Langmuir Isotherms for a Binary Mixture

Langmuir isotherms are generated for each component in a binary gas-phase mixture of A and B. Vary the heats of adsorption of each component, the temperature, and the ratio of partial pressures with sliders. The molecules compete for adsorption sites but do not interact with each other, and this is taken into account in the form of the Langmuir isotherm. Vary the relative number of sites per molecule with a slider to account for larger molecules occupying more surface area than smaller molecules. The Langmuir isotherm for molecules A and B has the form:


Download the CDF file to view the simulation offline using the free Wolfram CDF player.

The number of molecules per site for components A and B are:
where Ki is the adsorption equilibrium constant for component i = A, B (1/bar), Pi is the partial pressure for component i = A, B (bar) and α is the saturation coverage of B to A.
where k is a pre-exponential factor (1/bar), λi is the heat of adsorption (kJ/mol), R is the ideal gas constant (kJ/[mol K]), and T is temperature (K).

where P is the total pressure P = PA + PB (bar), and r is the ratio of partial pressures.