The phenomenon of attracting and retaining the molecules of a substance on the surface of a liquid or a solid resulting into a higher concentration of the molecules on the surface is called adsorption. The substance thus adsorbed on the surface is called the adsorbate and the substance on which it is absorbed is known as adsorbent. The reverse process i.e. removal of the adsorbed substance from the surface is called desorption. The adsorption of gases on the surface of metals is called occlusion.
Difference between Adsorption and Absorption:
|It is surface phenomenon i.e. it occurs only at the surface of the adsorbent.||It is bulk phenomenon i.e. it occurs throughout the body of the material.|
|In this phenomenon, the concentration on the surface of adsorbent is different from that in the bulk.||In this phenomenon, the concentration is same throughout the material.|
|Its rate is high in the beginning and then decreases till equilibrium is attained.||Its rate remains same throughout the process.|