Physical Concept of Adsorption

To illustrate the concept of adsorption consider a closed system consisting of a small number of gas phase molecules in contact with a solid surface.

1. Effect of Temperature

T1:	T2:

Note that:

• Adsorption is a dynamic equilibrium

• At higher temperature (T₂):
  • Greater ratio of gas phase molecules
  • Average time spent by a molecule on the surface (residence time) is lower (see red molecule).

2. Effect of Pressure

P₁ < P₂

P1:

P2: