10. Adsorption interaction fields

If a molecule contacts a solid adsorbent, it is exposed to various interaction fields, such as dispersion attraction, φD; repulsion, φR; induced polarization, φP; permanent dipole, φEμ; quadrupole, φEQ; and sorbate-sorbate, φAA.

Specific interactions as the acid-base interaction with the active site, φAB, if the surface contains hydroxyl bridge groups.

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 molecule and the adsorbent surface atom [40].

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

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 interactions [2].

Author details

89

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

Synthesis, Characterization, and Adsorption Properties of Nanoporous Materials

DOI: http://dx.doi.org/10.5772/intechopen.83355

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

2 University San Sebastian, Santiago, Chile

provided the original work is properly cited.

1 BioTECNOS Limited, Talca, Chile-San Sebastian University, Santiago, Chile

© 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,

\*

Synthesis, Characterization, and Adsorption Properties of Nanoporous Materials DOI: http://dx.doi.org/10.5772/intechopen.83355
