Difference between Adsorption and Absorption

Adsorption & Absorption

In Adsorption the substance whose molecules get adsorbed at the surface is called the adsorbate. The substance on whose surface the process takes place is called the adsorbent. It is a surface phenomenon.

Absorption is a separate mechanism from adsorption because molecules undergoing absorption are soaked up by the length, not by the air. Adsorption is based on the surface where a film of adsorbate is developed on the surface, and absorption includes the complete volume of the absorbing agent.

Table of Contents

Definitions of Adsorption and Absorption

What is Adsorption? 

Adsorption is the adhesion of molecules (or ions and atoms) to the surface of a solid or liquid. The molecules accumulate only at the surface and do not enter the bulk of the adsorbing material.

  • The substance whose molecules get adsorbed at the surface is called the adsorbate.
  • The substance on whose surface the process takes place is called the adsorbent.
  • It is a surface phenomenon.

What is Absorption?

Absorption is a physical or chemical effect or a mechanism in which electrons, molecules or ions join some bulk phase – solid or liquid substance. 

The Difference Between Adsorption and Absorption




Definition Assimilation of the molecular system throughout the bulk of the solid or liquid medium. Accumulation of molecular species at the bottom instead of the liquid or solid.
Phenomenon A bulk phenomenon. A surface phenomenon.
Heat exchange Endothermic process Exothermic process
Temperature The temperature has no effect. Influenced by low temperature
Rate of reaction Occurs at a uniform rate. Increases steadily and reaches equilibrium.
Concentration It is constant throughout the medium. The Concentration at the bottom of adsorbent is different from that in bulk.

Examples of Adsorbents

  • Some examples of good adsorbents include:
    Alumina gel
  • Silica gel
  • Zeolites
  • Activated carbon
  • Graphite

What is Desorption?

Desorption is the reverse process in which the adsorbed substance is removed from the surface of the adsorbent.

Mechanism of Adsorption

The process of adsorption arises due to the fact that the forces acting on the surface particles of a substance are not the same as that acting on the bulk of the material. Unlike the particles inside the bulk, on the exposed surface, the particles are not surrounded by atoms on all sides.

Consequently, the forces on the inside balance each other, whereas those on the surface are unbalanced. The unbalanced residual forces on the surface have the tendency to attract the adsorbate particles. This leads to the process of adsorption.

It is to be noted here that at a given temperature and pressure, the greater the surface area of adsorbent, higher is the extent of adsorption.

Frequently Asked Questions – FAQs


What is the difference between adsorption and absorption?

Adsorption compounds cling to the surface of the molecule, whereas absorption substances enter the bulk phase of a liquid or solid.


What is an example of adsorption?

The deposition of molecular species onto a surface is known as adsorption. Adsorbate refers to the molecular species that gets adsorbed on the surface, whereas adsorbent refers to the surface on which adsorption happens. Clay, silica gel, colloids, metals, and other adsorbents are common examples.


What are different types of absorption?

Physical absorption and chemical absorption are the two types of absorption processes, depending on whether there is a chemical reaction between the solute and the solvent.


What is the absorption process?

Absorption is a chemical process in which a material in one state is transferred to another substance in a different state.


What are the major types of absorption spectroscopy?

Infrared, atomic, visible, ultraviolet (UV), and x-ray waves are the most common types of waves recorded by absorption spectroscopy. The techniques used by each spectrophotometer are the same.

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