Stern-Langmuir isotherm

Sterilization, in fermentation, 11 35-36 Sterilization-in-place (SIP), 11 40 Stern-Langmuir equation, 24 139 Stern-Langmuir isotherm, 24 138 Stern plane, 7 285-286 Steroidal ketones, dehydrogenation of,... 

The adsorption of ionic surfactants on hydrophobic surfaces may be represented by the Stern-Langmuir isotherm [17]. Consider a substrate containing sites... 

As this subject was covered in detail in Chapter 5, only a summary will be provided at this point. Surfactant adsorption is usually reversible, and hence thermodynamics can be applied for deriving the adsorption isotherm. Eor example, the adsorption of ionic surfactants onto hydrophobic surfaces may be represented by the Stern-Langmuir isotherm [13]. Consider a substrate containing sites (molm ) on which F molm of surfactant ions are adsorbed. The surface coverage 0 is (F/NJ and the fraction of uncovered surface is (1 — 0). The Stern-Langmuir... 

In order to calculate this distribution equilibrium of the liquid charge between the two layers (which may be called the Stern-layer and the Gouy-layer, respectively). Stern proceeds in a way somewhat analogous to the derivation of the adsorption isotherm of Langmuir. We will simplify Stern s equations by considering only the counter-ions, i.e. 

Stern assumed that a Langmuir-type adsorption isotherm could be used to describe the equilibrium between ions adsorbed in the Stern layer and those in the diffuse part of the double layer. Considering only the adsorption of counter-ions, the surface charge density cr, of the Stern layer is given by the expression... 

The basis for the discussion of adsorption on charged surfaces is the surface complexation model. The precept for this model is the use of the standard mass-action and mass-balance equations from solution chemistry to describe the formation of surface complexes. Use of these equations results in a Langmuir isotherm for the saturation of the surface with adsorbed species. There are of course other models that satisfy these precepts, but which are not generally referred to as surface complexation models, for example, the Stern model (J). 

Fig. 37a shows the results of measurements of Stern potentials ij/i in dependence on CTAB concentration Co- Calculated using Eq. (42), the corresponding dependence for surface charges, cr = cr(Co), is shown in Fig. 37b [46]. Measurements were performed at pH 6.5 in the background electrolyte, 5 x 10 M KCl. Experimental data are shown in Fig. 37 by points, whereas solid lines are plotted using Langmuir isotherm, which was recommended to describe adsorption data for weakly charged surfaces [52] ...

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