Spent coffee-based activated carbon: specific surface features and their importance for H2S separation process.

Activated carbons were prepared from spent ground coffee. Zinc chloride was used as an activation agent. The obtained materials were used as a media for separation of hydrogen sulfide from air at ambient conditions. The materials were characterized using adsorption of nitrogen, elemental analysis, SEM, FTIR, and thermal analysis. Surface features of the carbons depend on the amount of an activation agent used. Even though the residual inorganic matter takes part in the H(2)S retention via salt formation, the porous surface of carbons governs the separation process. The chemical activation method chosen resulted in formation of large volume of pores with sizes between 10 and 30Å, optimal for water and hydrogen sulfide adsorption. Even though the activation process can be optimized/changed, the presence of nitrogen in the precursor (caffeine) is a significant asset of that specific organic waste. Nitrogen functional groups play a catalytic role in hydrogen sulfide oxidation.

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 NO(2) 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 NO(2) was reduced to NO and released from the system. In the case of virgin carbons, the NO(2) 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 NO(2) 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).