Many pollutants both natural and synthetic are gaseous in nature and require specific technology to effectively remove the pollutant from an exhaust or process gas stream.

Adsorption is helpful in controlling pollution. It is a process of mass transfer in which a porous solid comes in contact with a liquid or gaseous stream to selectively remove pollutants or contaminates by depositing or absorbing them onto solid. The contaminates being removed are referred as adsorbate and solid doing the absorbing  called absorbent.