Adsorption of Hydrogen Sulfide on Activated Carbon

Abstract

Adsorption-desorption isotherms of hydrogen sulfide on activated carbon were obtained by a gravimetric method at 20°, 30°, and 40° in order to elucidate the mechanism of adsorption. Hysteresis loops of the isotherms were observed and it was confirmed that only extremely small amounts of hydrogen sulfide were chemisorbed. The Dubinin-Astakhov equation could be applied to these adsorption isotherms of hydrogen sulfide (E=2580-2748, n=2). Isosteric heats of adsorption of hydrogen sulfide on activated carbon Nos. 2 and 3 in the range of W/W₀ 0.07-0.6 were less than twice the value of the heat of condensation (ΔH₀=4.43 kcal/mol) and that of activated carbon No. 4 was more than twice the value of the heat of condensation. It was observed that activated carbon Nos. 2-4 consisted mainly of micropores smaller in radius than 15Å. These results suggest that adsorption of hydrogen sulfide in micropores of activated carbon resulted in volume filling, that hydrogen sulfide was mainly physisorbed, and that high isosteric heat of adsorption in some cases, such as No. 4, was not attributable to chemisorption, but to the small size of the micropores.