Bilangmuir isotherm

This model is directly derived from the Langmuir isotherm. It assumes that the adsorbent surface consists of two different types of independent adsorption sites. Under this assumption, the adsorption energy distribution can be modeled by a bimodal discrete probability density function, where two spikes (delta-Dirac functions) are located at the average adsorption energy of the two kinds of sites, respectively. The equation of the Bilangmuir isotherm is... 

Although the Bilangmuir isotherm is an ideal model (in the sense that real surfaces with exactly the characteristics described by the Bilangmuir model do not exist), it is often successful in describing the adsorption of enantiomers on chiral stationary phase. The reason is that, because of their... 

FIGURE 10.12 Adsorption data of buspirone (o), doxepin (V), and diltiazem ( ) and best Bilangmuir isotherms (continuous and dotted lines). Mobile phase is acetonitrile buffer=35 65 buffer is 0.1 M phosphate, pH 3.0, T = 25°C. (Reproduced from Quinones, I. et al., J. Chromatogr. A, 877, 1, 2000. With permission from Elsevier.)... 

The mathematical representation of the bilangmuir isotherm in Eq. (7.5) represents interactions on two different types of sites, each of which is described by Langmuir-type interactions. 

FIGURE 10.11 Adsorption isotherms of A-benzoyl-L-alanine (1) and iV-benzoyl-D-alanine (2). Experimental data fitted to the Bilangmuir model. (Reproduced from Jacobson, S. et al., J. Am. Chem. Soc., 112, 6492, 1990. With permission from American Chemical Society.)... 

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