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 mu M) was investigated. Selenate ions (10-100 mu M) were shown to compete with sulfate ions, while perrhenate ions (1-100 mu M) did not desorbed sulfate complexes. Experiments were also carried out in the hematite-sulfate (10 mu M)-uranyl (10 mu M) system, but no ternary complex was observed. (c) 2006 Elsevier Ltd. All rights reserved.