Adsorption . Separation of liquids, gases, colloids or suspended matter in a medium by adhesion to the surface or to the pores of a solid.
Summary
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- 1 Story
- 2 Adsorption processes
- 3 Types of adsorption
- 1 Electric adsorption
- 2 Physical adsorption
- 3 Chemical adsorption
- 4 Applications
- 5 References
- 6 Sources
History
The term adsorption appears to have been introduced by Kaiser [1] in 1881 to connote gas condensation on free surfaces, as opposed to gaseous absorption where gas molecules penetrate into the solid. Adsorption (strictly speaking, physical adsorption) has been defined by the IUPAC as the enrichment or emptying of one or more components in an interface. Actually, in 1909 , McBain [2]He proposed the term sorption to encompass three types of phenomena: adsorption on surfaces, absorption within the solid, and capillary condensation that occurs inside the pores. But, perhaps for reasons of euphony, the term was never widely used and the word adsorption is frequently used to denote interchangeably capillary condensation or surface adsorption.
Adsorption processes
Adsorption is a process by which matter is removed from one phase and concentrated on the surface of another phase (generally solid). The substance that is concentrated on the surface or adsorbed is called “adsorbate” and the adsorbent phase is called “adsorbent”. The reverse process of adsorption is known as desorption. It should not be confused with Absorption since the characteristic that distinguishes them is that in an adsorption process the fluid is not incorporated into the volume of the material, but is retained on its surface and in the absorption the molecules or atoms of a phase penetrate almost uniformly in those of another phase constituting a “solution” with this second.
Types of adsorption
Electric adsorption
When the attraction between the solute and the adsorbent is of an electrical type, ion exchange being the most representative example for what is often called exchange adsorption, which is a process by which the ions of a substance are concentrated in a surface as a result of electrostatic attraction at charged places on the surface.
Adsorption process diagram
Physical adsorption
Or also known by Van der Waals forces produced by the forces that produce it where the adsorbed molecule is not fixed in a specific place on the surface, but rather is free to move within the interface. It occurs mainly at low temperatures. The adsorption of most organic substances in water with activated carbon is considered to be physical in nature.
Chemical adsorption
It is when the adsorbate undergoes a chemical interaction with the adsorbent, the adsorption energies are high, of the order of those of a chemical bond , because the adsorbate forms strong bonds located in the active centers of the adsorbent. This adsorption is usually favored at a high temperature.
Most of the adsorption phenomena are combinations of the three forms of adsorption and in fact, it is not easy to distinguish between physical and chemical adsorption.
Applications
Fundamentally, adsorption is used for air drying , water purification, elimination of unwanted odors, color and flavor, either of gases, sugary solutions or oils used in perfume shops, waste treatment, obtaining nitrogen, among others.
