Activated carbon, also called activated charcoal, activated coal, or carbo activatus
Activated carbon is a form of carbon processed to be riddled with small, low-volume pores that increase the surface area available for adsorption or chemical reactions.Activated is sometimes substituted with active.
Due to its high degree of microporosity, just one gram of activated carbon has a surface area in excess of 500 m2, as determined by adsorption isotherms of carbon dioxide gas at room or 0.0 °C temperature. An activation level sufficient for useful application may be attained solely from high surface area; however, further chemical treatment often enhances adsorption properties.
Carefully selected raw materials are processed at low temperatures (200-300 C) to remove natural volatile components and residual moisture levels. This is the initial carbonisation step. This is followed by passing the carbonized raw material through high temperature (900-1000 C)activated retorts in the presence of a stringently controlled flow of steam which is used as the oxidizing medium. The resulting product is a power full adsorbent with a range of pores of molecular dimensions. Under a scanning electron microscope the pore development is clearly visible, appearig like a porous sponge. This high concentration of pores within a relatively small volume produces a material with a phenomenal internal surface area (800-1600 m2 g- BET N2). To put this into perspective, a tea spoon of activated carbon would exhibit a surface area equivalent to that of a football field. It is this vast internal surface area that gives activated carbon its unique abilityto adsorb a wide range of compounds for both the gas and liquid phase.
Activated carbons are complex products which are difficult to classify on the basis of their behaviour, surface characteristics and preparation methods. However, some broad classification is made for general purpose based on their physical characteristics.