Difference between adsorption and absorption

Absorption is the process in which a fluid is dissolved by a liquid or a solid whereas adsorption is the process in which atoms, ions or molecules from a substance adhere to a surface of the absorbent. Let us have a deep insight into the difference between adsorption and absorption. 

Adsorption :

• It is a phenomenon of concentration or assimilation of gas or a liquid at the surface of a solid or liquid.
• It is a surface phenomenon.
• It is a fast process.
• Equilibrium is attained easily.
• It depends upon the surface area of the adsorbent. 
• It is an exothermic process.
• It is favoured by low temperature.
• It is steadily increasing and reaches equilibrium.
• It is used in Air conditioning, water purification, synthetic resin. 

Examples : 

• Water vapours adsorbed by silica gel.
• NH₃ is adsorbed by charcoal.

Absorption :

• It is a phenomenon in which the substance assimilated is uniformly distributed throughout the body of the solid or liquid.
• It is a bulk phenomenon.
• It is a slow process.
• Attainment of equilibrium takes some time.
• No such effect is there.
• It is an endothermic process.
• It is not affected by temperature.
• It occurs at a uniform rate.
• It is used in cold storage, ice production, turbine inlet cooling, refrigerant. 

Examples :

• Water vapours absorbed by anhydrous CaCl_2.
• NH₃ is absorbed in water forming NH₄OH.

You can also read about the difference between physical adsorption and chemical adsorption.