Sewage sludge-derived materials were used as adsorbents of hydrogen sulfide from moist air. The adsorbent obtained by carbonization at 950 degrees C has a capacity twice of that of coconut-shell-based activated carbon. The capacity of the sludge-derived materials increases with increasing carbonization temperature. It is likelythatduring carbonization at 950 degrees C a mineral-like phase is formed that consists of such catalytically active metals as iron, zinc, and copper. The results obtained demonstrate that the presence of iron oxide significantly increases the capacity of commercial carbon and activated alumina. The sludge-derived adsorbents are efficient for hydrogen sulfide removal until the pore entrances are blocked with sulfur as the product of oxidation reaction. For materials in which the catalytic effect is predominant, hydrogen sulfide is adsorbed until all pores are filled with sulfur. There is also indication that chemisorption plays a significant role in the removal of hydrogen sulfide from moist air.

Activated carbons of different origins were studied as methyl mercaptan adsorbents in wet, dry, and oxidizing conditions. The materials were characterized using adsorption of nitrogen, Boehm titration, and thermal analysis. Investigation was focused on the feasibility of the removal of methyl mercaptan on activated carbons and on the role of surface chemistry and porosity in the adsorption/oxidation processes. The results showed relatively high capacities of carbons for removal of CH3SH. The amount adsorbed depends on the surface features. Methyl mercaptan, in general, is oxidized to disulfides, which, depending on the chemistry of the carbon surface, can be converted to sulfonic acid due to the presence of water and active radicals.

Activated carbons of different origins were studied as sulfur dioxide adsorbents. The materials were characterized using adsorption of nitrogen, titration, X-ray photoelectron spectroscopy, and thermal analysis. The investigation was focused on the role of nitrogen functionality and pore sizes in the process of SO2 adsorption/oxidation. The results showed that quaternary and pyridinic type nitrogen significantly enhance the adsorption capacity. It happens when catalytic centers are located in the small pores, which is likely to help in achieving high dispersion of these centers. Besides an oxidation effect due to the formation of active oxygen radicals, the nitrogen-containing centers attract the SO4 2ions causing the gradual pore filling which is the most effective usage of the carbon pore space.

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Activated carbons of different origins were impregnated with urea and heat-treated at 450 and 950 °C. Surface properties of adsorbents were evaluated using nitrogen adsorption, potentiometric titration, Boehm titration, elemental analysis, and thermal analysis. Then, the CH3SH breakthrough capacity tests were carried out and the adsorption capacities were evaluated. The results showed that the amount adsorbed depends strongly on the modification conditions of the carbon surface. It increased from 1.4 to 10 times after introduction of nitrogen species. Immobilization of methyl mercaptan on the surface is likely governed by the redox process, and basic nitrogen groups can act as catalysts for electron transfer from sulfur to oxygen. Dimethyl disulfide and methyl methanethiosulfonate are the main products of methyl mercaptan oxidation.

Activated carbons of different origins were studied as methyl mercaptan adsorbents in wet conditions. To broaden the spectrum of surface acidity, carbons were oxidized with hydrogen peroxide. The surface properties of adsorbents were evaluated using nitrogen adsorption, Boehm titration, potentiometric titration, and thermal analysis. The study was focused on the role of surface chemistry and porosity in the adsorption/oxidation of methyl mercaptan. The results showed that the amount adsorbed depends on the surface features. Although the main product of methyl mercaptan oxidation is dimethyl disulfide, in some cases, oxidation proceeds further, likely leading to the formation of methyl methanethiosulfonate as detected using GC/MS.