Naslov
Attenuated total reflection – Infrared spectroscopy applied to the study of mineral – aqueous electrolyte solution interfaces: A general overview and a case study

Autori
Lefèvre, Grégory ; Preočanin, Tajana ; Lützenkirchen, Johannes

Vrsta, podvrsta i kategorija rada
Poglavlja u knjigama, znanstveni

Knjiga
Infrared Spectroscopy - Materials Science, Engineering and Technology / Book 1

Urednik/ci
Theophanides, Theophile

Izdavač
IntechOpen

Grad
Rijeka

Godina
2012

Raspon stranica
98-122

ISBN
978-953-51-0537-4

Ključne riječi
Attenuated total reflection. solid/liquid interface, adsorption, surface complexation

Sažetak
The present chapter gives an overview of the application of Attenuated total reflection – Infrared spectroscopy (ATR-IR) to the environmentally important mineral – aqueous electrolyte interface. At these interfaces the important adsorption processes occur that limit the availability of potentially toxic solutes. These retention processes may retard for example the migration of solutes in aquifer system or even immobilized them on the aquifer material, which is usually a natural mineral. In this context (oxy)(hydr)oxide mineral are of major importance. At the surface of these minerals surface functional groups exist that are able to bind metal ions and organic ligands as well as they may promote the formation of so-called ternary surface complexes involving both metal ions and some ligand. To be able to quantify these retention phenomena in porous media (such as aquifers or soils) a physical model of solvent movement is coupled to an adsorption model (usually some variant of the surface complexation approach). The intent is to invoke as much understanding of the adsorption process as possible. This in turn requires the study of the adsorption process at the molecular level. Various spectroscopic approaches have been used to resolve the adsorption mechanism, one of the being ATR-IR. We give an introduction to the approach and an overview its possible applicability of this technique (and discuss in this context its use in contributing to the understanding of the acid-base chemistry of (oxy)(hydr)oxide mineral surfaces, the adsorption of anions and cations like the uranyl-ion, and the formation of ternary surface complexes). We highlight previous studies and point to some controversary issues in selected studies that continue to exist despite extensive research. We try to relate selected studies to other vibrational spectroscopies like sum frequency generation that are like ATR-IR surface sensitive, but probably even more so. Finally we discuss results from a study on the mineral gibbsite (Al(OH)3) in the presence of 5- sulfosalicilic acid. We show how ideally such a study should be designed, starting from the study of the gibbsite-electrolyte solution system (i.e. in absence of 5-sulfosalicilic acid) and that of 5-sulfosalicilic acid in aqueous solution (i.e. in the absence of gibbsite). Furthermore, we show that it is necessary to study in aqueous solution the interaction of 5-sulfosalicilic acid with dissolved aluminium, since the pH – dependent solubility of gibbsite will ultimately cause the appearance of aluminium ions in solution. Finally the system involving gibbsite and 5- sulfosalicilic acid is discussed. We relate the data to calculations of the species distribution for the solution systems, which indicate the dominant aqueous species thus facilitating the assignment of bands.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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