activated carbon

Activated carbon Activated carbon, also called activated charcoal, is a form of carbon commonly used to filter contaminants from water and air, among many other uses. It is processed (activated) to have small, low-volume pores that greatly increase the surface area available for adsorption or chemical reactions. (Adsorption, not to be confused with absorption, is a process where atoms or molecules adhere to a surface). The pores can be thought of as a microscopic "sponge" structure. Activation is analogous to making popcorn from dried corn kernels: popcorn is light, fluffy, and its kernels have a high surface-area-to-volume ratio. Activated is sometimes replaced by active.

Because it is so porous on a microscopic scale, activated carbon has a surface area of over 3,000 square metres per gram (920,000 square feet per ounce), as determined by gas absorption, and its porosity can run 10ML/day in terms of treated water per gram. Researchers at Cornell University synthesized an ultrahigh surface area activated carbon with a BET area of 4,800 m/g (1,500,000 sq ft/oz). This BET area value is the highest reported in the literature for activated carbon. For charcoal, the equivalent figure before activation is about 2–5 square metres per gram (610–1,530 sq ft/oz). A useful activation level may be obtained solely from the high surface area. Further chemical treatment often enhances adsorption properties.