Models of Adsorption Isotherms in Liquid-Solid Equilibria

2 Models of Adsorption Isotherms in Liquid-Solid Equilibria 

1 Isotherm Models for Ideal Adsorption on Homogeneous Surfaces 

There are only two important models in the first category, the Langmuir and the Jovanovic isotherms. There are no adsorbate-adsorbate interactions and the adsorbate are localized. 

The kinetic derivation of the Langmuir isotherm presented in the case of gas-solid equilibria (Section 3.1.3) can be readily extended to the Uquid-solid equilibria. This isotherm can also be derived using a thermodynamic approach, in the case of a dilute solution [34]. 

Let us consider a two-component system, with a solvent (S) and a solute (A). The hquid-solid equilibrium can be written  

---

More complicated models take into account lateral interaction between the adsorbed molecules. One of these models was designed by Fowler and Guggenheim. It assumes ideal adsorption on a set of the localized sites, with weak interactions among molecules adsorbed on neighboring sites. It also assumes that the energy of interactions between two adsorbed molecules is so small that the principle of random distribution of the adsorbed molecules on the sorbent surface is not significantly affected. For liquid-solid equilibria, the Fowler and Guggenheim isotherm is empirically extended and written in the form ... 

---