What is Adsorption?
Adsorption is the adhesion of molecules to the surface of a solid or liquid. The molecules get accumulated 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. It 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.
Mechanism of Adsorption
The process of adsorption arises because the forces acting on the surface particles of a substance are not the same as those 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 tend to attract adsorbate particles. This leads to the process of adsorption.
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||Bulk phenomenon.||A surface phenomenon.|
|Heat exchange||Endothermic process||Exothermic process|
|Temperature||No effect of temperature.||It works at a lower 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 the adsorbent is different from that in bulk.|