Activated carbon is a highly absorbent charcoal with the remarkable property of being able to selectively absorb various materials from mixtures. During activation, the natural internal surface area of the raw material, consisting of a myriad of microscopic and sub microscopic pores, is enlarged, there by enhancing the absorption of certain materials by attracting molecules from the surrounding environment and concentrating them on the carbon surface.
Because of this ability to absorb and remove organic chemicals, activated carbon is used in a variety of applications, mostly related to the removal of pollutants and contaminants from the environment.
Activated carbon can be produced from a wide range of raw materials such as coconut shell, coal, peat and wood etc.
The raw material determines to a large extent, the properties of the final activated carbon and, in particular, the ability of the carbon to absorb different materials.
All activated carbon contain micropores, mesopores and macropores within their structure :
- micropores have a diameter of less than 2 nanometres
- mesopores have a diameter of 2 to 50 nanametres, and
- macropores have a diameter of over 50 nanometres.
The distribution of the pore size is determined by the raw material used and the activation process employed.
Coconut shell-based activated carbons have a predominance of micropores measuring under 1 nanometres in diameter and are highly efficient in absorbing small gaseous molecules in application where the contaminant concentration is low.
Coal based activated carbon contain mainly mesopores measuring around 20 nanometres in diameter, they are capable of absorbing a large range
Of molecules and are used in a wide variety of applications requiring the removal of molecules of varying size.
Wood / peat based activated carbon have a high proportion of mesopores and macropores and are suitable for absorbing large molecules from solution.