Resource: Cameron Carbon Incorporated

The first known use of activated carbon dates back to the Ancient Egyptians who utilized its adsorbent properties for purifying oils and medicinal purposes.  Centuries later, the early ocean-going vessels stored drinking water in wooden barrels, the inside of which had been charred.  (However, by modern definition the carbon used in these applications could not truly be described as “activated”).  By the early 19th century both wood and bone charcoal was in large-scale use for the decolorization and purification of cane sugar.

Resource: Cameron Carbon Incorporated

Almost all materials containing a high fixed carbon content can potentially be activated. The most commonly used raw materials are coal (anthracite, bituminous and lignite), coconut shells, wood (both soft and hard), peat and petroleum based residues.

resource: Cameron Carbon Incorporated

In order to explain the capabilities of activated carbon an appreciation of its structure is most useful.

Much of the literature quotes a modified graphite-like structure; the modification resulting from the presence of microcrystallines, formed during the carbonization process, which during activation have their regular bonding, disrupted causing free valences which are very reactive. In addition, the presence of impurities and process conditions influence the formation of interior vacancies, in the microcrystalline structures.

Resource: Cameron Carbon Incorporated

Activated carbon can be considered as a material of phenomenal surface area made up of millions of pores ­rather like a “molecular sponge”.

The process by which such a surface concentrates fluid molecules by chemical and/or physical forces is known as ADSORPTION (whereas, ABSORPTION is a process whereby fluid molecules are taken up by a liquid or solid and distributed throughout that liquid or solid).

Resource: Cameron Carbon Incorporated

It has already been stated that essentially any carbonaceous material can potentially be activated.  In addition to the more common raw materials discussed earlier, others can include waste tires, phenol formaldehyde resin, rice husks, pulp mill residues, corn cobs, coffee beans and bones.

Resource: Cameron Carbon Incorporated

Because of the diverse end uses to which a carbon may be applied, it is difficult for manufacturers to conduct specific tests related to any one application.  A manufacturer can undertake some specialty tests after agreement with the user but this is the exception rather than the rule.  The size and number of pores essentially determine a carbon’s capacity in adsorbing a specific compound.  Since pore size and total pore volume determinations are quite lengthy, they are impractical as a means of quality control during manufacture. It is, therefore, necessary to relate the carbon’s surface capabilities to a standard reference molecule.

Resource: Cameron Carbon Incorporated

In almost every application of activated carbon the surface will eventually become saturated (or exhausted). This may occur within a few weeks, several months or many years depending on the conditions of service.