Heavy metal adsorption on iron oxide and iron oxide-coated silica ...

3and Sigg, 1992; Gunneriusson et al. 1994; Nowack et al. 1996); the assumed surfacecomplexes are checked by the goodness of fit (Goldberg, 1991). Although theseapproaches are usually successful, the surface species used may not be physicallymeaningful. Fortunately, recent advances in identification of sorbed species by in-situspectroscopic techniques like X-ray absorption spectroscopy (XAS) and Fouriertransform infrared spectroscopy (FTIR) have made it possible to overcome this drawbackfor many systems of interest (e.g., Chisholm-Brause et al. 1990; Charlet and Manceau,1992; O'Day et al. 1994; Bargar et al. 1997a,b; Scheidegger et al. 1998; Manning et al.1998; Sahai et al. 2000; Trainor et al. 2000; Nachtegaal and Sparks, 2003; Trivedi et al.2003, 2004; Wazne et al. 2003). Qualitative and quantitative information fromspectroscopy can be included in <strong>adsorption</strong> modeling, connecting molecular details tomacroscopic measurements, and resulting in improved modeling of the solid/liquidinterface (e.g., Katz and Hayes, 1995 a, b; Hayes and Katz, 1996; Dyer et al. 2003, 2004).Overall, trace <strong>metal</strong> <strong>adsorption</strong> to mineral surfaces is an important phenomenon inmany industrial applications as well as in the study of the natural environment.Development of better mechanistic <strong>adsorption</strong> models that describe the binding withphysically meaningful species is not only of theoretical but also potentially of greatpractical interest (van Riemsdijk and Hiemstra, 1998). The objective of this proposedresearch is to understand the effect of iron oxides, as discrete particles and coatings, oncontaminant <strong>adsorption</strong>. Surface complexation modeling constrained with XAS data isinvoked for single and binary adsorbate studies. Results of this work assist in betterunderstanding and predicting the mobility and bioavailability of trace <strong>metal</strong>s in soils,sediments, and groundwater.