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the adsorption heat is found, up to a value corresponding to the bulk heat of

If a molecule contacts a solid adsorbent, it is exposed to various interaction fields, such as dispersion attraction, φD; repulsion, φR; induced polarization, φP;

Specific interactions as the acid-base interaction with the active site, φAB, if the

The dispersion or London forces among adsorbed nonpolar molecules and all types of adsorbents takes place when the transient dipoles turn out to be correlated; then, the dipoles of the nonpolar adsorbed species prompt a dipole in the atoms of the adsorbed species that act together to reduce the energy of the adsorption system. Hence, due to the correlation, the prompted dipoles created in the entire arrangement do not disappear, generating a dipole–dipole collaboration, dispersion interaction being intensity dependent on the polarizability of the adsorbate mole-

Additionally, the electrostatic contribution to the potential includes the dipole induced, dipole permanent and quadrupole terms, where, the induced polarization term occurs when nonpolar molecules within an electric field are polarized, and then an induced dipole moment is produced, the permanent dipole and quadrupole terms being caused by molecules whose structures produce permanent dipoles and quadrupoles; for example, H2O, H2S, SO2, and NH3 are molecules with a high dipole

The electrostatic attractive interactions are stronger than the dispersion interactions; however, dispersion is the fundamental attractive force present during adsorption in all adsorbate-adsorbent systems, for example, in the case of molecules like H2, Ar, CH4, N2, and O2. Given that the dipole moments of these molecules are zero, the quadrupole moment is very low or absent, and the polarization effect will only be noticeable in the case of adsorbents with high electric fields; the dispersion and repulsion interactions are responsible for the adsorption effect present in all adsorption gas-solid systems; therefore, they are nonspecific

moment, whereas CO2 is a molecule with a high quadrupole moment [1].

permanent dipole, φEμ; quadrupole, φEQ; and sorbate-sorbate, φAA.

condensation of the CO2 molecules [26–28].

10. Adsorption interaction fields

Applied Surface Science

surface contains hydroxyl bridge groups.

cule and the adsorbent surface atom [40].

interactions [2].

88

Rolando Roque-Malherbe<sup>1</sup> and Carlos de las Pozas del Rio2 \*


\*Address all correspondence to: carlos.delaspozas@uss.cl

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
