Inorganic Ligand Effects on Pb(II) Sorption to Goethite (α-FeOOH): II. Sulfate

✍ Scribed by John D. Ostergren; Gordon E. Brown Jr.; George A. Parks; Per Persson

• Book ID: 102581984
• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 317 KB
• Volume: 225
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1999.6702

✦ Synopsis

The effects of sulfate anions on the uptake of Pb(II) onto goethite were investigated at the molecular level using in situ Pb L(III)-EXAFS and ATR-FTIR spectroscopies. Macroscopic uptake data show that Pb uptake can be enhanced by at least 30% at pH 5 in the presence of 3.16 mM sulfate and that sulfate uptake at pH 7 can be enhanced by more than a factor of 3 in the presence of 1.0 mM Pb. Consistent with behavior in sulfate-free systems, Pb(II) forms inner-sphere complexes sharing either corners or edges with Fe(O,OH)(6) octahedra under all conditions studied. The relative fraction of corner-sharing complexes is, however, significantly enhanced in the presence of sulfate at pH 5, 6, and 7 (all conditions studied) and additional sulfate species with C(3v) or lower point symmetry were noted in the presence of Pb by ATR-FTIR. Drawing on bond valence and structural constraints developed in J. D. Ostergren et al. (2000, J. Colloid Interface Science 224, 000-000), these results indicate formation of Type A ternary complexes bonded to the surface through Pb that is bound as a bridging bidenate complex to two adjacent A-type (singly coordinated) surface oxygens (( identical withFe-O)(2)-Pb-OSO(3)). Copyright 2000 Academic Press.