Sewage sludge as a single precursor for development of composite adsorbents/catalysts

New York City origin sewage sludge was pyrolyzed and converted into adsorbents. Pyrolysis conditions were modified in order to evaluate the development of catalytic surface towards hydrogen sulfide oxidation. The holding time ranged from 0.5 h to 2 h and the final temperature was 650 °C, 800 °C and 950 °C. The resulting materials were characterized using adsorption of nitrogen (surface area and pore volume), thermal analysis, X-ray diffractions, XRF, SEM-EDX, TEM and pH measurements. On these materials adsorption/oxidation of hydrogen sulfide from moist air was carried out and the products of the surface oxidation were evaluated. The results indicated development of catalytic surface with an increase in pyrolysis temperature and holding time. As a result of solid state high temperature reactions between main components of sewage sludge, mainly iron, zinc, copper, phosphorus, silica and alumina, new mineral phases are formed which are very active in the oxidation process. Moreover, the presence of catalytic metals and organic vapors results in formation of carbon nanotubes on the surface of sewage sludge derived adsorbents as a result of self imposed chemical vapor deposition process.