The sludge-based adsorbents were obtained either from mixtures of sewage sludge, waste oil sludge, and metal sludge or single components by carbonization at 650 °C in an inert atmosphere. The materials were used as media to remove hydrogen sulfide at room temperature in the presence of moisture. The initial and exhausted adsorbents after the breakthrough tests were characterized using sorption of nitrogen, thermal analysis, XRD, ICP, and surface pH measurements. Although on all materials hydrogen sulfide is oxidized to elemental sulfur, exceptionally good performance is obtained on the waste oil sludge-based adsorbent. This is attributed to the combined effects of surface chemistry and porosity. High pore volume of the waste oil sludge-based adsorbent provides space to store 30 wt % elemental sulfur formed when hydrogen sulfide undergoes oxidation on the surface. Mixing sludges and carbonization of their mixtures result in adsorbents whose capacity, although smaller than that for the single-component waste oil sludge-based adsorbent, is high compared to that of conventional activated carbons. Moreover, when additional chemical heterogeneity is provided, the structural and chemical features of the mixed waste oil sludge/sewage sludge-based adsorbents are enhanced as a result of synergy between the individual components, which occurs during solid-state reactions.

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Mixtures of sewage sludge, waste oil sludge, and metal oil sludge were prepared and carbonized at 950 degrees C in an inert atmosphere. Dynamic adsorption of H2S was measured on the materials obtained, and the breakthrough capacity was calculated. The initial and exhausted adsorbents after the breakthrough tests were characterized using sorption of nitrogen, thermal analysis, and XRF, XRD, and surface pH measurements. Mixing sludges leads to very high capacity adsorbents on which hydrogen sulfide is oxidized to elemental sulfur. Although the micropore volume of the adsorbents obtained is not high, their high volume of mesopores contributes significantly to reactive adsorption and provides space to store the oxidation products. The H2S breakthrough capacity on the new materials reaches 10 wt %. These adsorbents work until all active pores are filled and the catalytic centers are exhausted. The reason for such high capacity is in the formation of catalytically active mineral like phases during pyrolysis in the presence of nitrogen and carbon. This highly dispersed phase provides basicity and catalytic centers for hydrogen sulfide dissociation and its oxidation to sulfur.