Removal of hydrogen sulfide on composite sewage sludge-industrial sludge-based adsorbents

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.