Development of surface porosity and catalytic activity in metal sludge/waste oil derived adsorbents: Effect of heat treatment

New materials were prepared by pyrolysis of metal sludge from galvanization industry saturated with spent mineral oil. To evaluate the changes in the structural and chemical properties, the pyrolysis time and temperature varied. The materials were characterized using adsorption of nitrogen, FTIR, XRD, XRF, ICP, SEM and thermal analysis. Their catalytic activity was tested in the removal of hydrogen sulfide from simulated mixture of digester gas. The results indicated that a new carbon phase from the oil precursor not only provided microporosity but also contributed to the changes in surface chemistry of the materials, which are favorable for hydrogen sulfide oxidation to elemental sulfur. Based on surface chemistry analyses the catalytic centers consist of nitrogen-containing catalytic carbon and/or spinel-like structures containing iron, zinc and nickel. Longer carbonization time and higher temperature besides bringing more stability to the carbon phase via increasing its degree of aromatization and via rearrangement in nitrogen chemistry also impose favorable changes in an inorganic phase via solid-state reactions. (C) 2007 Elsevier B.V. All rights reserved.