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Title: An experimental study of the solubility and speciation of thorium in chloride-bearing aqueous solutions at temperatures up to 250 °C

Journal Article · · Geochimica et Cosmochimica Acta
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [2];  [3];  [4];  [4]; ORCiD logo [2]; ORCiD logo [2]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); McGill Univ., Montreal, QC (Canada)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Washington State Univ., Pullman, WA (United States)
  4. McGill Univ., Montreal, QC (Canada)
+ Show Author Affiliations

In this study, the solubility and speciation of Th in Cl-bearing solutions saturated in ThO2 was investigated experimentally at 150, 175, 200, 225 and 250°C, and saturated water vapor pressure. At these experimental conditions (pH25°C < 3.8, mNaCl < 2.5), Th-chloride complexation is insignificant, and the solubility of Th is controlled by hydrolysis. The two main species in solution were identified as Th(OH)22+ and Th(OH)4° and formed via the reactions Th4+ + 2OH- ↔ Th(OH)$$2+\atop{2}$$ and Th4+ + 4OH- ↔ Th(OH)$$0\atop{4}$$. The logarithms of the formation constants determined for the first reaction are 23.91 ± 0.05, 24.79 ± 0.07, 25.78 ± 0.05, and 25.85 ± 0.05 for 175, 200, 225 and 250°C, respectively, and 42.18 ± 0.06, 43.50 ± 0.07, 43.17 ± 0.08, and 43.74 ± 0.11 for the second reaction at the same temperatures. Formation constants could not be determined reliably for 150 °C. Extrapolations of our formation constants to 25°C are in excellent agreement with the values determined at 25 °C by Neck and Kim (2001) and Ekberg et al. (2000). Finally, for natural systems buffered by thorianite (ThO2), the solubility determined in our study likely reflects a minimum, as the presence of additional ligands would lead to higher solubility.

Research Organization:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Organization:
USDOE Laboratory Directed Research and Development (LDRD) Program
Grant/Contract Number:
AC52-06NA25396; 20180007DR; 20180475DR
OSTI ID:
1467337
Alternate ID(s):
OSTI ID: 1724303
Report Number(s):
LA-UR-18-22200
Journal Information:
Geochimica et Cosmochimica Acta, Vol. 239, Issue C; ISSN 0016-7037
Publisher:
The Geochemical Society; The Meteoritical SocietyCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 19 works
Citation information provided by
Web of Science

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Cited By (2)

The Petyayan-Vara Carbonatite-Hosted Rare Earth Deposit (Vuoriyarvi, NW Russia): Mineralogy and Geochemistry journal January 2020
Challenging the thorium-immobility paradigm journal November 2019

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
58 GEOSCIENCES
thorium
hydrothermal
chloride
hydroxyl