Change search
ReferencesLink to record
Permanent link

Direct link
Removal of uranium(VI) from the aqueous phase by iron(II) minerals in presence of bicarbonate
KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
Show others and affiliations
2009 (English)In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 24, no 9, 1617-1625 p.Article in journal (Refereed) Published
Abstract [en]

Uranium(VI) mobility in groundwater is strongly affected by sorption of mobile U(VI) species (e.g. uranyl, UO22+) to mineral surfaces, precipitation of U(VI) compounds, such as schoepite (UO2)(4)O(OH)(6)center dot 6H(2)O), and by reduction to U(IV), forming sparingly soluble phases (uraninite; UO2). The latter pathway, in particular, would be very efficient for long-term immobilization of U. In nature, Fe(II) is an important reducing agent for U(VI) because it frequently occurs either dissolved in natural waters, sorbed to matrix minerals, or structurally bound in many minerals. Redox reactions between U(VI) and Fe(II) depend not only on the availability of Fe(II) in the environment, but also on the chemical conditions in the aqueous solution. Under natural groundwater condition U(VI) forms complexes with many anionic ligands, which strongly affect its speciation. Carbonate, in particular, is known to form stable complexes with U, raising the question, if U(VI), when complexed by carbonate, can be reduced to UO2. The goal of this study was to find out if Fe(II) when structurally bound in a mineral (as magnetite, Fe3O4) or sorbed to a mineral surface (as corundum, Al2O3) can reduce U(VI) to U(IV) in the presence of HCO3-. Batch experiments were conducted under anaerobic conditions to observe U removal from the aqueous phase by the two minerals depending on HCO3- addition (1 mM), U concentration (0.01-30 mu M) and pH value (6-10). Immediately after the experiments, the mineral surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) to obtain information on the redox state of U bound to the solid surfaces. XPS results gave evidence that U(VI) can be reduced both by magnetite and by corundum amended with Fe(II). In the presence of HCO3 the amount of reduced U on the mineral surfaces increased compared to carbonate-free solutions. This can be explained by the formation of Fe(II) carbonates on the mineral surfaces which represent an easily available Fe(II) pool for the U(VI) reduction. A facilitated U(VI) reduction is also considered possible when U is present as a carbonate complex compared to non-complexed U (e.g. uranyl).

Place, publisher, year, edition, pages
2009. Vol. 24, no 9, 1617-1625 p.
Keyword [en]
hematite particles, reduction, magnetite, surface, uranyl, equilibria, complexes, sorption, fe(ii), u(vi)
URN: urn:nbn:se:kth:diva-18851DOI: 10.1016/j.apgeochem.2009.04.029ISI: 000270644900001ScopusID: 2-s2.0-68949216341OAI: diva2:336898
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-01-18Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Regenspurg, SimonaMalmström, Maria E.
By organisation
Industrial Ecology
In the same journal
Applied Geochemistry

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 29 hits
ReferencesLink to record
Permanent link

Direct link