ABSTRACT
Activated carbons are manufactured from a wide variety of carbonaceous materials, including sawdust and wood, peat, lignite, coal and petroleum coke, bone, coconut shells, and sugar. These substances are first converted to char by a carbonization process in which the raw material is slowly heated in the absence of air to temperatures up to 600°C in order to drive off volatiles and to increase the carbon content of the base material. Several potential mechanisms have been suggested to account for the observed ability of activated carbon to remove dissolved metals from aqueous solution. These include: cation exchange by the acidic surface oxides; chemisorption; precipitation of insoluble metal species within the carbon pores from an otherwise undersaturated bulk solution, the carbon surface serving as a nucleating agent. These also include: adsorption of metals bound to organics in the water as organometallic complexes; and chemical reduction of highly soluble, oxidized metal species to less soluble reduced forms.
