Single-compound adsorption isotherms

To study the influence of the pore network connectivity on multicomponent adsorption equilibria, we used ethyl propionate, ethyl butyrate, and ethyl isovalerate as the adsorbates and Filtrasorb-400 and Norit ROW 0.8 activated carbon as the adsorbents. For predicting binary isotherms we used known parameters for single component adsorption of these compounds as previously determined. The effect of the pore network connectivity was taken into account in... 

All cases of practical importance in liquid chromatography deal with the separation of multicomponent feed mixtures. As shown in Chapter 2, the combination of the mass balance equations for the components of the feed, their isotherm equations, and a chromatography model that accounts for the kinetics of mass transfer between the two phases of the system permits the calculation of the individual band profiles of these compounds. To address this problem, we need first to understand, measure, and model the equilibrium isotherms of multicomponent mixtures. These equilibria are more complex than single-component ones, due to the competition between the different components for interaction with the stationary phase, a phenomenon that is imderstood but not yet predictable. We observe that the adsorption isotherms of the different compounds that are simultaneously present in a solution are almost always neither linear nor independent. In a finite-concentration solution, the amount of a component adsorbed at equilib-... 

This isotherm model has been used successfully to accoimt for the adsorption behavior of numerous compounds, particularly (but not only) pairs of enantiomers on different chiral stationary phases. For example, Zhou et ah [28] foimd that the competitive isotherms of two homologous peptides, kallidin and bradyki-nine are well described by the bi-Langmuir model (see Figure 4.3). However, most examples of applications of the bi-Langmuir isotherm are found with enantiomers. lire N-benzoyl derivatives of several amino acids were separated on bovine serum albumin immobilized on silica [26]. Figure 4.25c compares the competitive isotherms measured by frontal analysis with the racemic (1 1) mixture of N-benzoyl-D and L-alanine, and with the single-component isotherms of these compounds determined by ECP [29]. Charton et al. foimd that the competitive adsorption isotherms of the enantiomers of ketoprofen on cellulose tris-(4-methyl benzoate) are well accounted for by a bi-Langmuir isotherm [30]. Fornstedt et al. obtained the same results for several jS-blockers (amino-alcohols) on immobilized Cel-7A, a protein [31,32]. 

Moreover, this porous compound is also applicable for efficient separation of mixed gases, CO2/N2 and C02/CF14, which are useful in air purification and methane transportation systems [235]. Kinetic diameters of CO2, N2, and CH4 are 3.30, 3.64, and 3.80A, respectively. The small pores of 4.0 x 4.0A within this compound has limited the packing of these three gas molecules within the micropores to a single-layer packing that simplifies the complicated adsorption phenomena and process. The adsorption isotherms for each component at different temperatures... 

The abilily of activated carbon to remove a broad spectrum of orj nic compounds from wastewater is well documented. The Freundlich single-solute isotherm constants, as tabulated in [32], are reproduced in Table 2. These data illustrate clearly the wide range of organic compounds of different structures, sizes, functionality, etc. that can be adsorbed by an activated carbon. It can also be observed that these compounds exhibit different adsorption characteristics. Indeed, the adsorption behavior is affected by various factors related to molecular structure [33], like the adsorbate solubility, the kind of substituent groups of aromatic compounds, the size of tire molecule, its polarity and its hydrophobicity. 

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