Langmuirs theory and its application to

Macro-Kinetic Aspects of Langmuir s Theory and Its Application to Adsorption Dynamics 

As we have seen in Sections 2.5. and 2.6. there are different isotherms for the description of the adsorption density F or the interfacial tension y as functions of the known surfactant 

The basic model for the calculation of the adsorption flux of amphiphiles to an interface is shown in Fig. 2.13. This model consists of a so-called sublayer , the coordinate x is oriented normal to the interface. The second assumption is an equilibrium between the sublayer and the interface at any time. The weakest point in this physical model is the problem of the validity of an equilibrium adsorption isotherm in a non-equilibrium state. In any case close to the equilibrium state the adsorption isotherms provides a good approximation. 

The location of the sublayer at x=0 is an arbitrary but necessary part of the boundary conditions for the diffusion model. 

36) in its general form and Eqs (4.31) to (4.34) as particular cases have to be modified essentially in order to use them for the description of adsorption kinetics processes. This modification is the replacement of the bulk concentration c by the sublayer concentration c(0,t), which was first suggested by Baret (1969), which leads to Eq. (4.35) used in Chapter 4 as the basis for the so-called kinetic-controlled adsorption model. 

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