where Qm is a constant related to the area occupied by a monolayer of adsorbate and reflects the adsorption capacity (mg/g) of the adsorbent and b is a direct measure of adsorption intensity (L/g). A linearised form of Eq. (2) is:
Theoretically, the sorbent has a finite capacity for the sorbate, therefore, the saturation value is reached when no further sorption can take place. The Langmuir model is represented by the following equation: