There is evidence that in the Ancient Egypt the activated charcoal was thought to have medicinal properties. The hindus also used it to filter the water and in the XIIIth century the carbon was used in the sugar purification. Activated coal may be defined as porous material with a large superficial area capable of adsorbing substances. The raw material common in its production are:

• bituminous carbons
• bones
• coconut shell
• babaçu shell
• lignite
• turf
• nut shell
• sugar
• wood
• olive stone
• peach stone
• oil residues

The carbon can be activated by two different processes: by steam activation and by chemical treatment. The activated carbon composition is basically carbon, except for a maximum amount of 20% of minerals that are indicated and can be found in the ash content.

The activated carbon adsorption process depends on the available superficial area. It envolves a solid-liquid interface, as to the of aqueous solutions treatment, and gas-solid interface, as to the of gas treatment. The adsorption may happen through two ways:

• i) fisiossorptions – the molecules are adsorbed by the van der Waals forces (multilayers adsorption).
• ii) quimiossorptions – it happens a chemical reactions between the adsorbato and the adsorvente.

Often the products for sale have a superficial area among 500 – 1500 m2/g. The activated carbon can be characterized according to the following porous volumes:

• Macroporous – diameter larger than 50nm
• Mesoporous – diameter among 2 – 50nm
• Microporous – less than 2 nm of diameter.

Adsorption studies of particular substances like iodine, methylene blue and phenol can give us a good measurement of the activated carbon superficial area.

Picture 1: Conceptions of the porosity effects of the activated carbon. (click here to enlarge the image)

There are three basic activated carbon forms: powdered, granular and pelletized. Generally, the powdered form is useful  for color treatment; the granular form for water treatement and the pelletized form for gas application and catalysis. However, this is not a rule, for instance, in the Brazilian market the powdered activated carbon is often used to remove taste and odor in the drinking water treatment. Some Brazilians companies like SABESP, SANASA and CORSAN and others utilize this process.

Industries that demand additional purification of drinking water treatment process make use of the activated carbon filter to remove chlorine.

Picture 2: Basic forms of activated carbon: (A) peletized (B) powdered (C) granular (click here to enlarge the image)

Activated carbons with low ash content are offered to specifics industries, like the pharmaceutical. A special treatment is used to make these products. Some goals of activated carbon utility are: impurity removal, solvent vapor removal, air separation, CO2 removal, fuel gases removal, solvent recovery, toxics substances removal.

Other application is in the refrigerators deodorization and in the removal of strong odors, included hygienical purposes. In some cigarettes filters its function is to decrease the tar and the nicotine concentration.