EXAFS investigations of erth alkaline metal uranyl tricarbonato complexes


EXAFS investigations of erth alkaline metal uranyl tricarbonato complexes

Amayri, S.; Reich, T.; Bernhard, G.

Carbonate and bicarbonate are the common anions found in significant concentrations in many natural waters, and they are strong complexation agents for actinide ions. Seepage, flooding and mining waters from the uranium mining area in the southeast of Germany (Saxony and Thuringia), contain relatively high amounts of magnesium, calcium, carbonate and sulfate ions. In these waters the pH values range from 7.0 to 8.0 and the uranium content is about 0.02 mmol/L where magnesium, calcium and carbonate concentrations are 11.6 mmol/L, 6.9 mmol/L and 3.9 mmol/L, respectively /1/.
Recently we were able to confirm the existence of the natural complexes Ca2UO2(CO3)3(aq) and Mg2UO2(CO3)3(aq) by spectroscopic measurements /2/.
We performed Extended X-ray Absorption Fine Structure (EXAFS) measurements at the uranium LIII- edge to study the structures of these complexes. The obtained results by EXAFS of these complex solutions are compared with those from the corresponding EXAFS and XRD data related to the secondary minerals of uranium, liebigite, Ca2[UO2(CO3)3]×10H2O and bayleyite, Mg2[UO2(CO3)3]×10H2O and they are in good agreement.

References:

/1/ Bernhard, G., G. Geipel, V. Brendler, H. Nitsche: Uranium speciation in waters of different
uranium mining areas, J. of Alloys and Compounds 201 (1998) 271-273.
/2/ Bernhard, G., G. Geipel, V. Brendler, H. Nitsche: Speciation of Uranium in Seepage Waters of a
Mine Tailing Pile Studied by Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLFS),
Radiochim. Acta 74 (1996), 87-91.

  • Poster
    Eurokonferenz Actinide-XAS-2000, 10.09.-12.09. 2000, Grenoble

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