Activated carbon (AC) is a universal adsorbent. It is used to purify the water we drink, the air we breathe, many of the foods we eat and numerous industrial chemicals that we use every day. In drinking water treatment, activated carbon is used to remove taste and odor, VOCs and a myriad of unwanted organic materials. granular activated carbon (GAC) as a best available technology (BAT) to remove specific organics from drinking water. In home water filtration devices, it is also used to remove disinfectants such as chlorine and chloramines, as well as DBPs.
The three most common types of raw materials used to make activated carbon are coal, coconut shell and wood. Other types of raw materials are used to a much lesser extent, including fruit and olive pits, nut shells, bamboo and rice hulls. The most common types of activated carbon used for water treatment are coal-, coconut- and wood-based. Activated carbon can be used in powdered form (PAC), in granular form (GAC) or in pellet form, known as extruded activated carbon (EAC). Powdered activated carbon is dosed into the water and then filtered out. Granular activated carbon and, to a lesser extent, EAC, is used in fixed-bed-adsorber columns.
For small POU AC systems, such as faucet mounted and pitcher devices, 20 x 50 mesh size granular activated carbon is preferred. This small size provides fast kinetics for adsorption of impurities and chlorine removal, while maintaining an acceptable pressure drop. Larger POE systems use 12 x 30 or 12 x 40 mesh size. This larger particle size still allows for fast kinetics and an acceptable pressure drop, while more easily covering a large area. Both forms of GAC and EAC can be thermally reactivated after they are spent, whether for cost savings or for ecological benefits and waste minimization.