Challenges in Detection, Structural Characterization and Determination of Complex Formation Constants of Uranyl-Arsenate Complexes in Aqueous Solutions

  • Wondemagegnehu A. Gezahegne
  • Christoph Hennig
  • Gerhard Geipel
  • Britta Planer-Friedrich
  • Broder J. Merkel
Part of the Springer Geology book series (SPRINGERGEOL)


Uranium forms analogous minerals with phosphate and arsenate. In aqueous solutions an analogy is expected to govern the complexes that uranium builds with these ligands. Three uranyl arsenate complexes UO2H2AsO4+, UO2HAsO40 and UO2(H2AsO4)20 were identified and reported previously with TRLFS in the pH range 1 to 3. Using a similar detection system and elevating the pH range a negatively charged fourth uranyl-arsenate complex, UO2AsO4 was found under circum neutral pH. Determining the complex formation constant for this complex was not possible due to the susceptibility of the fluorescence intensity to external influences and the difficulty of resolving the measured spectra into individual fluorescence contributions. By immediate shock-freezing to 15 K we succeeded to measure a reproducible EXAFS spectrum of a uranyl-arsenate species in an aqueous solution at pH 2.


Fluorescence Lifetime Uranium Concentration EXAFS Spectrum Complex Formation Constant Uranium Speciation 
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© Springer-Verlag Berlin Heidelberg 2011

Authors and Affiliations

  • Wondemagegnehu A. Gezahegne
    • 1
  • Christoph Hennig
    • 2
  • Gerhard Geipel
    • 2
  • Britta Planer-Friedrich
    • 3
  • Broder J. Merkel
    • 1
  1. 1.Department of Geology, Chair of HydrogeologyTechnische Universität Bergakademie FreibergFreibergGermany
  2. 2.Institute of RadiochemistryHelmholtz-Zentrum Dresden-RossendorfDresdenGermany
  3. 3.Environmental GeochemistryBayreuth UniversityBayreuthGermany

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