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Title: Thermodynamic Model for the Solubility of NdF3(cr) in the Na+-NH4+ – Nd3+–F-–H2O System at 25 °C

The objectives of this study were to develop a reliable thermodynamic model for the Nd-F system based on critical review and experimental studies. The SIT model was used to convert concentration constants reported in the literature to constants at zero ionic strengths for cross comparison and selection of reliable values. The critically evaluated thermodynamic constants for the formation of NdF2+ and NdF2+ were then used to interpret the extensive NdF3(cr) solubility data in NaF and NH4F solutions, ranging in concentrations from extremely low values to as high as 1.0, equilibrated for different periods ranging up to as long as 72 days. These efforts have resulted in log βn0 for the reaction [Nd3+ + nF- = NdFn</3-n] of (3.81 ± 0.10), (5.89 ± 0.77), and <12.48 for n of 1 through 3, respectively. The log10 Ksp0 for the solubility of NdF3(cr) (NdF3(cr) = Nd3+ + 3F-) was determined to be -(20.49 ± 0.37). Because 1) Nd is an excellent analog for trivalent actinides -- An(III) (e.i., Pu(III), Am(III), and Cm(III)) -- and 2) the available data for the An(III)-F system, especially the solubility products of AnF3(cr), are of extremely poor quality, the critical literature review in combination with the experimentalmore » Nd-F system data have been used to assign thermodynamic constants for the An(III)-F reactions until good quality specific data for them becomes available.« less
 [1] ;  [2] ;  [2] ;  [2] ;  [3]
  1. Rai Enviro-Chem, LLC., Yachats, OR (United States)
  2. Japan Atomic Energy Agency (JAEA), Tokai (Japan)
  3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0095-9782; KP1702030
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solution Chemistry; Journal Volume: 42; Journal Issue: 7
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY solubility; neodymium; fluoride complexes of Nd; solubility product; thermodynamic data; NdF2+; NdF2+; NdF39cr); Nd(OH)3(aq)