2.1.2 Adsorption
It refers to the process by which molecules of a substance, such as a gas or a liquid, collect on the surface of a solid. It differs from absorption, in which a fluid permeates or is dissolved by a liquid or solid (Tondeur & Teng, 2008). It could be physical or chemical. In physical adsorption processes, gas molecules adhere to the surface of the solid adsorbent as
a result of the molecules attraction force (Van der Walls Forces). Chemical adsorption involves a chemical reaction. Usually, adsorbents are 12 μm to 120 μm high porosity solid grains, inert to the treated fluid. The most used adsorbents for CO2 are activated charcoal,silica gel, zeolites and synthetic resins.