Mesoporous carbons from waste tire char and their application in wastewater discoloration

Waste tire char was employed as the precursor for the production of activated carbons with steam activation. Carbons with different porosities were obtained by activating the char to different extents of burn-off. Unlike commercial grade carbons that are generally microporous, the pores of the tire-char carbons are mainly composed of mesopores that have a mean size of 500 Angstrom. Both the surface area and pore volume of the carbons increase with the extent of activation and pass through a maximum at a burn-off of 43% above which the porosity decreases with further activation. Adsorption of methylene blue from aqueous solutions shows a monolayer coverage of the adsorbate on the carbon surface and a full access of the adsorbate to all the pores, which renders a high discoloration capability per unit area of the carbons, The methylene blue capacity of the carbons was found to increase with the adsorption temperature. Langmuir analysis shows that this increase in capacity with temperature can be attributed to an increase in the number of the adsorption sites as well as the endothermic nature of this specific adsorption. (C) 2002 Elsevier Science Inc. All rights reserved.