Absorption vs. Adsorption

The main difference between absorption and adsorption is, absorption is the process in which fluid is dissolved by either solid or liquid. On the contrary, adsorption is the process in which ions, molecules or atoms from a substance like gas, solid or liquid, adhere to surface of adsorbent.

What is Absorption?

Absorption is a process in which one substance enters into other substance completely. It is process in which one atom or molecule is sucked inside of a volume of other molecules. It has to be a part of substance by completely entering into it. It could be a chemical or physical process. For instance, carbon dioxide could be absorbed into potassium carbonate’s solution. This is an example of chemical absorption, since a reaction takes place. Another example could be dissolving air inside water. This is physical absorption since air is entering inside water by equilibrium pressure. When any substance or material imbibes some amount of liquid or gas inside then that material is said to have absorbed the other material. Hence, in absorption, something moves inside a material.

What is Adsorption?

Adsorption is the process in which gas or liquid is not absorbed but it is only formed over the surface. For synthetic reasons and water purification, the phenomenon of adsorption is widely used in industries. It involves adhesion. A substance just hangs on to the other substance in this process without entering inside it. For instance, carbon dioxide sits on the surface of adsorbent inside of pressure swing adsorbent unit., it sits on the surface of solid adsorbent.

Key Differences between Absorption and Adsorption

  1. Assimilation of molecular species throughout bulk of solid or liquid is termed as absorption. Accumulation of molecular species at surface and not entering into it is termed as adsorption.
  2. Absorption is a bulk phenomenon while adsorption is a surface phenomenon.
  3. Absorption is an endothermic process while adsorption is an exothermic process.
  4. Absorption is not affected by temperature and adsorption is favored by low temperature.
  5. Absorption occurs at a uniform rate while adsorption’s rate increases steadily and then it ultimately reaches equilibrium.
  6. Concentration is absorption is same throughout the whole material. Concentration on the surface is different in adsorption from that in the bulk.
  7. Absorption is used commercially in chillers and water purification.
  8. Absorption is related to volume while adsorption is related to the surface.
  9. Absorption involves dissolution and diffusion while adsorption involves adherence.
  10. In absorption, energy of a photon is absorbed by another entity.

Video Explanation

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