Adsorption/oxidation of hydrogen sulfide on nitrogen-containing activated carbons

Wood-based activated carbon was modified by impregnation with urea and heat treatment at 450 and 950 degrees C. The chemical and physical properties o f materials were determined using acid/base titration, FTIR, thermal analys is, IGC, and sorption of nitrogen. The surface features were compared to th ose of a commercial urea-modified carbon. Then, the H2S breakthrough capaci ty tests were carried out, and the sorption capacity was evaluated. The res ults showed that urea-modified sorbents have a capacity similar to that of the received material; however, the conversion of hydrogen sulfide to a wat er-soluble species is significantly higher. It happens due to a high disper sion of basic nitrogen compounds in the small pores of carbons, where oxida tion of hydrogen sulfide ions to sulfur radicals followed by the creation o f sulfur oxides and sulfuric acid occurs. It is proposed that the process p roceeds gradually, from small pores to larger, and that the degree of micro porosity is an important factor.