- Assumes a monolayer of adsorbate on the adsorbent surface. - Adsorption occurs on specific, uniform sites. - No interaction between adsorbed molecules. - Describes saturation behavior at high adsorbate concentrations.
Freundlich Isotherm:
- Empirically derived equation that describes a heterogeneous surface. - Adsorption occurs on multiple sites with varying affinities. - Adsorbate molecules interact and form multilayers.
BET Isotherm (Brunauer-Emmett-Teller):
- Assumes a multilayer formation on a heterogeneous surface. - Adsorption occurs in layers, with each layer having a constant adsorption energy. - Describes both monolayer and multilayer adsorption.
Type I Isotherm:
- Applies to microporous solids. - Shows a sharp rise in adsorption at low adsorbate concentrations, followed by saturation. - Indicates monolayer formation within the micropores.
Type II Isotherm:
- Describes non-porous or mesoporous solids. - Exhibits a gradual increase in adsorption and a plateau at high adsorbate concentrations. - Suggests the formation of multilayers on the surface.
Type III Isotherm:
- Indicates weak interactions between the adsorbate and adsorbent. - Adsorption increases steadily without reaching a plateau.
Type IV Isotherm:
- Exhibits a hysteresis loop during adsorption and desorption. - Indicates capillary condensation in mesoporous solids.
Type V Isotherm:
- Similar to Type I, but with a weaker initial rise in adsorption. - Suggests adsorption on a heterogeneous surface with both strong and weak sites.