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Binding of iron(III) to organic soils: EXAFS spectroscopy and chemical equilibrium modeling
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.ORCID iD: 0000-0001-8771-7941
2007 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 41, no 4, 1232-1237 p.Article in journal (Refereed) Published
Abstract [en]

The complexation of iron(III) to soil organic matter is important for the binding of trace metals in natural environments because of competition effects. In this study, we used extended X-ray absorption fine structure (EXAFS) spectroscopy to characterize the binding mode for iron(III) in two soil samples from organic mor layers, one of which was also treated with iron(III). In most cases the EXAFS spectra had three significant contributions, inner-core Fe-O/N interactions at about 2.02(2) A, Fe-C interactions in the second scattering shell at 3.00(4) A, and a mean Fe-Fe distance at 3.37(3) A. One untreated sample showed features typical for iron (hydr)oxides; however, after treatment of iron(III) the EXAFS spectrum was dominated by organically complexed iron. The presence of a Fe-Fe distance in all samples showed that the major part of the organically complexed iron was hydrolyzed, most likely in a mixture of complexes with an inner core of (O5Fe)(2)O and (O5Fe)(3)O. These results were used to constrain a model for metal-humic complexation, the Stockholm Humic Model (SHM). The model was able to describe iron(III) binding very well at low pH considering only one dimeric iron(III)-humic complex. The competition effect on trace metals was also well described.

Place, publisher, year, edition, pages
2007. Vol. 41, no 4, 1232-1237 p.
Keyword [en]
ray-absorption spectroscopy, body distribution-functions, humic substances, condensed matter, ion-binding, complexation, iron, ligands, fe(iii), donnan
URN: urn:nbn:se:kth:diva-16378DOI: 10.1021/es0615730ISI: 000244161600030ScopusID: 2-s2.0-33847243016OAI: diva2:334420
QC 20100525Available from: 2010-08-05 Created: 2010-08-05Bibliographically approved

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