What is the Difference Between Absorption and Adsorption?

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The main difference between absorption and adsorption lies in the way substances interact with each other. Here are the key differences between the two processes:

  • Absorption:
  • Involves the mass transfer of particles into another material, forming a solution.
  • Occurs when molecules pass into a bulky material, such as a liquid or solid.
  • The absorbed molecules cannot be easily separated from the absorbent.
  • Examples include a paper towel absorbing water or gases being absorbed into liquids.
  • Adsorption:
  • Involves the adhesion of particles onto the surface of a substance.
  • Occurs when atoms, ions, or molecules from a substance (gas, liquid, or dissolved solid) adhere to a surface of the adsorbent.
  • The adsorbed molecules can be easily removed.
  • Examples include adsorption chillers used with refrigerants, water purification, or adsorption cooling used in air conditioning.

In summary, absorption is a process where molecules are taken up by a material and dispersed throughout the material, forming a solution. Adsorption, on the other hand, is a process where molecules adhere to the surface of a material without forming a solution.

Comparative Table: Absorption vs Adsorption

Here is a table comparing the differences between absorption and adsorption:

Property Absorption Adsorption
Definition The process in which a fluid is dissolved by a liquid or a solid (absorbent) The process in which atoms, ions, or molecules from a substance adhere to a surface of the adsorbent
Phenomenon Bulk phenomenon Surface phenomenon
Heat exchange Endothermic process Exothermic process
Temperature Not affected by temperature Favored by low temperature
Rate of reaction Occurs at a uniform rate Steadily increases and reaches equilibrium
Concentration Same throughout the material Higher concentration on the surface of the adsorbent

In summary, absorption occurs when a substance is dissolved in a liquid or gas, while adsorption takes place when molecules of one substance stick to the surface of another substance. Adsorption is a surface-based process, whereas absorption is a bulk process.