Activated carbon is a form of carbon that has been manufactured to have a complex phase of graphite like crystallites with a porous structure consisting of micro pores (2nm or less), meso (between 2-50nm) and macro pores (larger than 50 nm). These porous structures provide a large surface where adsorption of unwanted organic compounds can be carried out. Common activated carbon have surface areas of 800 to 1500 m2/gm. Differences in pore sizes affects the adsorption capacity for molecules of different spatial shapes and sizes.

Activated carbon are made from materials with a carbon content like coal, wood, coconut shells, palm kernel shells. These are pyrolysis at high temperatures in the absence of air to create sinuous caves of surfaces for adsorption. The carbonized material is then activated by exposing them to oxidizing agents like carbon dioxide, oxygen or steam again at high temperatures.