Langmuir isothenn

Langmuir isothenn for adsorption as atomic carbon monoxide... 

If Langmuir adsorption occurs, then a plot of 9 versus p for a particular isothenn will display the fonn of equation (Al.7.3). Measurements of isothenns are routinely employed in this manner in order to detennine adsorption kinetics. 

FIGURE 1.8. The Frumkin isothenn (full line) is a high quality fit to the low concentration region with a transition (see Figure 1.5) to a Langmuir isotherm (dotted line) for the higher concentration region. 

An example of a phenol adsorption isothenn onto an activated carbon cloth is given in Fig. 3. Experimental data are modeled with the Langmuir and Freundlich equations. A graphical construction is presented the slope of the adsorption path is equal to - Vim according to the mass balance equation between fluid and solid phases. From a given Co, this graphical construction enables the final concentration Cf to be determined. 

In the Heniy range of an adsoiption isothenn with / , or 0 or e oo the Henry coefficient He = n/p should be constant (with sufficient accuracy for chemical engineering). In Table 2.4-1 this requirement is fiilfilled by the equations of Langmuir, Branauer-Emmet-Teller, Toth, and Akgun-Mersmann. In the saturation range the final loading is with as the micropore... 

Figure 2. Olusttadon of typical measured isothenn curves of H2 and Dz (top) intercomparison of different soiptives by evaluation of e toimental data (data for He fonn [4]) at their normal boiling tempoatures in a Langmuir plot, which should yield a straight line when ai licable (bottom). 

Two porous materials relevant to cryosorption vacuum pumping were characterised by means of adsorption isothenns. Based on the example of the Langmuir isotherm, it is shown that the use of standard models may produce ambiguous results when tq)plied to non standard cases. 

Large-scale chromatography often is operated outside the littear range. If the species interact and the equilibrium amount of species i depends on the concentrations of all species present, the approach presented here is too simple and more complex mathematics are required. If the speices do not interact, (14.1-3) is still valid but a nonlinear isothenn must be used to relate to Cj. The solute velocity now depends on the solute concentration. For adsorption systems the isotherms often have a Langmuir shape. Then the equilibrium expression is of the form... 

This is an isothenn differing from Langmuir s in the exponent n affecting the activity. For 0, Equation 4.72 simplifies to... 

---