Benzene adsoiption

Tlie values in Table 1.24 should be seen only as a first guide or rough approximation since the parameters could be widely different with different carbons. For instance, in Table 1.25, the Freundlich parameters aie presented for benzene adsoiption on several types of activated carbons. 

Dubinin reached the conclusion that the function was Gaussian after having studied the adsoiption of simple organic compounds like benzene, and finally the classical expression of Dubinin and Radushkevich (the D-R equation) was derived (Dubinin, 1966 Cheng et al., 2004) ... 

Figure 9.10. Differential energies of adsoiption of benzene (top) and n-hexane (bottom) at 20°C on three different graphitized thermal blacks (after Isirikyan and Kiselev, 1961).

All adsoiption/breaktlirough experiments were performed in vertical custom made quartz adsorbers equipped with a supporting glass fiit. Initially, the adsorbents were loaded inside the adsorber (between 1 or 2 grams), and heated in situ (250 - 450°C) while flowing either helium or nitrogen upwards. After activation treatment, the zeolite adsorbent under study was allowed to cool down to room temperature under. Next, a sulfur-free octane or benzene solution was allowed to flow downwards through the... 

Molecules whose kinetic diameter is about SA or smaller are able to pass through the windows of the X and Y zeolites and be adsorbed within the internal surface. Water (18) and benzene (19-21), for example, can be added as "spectator" guest molecules which do not participate in a reaction sequence in a direct chemical manner, but may strongly influence the course of reaction of another adsorbed reactant by controlling factors such as the site of substrate adsoiption or by influencing the diffusional or rotational motion of the reactants. The number and position of these guest molecules within a supercage may also be varied. 

Largely, the same principles apply for water treatment. Consequently, activated carbon is suitable for organic molecules that are nonpolai and of high moleculai- weight. Trichloroethylene, benzene, ethylbenzene, toluene, and xylene are easily adsorbed in the gas phase when activated carbon, for instance, is used. On the other hand, adsoiption is not preferably selected in applications in relation to aldehydes, ketones, and alcohols. In a successful application, reduction in emissions from 400-2000 ppm to under 50 ppm can be achieved (EPA, 1999), especially for VOCs witli boiling points between 20 -and 175 °C. 

Figure 11.14 Calcinated adsoiption of benzene and ethanol by activated carbon. Bartell and Shan, J. Ant Chen Sac. 51,...

If two adsorbates fill the same adsorption volume their adsorption mtentials will differ only because of differences in their molecular >ioperties. The ratio of adsoiption potentials was assumed by Dubinen SS] to be a constant which he deflned as an affinity constant (P) since t is a measure of the relative affinities of different molecules for a surface. Uring benzene as a reference vapor the affinity ratios for other vapors were determined [56]. 

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