The use of activated carbon to treat water was known over 2000 years ago. Beginning in the 20th century, it was produced commercially in a powdered form. Activated carbon was initially used to decolorize sugar and for water treatment to remove taste and odor. During World War I, granular activated carbons were further developed for gas masks and subsequently for water treatment, solvent recovery, and air purification. Due to activated carbon’s unique structure, a very large surface area is available. Activated carbon can be produced from a variety of carbonaceous raw material including bituminous coal, sub-bituminous coal, lignite coal, coconut shells, wood, and other cellulosic materials. The raw material precursor is a primary driver of the intrinsic properties of the activated carbon. Production method is another primary driver of the intrinsic properties of the activated carbon. Post production methods further enhance activated carbon adsorption performance for specific applications.
Surface areas ranging from 450–1400 square meters per gram are created in the activated carbon. Activated carbon has two primary types of pores and these are macropores (>.1 µm) and micropores (.001 to .1 µm). The macropores serve as transport pores to the carbon’s interior and interconnect with the micropores. The micropores are responsible for the vast majority of the internal surface area of the of activated carbon particles and are the primary adsorption mechanism. Surface area and pore volume are the main parameters relevant to the performance of the activated carbon. It is the pore volume and size that determines the type and size of the molecules that can be adsorbed. The surface area determines to large extent the volume of adsorbate that can be adsorbed with the activated carbon.