Activated Carbon Systems for Removal of Light Gasesa

Effect of Surface Characteristics of Wood-Based Activated Carbons on Adsorption of Hydrogen Sulfide

“…As proposed by Hedding and Rao (10), at the virgin carbon surface, dissociation of hydrogen sulfide occurs in the film of adsorbed water and then hydrogen sulfide ions, HS Ϫ , are oxidized by oxygen radicals to elemental sulfur. On the other hand, when caustic is present, it catalyzes oxidation to elemental sulfur until all base is exhausted (4).…”

“…It is well known that interactions of molecules with the surface of any sorbent and thus their immobilization in its pores depend on the chemical nature of materials (3). Therefore for the removal of acidic gases carbons impregnated with caustics are used (4,5), whereas impregnation with acids helps to immobilize basic species. In the cases where oxidationreduction reaction is predominant, the surface of activated carbons is impregnated with active species such as, for instance, potassium iodide, potassium permanganate, or urea (6).…”

“…Although the removal of odorous H 2 S from off-stream gases is very effective, those carbons have a very low self-ignition temperature (7) and can ignite spontaneously. Another disadvantage of caustic carbons is the oxidation of hydrogen sulfide to elemental sulfur (4,5), which cannot be removed from carbons by washing with water. Moreover, the activity of caustic carbons toward H 2 S oxidation ends when the caustic is consumed and the carbon pores are blocked by sulfur and sodium or potassium salts (4).…”

Effect of pH and Surface Chemistry on the Mechanism of H2S Removal by Activated Carbons

“…For instance, carbons impregnated with noble metals or with transition metal oxides can catalyze the air oxidation of VOCs. Activated carbon can be impregnated with caustics in order to increase its capacity for acidic gases (8,9). Another treatment is impregnation of carbons with certain nitrogen compounds such as urea and then calcination at high temperature (10), which builds basic nitrogen compounds into an activated carbon matrix.…”

Initial Heats of H2S Adsorption on Activated Carbons: Effect of Surface Features

“…Activated carbons are used as adsorbents of hydrogen sulfide and as catalysts for its oxidation (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). It was demonstrated in the literature that at temperatures higher than 473 K the catalytic influence of the carbon surface is enhanced due to the presence of sulfur, which is the product of the oxidation reaction (8).…”