Difference between absorption and adsorption | Absorption vs Adsorption

The major key difference between adsorption and absorption is that one is a surface process and the other a bulk process. Absorption is one substance that enters the bulk or some volume of the another substance e.g. gas absorbed by a liquid. While the adsorption takes place on the surface of a substrate. Here this article gives information about the difference between absorption and adsorption are listed below.

Definition of absorption:

Adsorption is a surface, the accumulation of a gas or liquid or a solid. Absorption can be refined further based on the strength of the interaction between the adsorbent and the adsorbed molecules. 


Definition of adsorption:

Adsorption is a surface process, the accumulation of a gas or liquid or solid. Adsorption can be refined further based on the strength of the interaction between the adsorbent and the adsorbed molecules.

The main key difference between absorption and adsorption are listed below:


  • Absorption is a bulk phenomenon, adsorption is a surface phenomenon.
  • Absorption is mostly an endothermic process while adsorption is a mostly exothermic process.
  • Absorption is not affected by temperature, while the adsorption is favored by low temperatures.
  • Absorption is an assimilation of using a molecular species throughout the bulk of the solid or some liquid is termed as absorption, while the Accumulation of the molecular species at the surface rather than in the bulk of the solid or liquid is termed as adsorption.
  • Absorption occurs at a uniform rate, Adsorption is steady increases and reaches equilibrium.
  • Absorption is the same throughout the material while adsorption is the concentration on the surface of adsorbent is different from that in the bulk.
  • Absorption is material get absorbed into other material throughout the availability of space and also due to the properties of each material while the adsorption is the adsorbates bind onto the surface of the adsorbent most commonly through van der walls interaction or through covalent bonds.
  • During the process of absorption, the concentration of absorbed substances does not show any significant change. It remains to show significant change. IT remains constant throughout the medium while during the process of adsorption the concentration of the adsorbed substance changes from bulk to the bottom of the adsorbent.
  • Absorption can be categorized into two types; physical and chemical absorption while the adsorption can be categorized into two types; Chemisorption and physisorption.
  • The concept of absorption is applied for in cold storage, ice production, turbine inlet cooling, and refrigerant absorption, chiller for space cooling applications. It is also used in the hydrogenation of oils and carbonation of beverages. The concept of adsorption is applied in air conditioning, chiller, water purification, chillers, synthetic resin and in the development of non-stick coating and in various biomedical devices.
  • The rate of absorption maintains a steady-state throughout the process. The stated state marinated despite increases or decreases in the temperature while the rate of adsorption is usually high in the initial stages of the process, after a few minutes, it begins to decreases until equilibrium is reached. Increases in temperature increase the rate of adsorption decreases.
  • Absorption is comparatively slow than adsorption and the equilibrium take place slowly. While Adsorption is a rapid process. The equilibrium takes place quickly. 


Adsorption Examples:

  1. Nickel, platinum, and palladium is these adsorbent are widely used an as a catalyst in many organic processes such as hydrogenation of oils.
  2. Activated charcoal is used as an adsorbent with a wide range of applications. For example, it is used in the purification of gases and water or as an air filter in gas masks.

Absorption Examples:

  1. Absorption of water by a sponge.
  2. Absorption of oxygen from air by water.
  3. Absorption of ammonia by water.
  4. Removal of hydrogen sulfide biogas. In this process, hydrogen sulfide is first absorbed into water and after that treated with iron oxide.

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