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Absorption and Adsorption: What is the difference?


Absorption and Adsorption: What is the difference?

Although the terms "absorption" and "adsorption" seem same, they have different meanings and uses.


The word "absorption" is used in many different contexts, and each one of them has a distinct meaning.


Absorption in physics refers to the incorporation of a gaseous component, known as the "absorbate," into the volume filled by a liquid substance, known as the "absorbent."


Adsorption is the phenomena that happens when a substance, known as a "adsorbate," in a liquid or gaseous state, attaches to the wall of a solid, known as a "adsorbent."



What is absorption?

A physical phenomena known as absorption occurs when one or more parts of a gaseous mixture dissolve in a liquid through the process of mass diffusion. It is reversible because there are no chemical alterations involved.


Absorption is mostly employed in industry to purify gases, whether the gas is a product or a byproduct of a process. Reducing SO2 and CO2 in a gas stream in absorption columns is a typical use.



What is adsorption?

When a substance in a liquid or gaseous phase interacts with an adsorbing solid and is physically forced to attach to its surface, this is known as adsorption (London scattering force). This process is reversible because there is no exchange of electrons involved.


Less frequently, chemisorption takes place, which entails irreversible changes to the chemical composition of the adsorbent and adsorbate.


Adsorption is frequently used to clean gases and liquids. In the industrial setting, packed columns are frequently used to create a flow for the treated liquid or gas. Examples include extracting moisture from a gaseous stream by passing it through a column of activated alumina, which adsorbs the water molecule, and purifying water with activated carbon, which can bind to organic compounds like pesticides and hydrocarbons.


Activated carbon is the most often utilized adsorbent in industrial, commercial, and home activities.




The comparison of each of these processes is shown in the table below.



Comparative table of adsorption and absorption













The process through which particles of one substance—such as atoms, ions, or molecules—are dissolved in another.



Phenomenon when particles from gases, liquids, or dissolved solids are held on the surface of a solid or liquid object.






It’s a mass and volume phenomenon.



It’s a superficial phenomenon.



Sorbent state of aggregation






Solid and liquid.



Aggregate state of the solute



Liquid, gaseous.



Solid, liquid and gaseous.




Although the phrases absorption and adsorption sound alike, their applications and meanings are distinct, making it impossible to interchange or use either term at will.