Adsorption – Theoretical aspects

Adsorption separation technology is one of the most important separation technologies, particularly among those not based on vapor-liquid equilibrium. It is widely used for the separation and purification of gases and liquids in a wide variety of fields, from the petroleum, petrochemical and chemical industries to environmental and pharmaceutical applications. Typical industrial applications include :

• production of industrial gases (oxygen, nitrogen, hydrogen);

• separation of hydrocarbons (e.g. linear and branched kerosenes);

• air, water and effluent treatment to eliminate pollutants (pesticides, chlorinated solvents, sulfur compounds, odors, VOCs, heavy metals, etc.);

• drying, drug production, etc.

Adsorption separation is based on the selective adsorption (either thermodynamic or kinetic) of different gaseous or liquid constituents by adsorbents, thanks to specific interactions between the adsorbent surfaces and the adsorbed molecules. One of the essential features of adsorption technology is its transient and generally cyclic operation, since after an adsorption phase, the adsorbents must be partially or completely regenerated for their next use. Separation performance depends, non-trivially, not only on thermodynamic properties, but also on kinetic and hydrodynamic properties.

The various aspects of adsorption processes are the subject of two separate articles. In the first article, theoretical considerations of adsorption processes such as adsorbents, modeling of adsorption isotherms, transfer phenomena in adsorbent grains and dynamic behaviors of a (fixed) adsorbent bed are presented. More practical aspects of adsorption processes are covered in [J 2 731] .