Langmuir Adsorption Isotherm: This describes quantitatively the formation of a monolayer
adsorbate on the outer surface of the adsorbent, and after that no further adsorption takes place. Thereby, the
Langmuir represents the equilibrium distribution of metal ions between the solid and liquid phases [29]. The
Langmuir isotherm is valid for monolayer adsorption onto a surface containing a finite number of identical sites.
The model assumes uniform energies of adsorption onto the surface and no transmigration of adsorbate in the
plane of the surface. Based upon these assumptions, Langmuir represented the following equation: