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Thomas Fanghänel, pfitzner, E. Steinle, J. I. Kim

Thermodynamics of Cm(III) in Concentrated Electrolyte Solutions. Fluoride Complexation in 0–5 m NaCl at 25°C

The fluoride complexation of Cm(III) is investigated by means of time-resolved laser fluorescence spectroscopy (TRLFS) at 25°C. In the first set of experiments, the speciation of Cm(III) is investigated in 1 m NaCl as function of the fluoride concentration (m_F < 8 · 10^–3 m). The monofluoride complex CmF²⁺ is identified and its formation constant is determined to be logb
(CmF²⁺) = 2.46 &plusm; 0.05. At the highest fluoride concentration there is evidence for the formation of a Cm(III) difluoride complex to a small extent. However, as the fluoride concentration interval is limited by the precipitation of CmF₃ (s), the stability constant of CmF²⁺ can not be quantified. In the second set of experiments the formation of CmF²⁺ is studied in 0–5 m NaCl. The ionic strength dependence of the formation constant is described by modeling the activity coefficients with the ion interaction approach (Pitzer equations). The formation constant at I = 0 is calculated to be logb
°(CmF²⁺) = 3.44 &plusm; 0.05.

Radiochimica Acta, Oldenbourg Wissenschaftsverlag

Print ISSN: 0033-8230
Volume: 84, 02/1999
Pages: 85

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