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The Difference Between Absorption & Adsorption

Jackson Wallace

December 15, 2022

Although these two terms sound almost identical and are commonly used as synonyms by members of the general public - there is however a major difference in their meaning. 

What is Absorption?

Absorption refers to the act of atoms passing through or entering a bulky material, the molecules are either dissolved or diffused in the absorbent. Picture the act of using a sponge or piece of paper towel to soak up spilt liquid. Absorption is also commonly used in a variety of industrial products such as Oxygen Absorbers (Oxygen Scavengers) those of which are used to help in the preservation of food & pharmaceutical products. 

Sponge on white background

What is Adsorption?

Adsorption on the other hand refers to the scientific phenomenon of individual molecules, atoms or ions gathering on the surface of a material. In this process the substance that is absorbed is known as the adsorbate and the material on which it adheres too is referred to as the adsorbent.

The phenomenon of adsorption can often be broken down into two difference types - Chemisorption & Physisorption

What is Chemisorption?

Chemisorption occurs when gas molecules are bound to the surface by a bond that is formed via a chemical reaction.

What is Physisorption?

Physisorption occurs when gas molecules are bound by the sum of attractive between molecules and electrostatic forces. Physisorption is the process performed by most desiccant products including silica gel.