Adsorption of Heavy Metals on Coal-Based Activated Carbons

Abstract

Zinc chloride-activated and steam-activated carbons were prepared from Maghara coal (Sinai, Egypt). The surface properties of these carbons were determined from nitrogen adsorption isotherm studies at 77 K and of carbon dioxide at 298 K. The adsorption of Methylene Blue from aqueous solution at 308 K was also investigated. The removal of heavy metals (Hg2+, Cd2+ and Pb2+) from aqueous solution was investigated at pH < 7.0 and at 308 K. The prepared activated carbons exhibited high adsorption capacities for Methylene Blue. The maximum capacity amounted to 83 mg dye per g of carbon, which is equivalent to a surface area of 500 m2/g. The capacity for the removal of heavy metals from their aqueous solutions depends on the pH and the extent of activation, i.e., on the amount of zinc chloride used for chemical activation or on the percentage burn-off during physical activation with steam.