NO2 interacting with the surface along with nitric and nitrous acids formed there in the presence of water significantly increased the acidity of the carbons by the formation of oxygen-containing groups and organic nitrates. On the other hand, when chlorides were present the capacity to interact with nitrogen dioxide increased since the inorganic phase, depending on the nature of metal, bound NO2 in the forms of nitrates (Ce, La, Na), got oxidized/oxidized carbon surface (for Ce) or contributed to the formation of nitrosyl chloride (for Na). (C) 2008 Elsevier B.V. All rights reserved.