Chemical structure of activated carbon

Activated carbon purification is primarily based on a phenomenon called adsorption, where molecules of a liquid or gas are trapped by either an external or internal surface of a solid. The phenomenon is somewhat similar to iron filings held by a magnet. Activated carbon has a very high internal surface area (up to 1500 m²/g), making itan ideal material for adsorption.

Activated carbon can be manufactured from a wide variety of raw materials containing a high percentage of carbon. The production process of converting the raw material into the finished adsorbent can be divided into chemical and thermal processes, both of which require the use of elevated temperatures.

The basic chemical structure of activated carbon is closely approximated by the structure of pure graphite. The graphite crystal is composed of layers of fused hexagons held by weak van de Waals forces. The layers are held by carbon–carbon bonds.

Activated carbon is a disorganised form of graphite, due to impurities and the method of preparation (activation process).

The pore structure developed in the activated carbon, and thus the final properties of the activated carbon, mainly depend on the raw material and the production process.