Adsorption isotherms for single

Fig.4 and Fig.5 show adsorption isotherms for single component systems, obtained from fixed bed experiments and molecular simulation, respectively. Adosorption equilibria were simulated well. Except EtOH system, quantitative order of amount adsorbed was good agreement with experimental data. As for BEN and TOL systems, the amount of adsorbed for simulations were lower than experimental data. So it is necessary to examined van der Waals parameter for benzene ring. Fig.6 and Fig.7 show adsorption equilibria For binary component systems, obtained from fixed>bed experiments and molecular simulation, respectively. These are examples, which show azeotropic adsorption. Especially, IPA-TCE, BEN-EtOH systems show two azeotropic points. Result of simulation shows only one azeotropic point. More investigative is necessary. 

J. Turkevich We have been presented a series of correlations on variation with temperature of adsorption isotherms for single adsorbate on a given adsorbant. Until the discovery and development of crystalline zeolite adsorbants, charcoal, silica gel, and alumina were not well characterized as to pore distribution and homogeneity of surfaces. Now we have well defined adsorbants. Are they so well defined that we can characterize their adsorbant power by an isotherm, for any adsorbate, by one or two numbers ... 

Adsorption Isotherm for Single and Mixed Surfactant Systems... 

FIG. 4 Adsorption isotherms for single solutes experimental data for (A) 1,1,1-trichloroethane and ( ) trichloroethylene, and (—) Langmuir isotherm. 

Scamehorn et. al. (19) reported the adsorption isotherms for a binary mixture of anionic surfactants. A formal adsorption model developed for single surfactant systems ( ) was extended to this binary system and shown to accurately describe the mixed adsorption isotherms (19). That theoretically based model was very complex and is probably not feasible to extend beyond two surfactant components. 

An adsorption isotherm for a single gaseous adsorptive on a solid is the function which relates at constant temperature the amount of substance adsorbed at equilibrium to the pressure (or concentration) of the adsorptive in the gas phase. The surface excess amount rather than the amount adsorbed is the quantity accessible to experimental measurement, but, at lower pressures, the difference between the two quantities becomes negligible (see Appendix II, Part I, 1.1.11). 

The t method for the determination of surface areas has been developed by de Boer and his pupils [12]. They showed that the nitrogen adsorption isotherm for a large number of nonporous solids can be represented by approximately one single curve when the ratio vj A is plotted as a function of the relative pressure. This so-called common t curve, a type II isotherm, is reproduced in Fig. 12.5. On the right-hand side Y axis the volume (STP) of adsorbed nitrogen per unit surface... 

Integration of the single-pore isotherms over the PSD produced the total adsorption isotherm for the model carbon, which can be compared with the experimental data. This comparison is shown in Figure 4. 

In this section a short overview is given of preparative chromatography and the determination of adsorption isotherm parameters - single and competitive - to be used for computer-assisted optimization of separations. 

Here n is the number of components in the system, coefficients a, and b, are the coefficients of the single-component Langmuir adsorption isotherm for component /. The coefficient bt is the ratio of the rate constants of adsorption and desorption, so it is a thermodynamic constant. The ratio ajb, is the column saturation capacity of component / [13],... 

As an example, adsorption isotherms for a competitive adsorption of two molecules will be considered. A bulky molecule (A) requires several sites m for adsorption. Substance B is a one centred molecule, which adsorbs onto a single site. 

Substituting Equation 5.133 into Equation 5.132 and rearranging leads to the Langmuir isotherm for single-component, associative adsorption... 

In heterogeneous reactions at a solid surface, molecules adsorbed on the surface often play a fundamental role in the reaction mechanism. For a homogeneous surface where only a monolayer of adsorbed material is formed, the surface adsorption is often described by the Langmuir adsorption isotherm. For adsorption of a single substance from solution, the isotherm expresses a relation between the amount of substance adsorbed and the concentration c of the adsorbing species in solution next to the surface... 

The fractional surface coverage by each component follows the Langmuir isotherm for single-site adsorption. Hence,... 

Shown in Fig. I is a typical adsorption isotherm for a single-component surfactant adsorbing from an aqueous solution surface for which the head group of the monomer has an attractive interaction, such as an anionic surfactant adsorbed on a positively charged surface. The x-axis is the equilibrium concentration of surfactant in solution, and the y-axis is the amount of adsorbed surfactant, in moles or molecules or mass per area or adsorbent weight. 

FIGURE 24 Adsorption isotherms for CO on Pt(111) single-crystal surfaces. 

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