Langmuirisotermer

A Langmuir isotherm is a mathematical model used to describe the adsorption of molecules onto a solid surface from a liquid or gas phase at a constant temperature. Named after the American chemist Irving Langmuir, who developed the model in 1918, it provides insights into surface phenomena and the nature of adsorption processes.

The Langmuir isotherm assumes that adsorption occurs at specific homogeneous sites on the surface, with each site capable of holding only one molecule (monolayer coverage). It also presumes that all sites are energetically equivalent and that there is no interaction between adsorbed molecules. Under these conditions, the model relates the amount of adsorbed substance to its concentration (or partial pressure) in the surrounding fluid.

Mathematically, the Langmuir isotherm is expressed as:

q = (q_max * K * C) / (1 + K * C)

where q is the amount of adsorbed substance per unit weight of adsorbent, q_max is the maximum adsorption capacity corresponding to a complete monolayer, K is the equilibrium constant related to the affinity between the adsorbate and adsorbent, and C is the concentration (or pressure, in the case of gases).

The Langmuir model is widely used in fields such as catalysis, environmental science, and surface chemistry to analyze and predict adsorption behavior. Despite its simplifying assumptions, it effectively describes systems where monolayer adsorption dominates and provides a foundation for understanding more complex adsorption phenomena.