Attenuated total reflection - infrared spectroscopy applied to the study of mineral-aqueous electrolyte solution interfaces: general overview and a case study

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 systems or even immobilize them on the aquifer material, which is usually a natural mineral. We give an introduction to the approach and an overview of its possible applicability (and 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 can be mentioned in general). Our contribution focuses on a review on the interaction of small organic molecules with oxidic surfaces and we highlight previous studies and point to some controversary issues in selected studies that continue to exist despite extensive research. Obviously such studies relate to other vibrational spectroscopies like Raman or sum frequency generation vibrational spectroscopies. Finally we discuss results from an experimental study on the mineral gibbsite (Al(OH)3) in the presence of 5-sulfosalicylic acid (5-SSA).