What is Adsorption?

About Adsorption: 

• It refers to the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to the surface of a material.
• It is considered a surface phenomenon that creates a film of the adsorbate on the surface of the adsorbent (a solid material, for instance).
• Materials that are used to adsorb gases or dissolved substances are called adsorbents; the adsorbed molecules are usually referred to collectively as the adsorbate.
• How Adsorption Works?
  • Adsorption depends on surface energy.
  • The surface atoms of the adsorbent are partially exposed, so they can attract the adsorbate
  • Adsorption may result from electrostatic attraction, chemisorption, or physisorption.
• Characteristics of Adsorbents:
  • Typically, adsorbents have small pore diameters so that there is a high surface area to facilitate adsorption.
  • The pore size usually ranges between 0.25 and 5 mm. 
  • Industrial adsorbents have high thermal stability and resistance to abrasion.
  • Depending on the application, the surface may be hydrophobic or hydrophilic.
  • The adsorbents come in many shapes, including rods, pellets, and molded shapes. 
  • Examples of adsorbents include Silica gel, Alumina, Activated carbon or charcoal, Zeolites, Adsorption chillers used with refrigerants, Biomaterials that adsorb proteins, etc.
• Adsorption is a different process from absorption, in which a substance diffuses into a liquid or solid to form a solution.
• Adsorption phenomena are operative in most natural physical, biological, and chemical systems, and adsorption operations employing solids such as activated carbon and synthetic resins are widely used in industrial applications and for the purification of waters and wastewaters.