Question

What is the mechanism of adsorption?

Answer 1

it is an exothermic process. When the solid surface is exposed to a gas or a liquid, its molecules accumulate on the solid’s surface. This is adsorption. It is a surface phenomenon. There is the release of energy taking place during the process so it is exothermic.

Complete answer:
Adsorption is the phenomenon of the deposition of molecular species onto the surface. The molecular species that gets adsorbed on the surface is known as adsorbate and the surface on which adsorption occurs is known as adsorbent. Common examples of adsorbents are the clay, silica gel, colloids, metals etc. this is a surface phenomenon. The opposite phenomenon is called desorption, which is the removal of adsorbent from the surface of the adsorbate.
Adsorption is of two types – physical adsorption and chemical adsorption.
Physical adsorption-
It is also known as physisorption. It is a weak phenomenon. The adsorption is caused by physical forces. There is no specificity in this case. It is reversible. It is an exothermic process and no activation energy is required.
Chemical adsorption-
It is also known as chemisorption. It is a strong phenomenon. The adsorption is caused by chemical forces. It is a highly specific and irreversible process. It requires activation energy.
Mechanism of adsorption-
Inside the adsorbent, the particles are surrounded by some kind of atoms or molecules and so all the forces acting between them are mutually balanced. But the particles present on the surface are not surrounded by particles of the same kind and hence they possess an unbalanced or residual attractive force. The unbalanced residual forces on the surface tend to attract the adsorbate particles. They attract the adsorbate molecules towards them and get balanced. This leads to the process of adsorption. During this process, there is a release of energy. The extent of adsorption increases when the surface area increases at a given temperature and pressure.

Note:
adsorption may not be confused with absorption. Both are two different phenomenons. In adsorption, the adsorbate adheres to the surface of the adsorbent by certain forces. In absorption, the molecules are dissolved or diffused into the adsorbent and form a solution. Adsorption has a wide number of applications. Example- control of humidity, removal of coloring matter from solutions, separation of inert gases, etc.