Definition
Adsorption at liquid interfaces involves the accumulation of molecules (adsorbates) at the boundary between two phases, reducing surface or interfacial tension.
Mechanism
Surface Activity: Molecules with both hydrophilic and hydrophobic regions orient themselves at interfaces.
Gibbs Adsorption Isotherm: Describes the relationship between surface tension and concentration.
where:
Γ is the surface excess concentration.
R is the gas constant.
T is the temperature.
γ is the surface tension.
C is the concentration of the adsorbate.
Factors Influencing Adsorption
Concentration: Higher concentrations increase adsorption until saturation.
Molecular Structure: Amphiphilic molecules adsorb more readily.
Temperature: Generally, adsorption decreases with increasing temperature.
Applications of Adsorption at Liquid Interfaces
Emulsion Stabilization: Surfactants adsorb at oil-water interfaces.
Foam Formation: Proteins and surfactants stabilize gas-liquid interfaces.
Drug Delivery: Adsorption affects drug release from carriers.