Granular activated carbons have a relatively larger size of carbon particles in the granules compared to the carbon powders and consequently present smaller external surfaces. They are preferred for the adsorption of gases and vapors as the rates of diffusion are faster. The particle is a very important factor. It should not be too large size or the carbon too small to prevent excessive pressure drop along the bed & carrying away of the carbon particles with the gaseous stream. In fact, the size of the grain is chosen depending on the height of the bed to be used. The greater the height, the larger the size of the granules. They are used for water treatment and for decolorization & separation of components of the flow system. In liquid-phase applications, granular carbon is preferred because of following.

reasons:

• More efficient use of the adsorptive capacity of carbon can be obtained.
• Coloum treatment permits continuous operation & provides the flexibility necessary to cope with overloads and the blend effluents to maintain uniform quality.
• Granular carbons are available that can be thermally reactivated for reuse. Their use minimizes carbon consumption and eliminates the waste disposal problems associated with pulverized carbon.