Sorption of sulfate ions onto hematite studied by attenuated total reflection-infrared spectroscopy: Kinetics and competition with other ions

In this paper, after a short discussion about the use of attenuated total reflection-infrared spectroscopy (ATR-IR) to study sorption of inorganic ions onto iron oxides, results of ATR-IR spectroscopy of surface complexes adsorbed on hematite are presented. Kinetics of sorption of sulfate ions was followed, showing an equilibrium after half an hour. The infrared band was assigned to a monodentate surface complex with a low contribution of a bidentate complex with help of second-derivative spectral analysis. The effect of several ions (SeO42-, ReO4-, UO22+) after sorption of sulfate (10 μM) was investigated. Selenate ions (10–100 μM) were shown to compete with sulfate ions, while perrhenate ions (1–100 μM) did not desorbed sulfate complexes. Experiments were also carried out in the hematite–sulfate (10 μM)–uranyl (10 μM) system, but no ternary complex was observed.