Efficient hydrogen sulfide adsorbents obtained by pyrolysis of sewage sludge derived fertilizer modified with spent mineral oil

Terrene, sewage sludge derived granulated fertilizer, was impregnated with spent mineral oil and then pyrolyzed at 600,800, and 950 degreesC. Materials obtained were characterized from the point of view of the pore structure and surface chemistry. Then the H2S breakthrough capacity was measured using a lab designed test. The results showed that the new adsorbents overperform by 30% materials obtained by simple thermal treatment of Terrene and by 230% virgin coconut shell based activated carbon. The surface reaction products were evaluated using thermal analysis. On the surface of new adsorbents hydrogen sulfide is oxidized mainly to elemental sulfur which is then deposited within the pore system. The breakthrough occurs when all small pores available to promote catalytic oxidation (caused by the inorganic sludge component) are filled with sulfur. An increase in pyrolysis temperature leads to an improvement in the performance of materials as hydrogen sulfide adsorbents. This is caused likely by changes in an inorganic phase and inorganic/carbonaceous phase interactions during pyrolysis.