One of the first adequate explanatory theories of adsorption phenomena is the well-known Langmuir adsorption model. It is believed that the majority of theoretical treatments of adsorption phenomena are based on or at least could easily be traced back to the analysis developed by Irving Langmuir. His analysis is predicated on the following key assumptions:
Molecules are adsorbed at discrete active sites on the surface,
Each active site interacts and adsorbed with only one adsorbate molecule (mono-layer coverage),
The adsorption sites are all energetically equivalent (homogeneous), and there is no interaction between adjacent adsorbed molecules.
The interactive graph below consider the Langmuir Isotherm case for a binary gas-phase mixture of A and B. Vary the heats of adsorption of each species, the temperature, and the ratio of partial pressures to see what the effect of these paramters are on the fractional surface coverage of the two species.