An experimental study of hydroxylbastnasite solubility in aqueous solutions at 25 °C

Martin Voigt*, Juan Diego Rodriguez-Blanco, Beatriz Vallina, Liane G. Benning, Eric H. Oelkers

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


The mobility of rare earth elements (REEs) in natural aqueous solutions is of increasing interest due to their application in numerous high-tech and renewable energy technologies (e.g., wind turbines and electric vehicles), as well as their role as tracers in the Earth Sciences. Basic thermodynamic data for water-rock interactions are, however, sparse and partially inconsistent, even for carbonate minerals of the bastnasite group (REE(CO3)(OH,F)), which currently represent the most exploited REE ore. Towards the improved quantification of the REE in natural and industrial systems, pure hexagonal hydroxylbastnasite and orthorhombic kozoite (REE(CO3)(OH)) were synthesized at hydrothermal conditions and subsequently used as starting material for aqueous dissolution and precipitation experiments. All closed system experiments were performed in air equilibrated aqueous fluids. Reaction progress was followed by measuring pH and REE concentrations at regular intervals. Experiments at 25 °C in the presence of selected concentrations of HCl and NaOH were run for up to 33 days until steady-state pH and REE concentrations were attained. Results indicate that the solubility products (KSP) of the reaction REE(CO3)(OH) = REE3+ + CO32- + OH- are log(KSP) = -23.8 ± 0.1, -24.1 ± 0.3, and -22.3 ± 0.2 for Nd-, La-hydroxylbastnasite, and Nd-kozoite, respectively at 25 °C.

Original languageEnglish
Pages (from-to)70-77
Number of pages8
JournalChemical Geology
Publication statusPublished - 15 Jul 2016

Bibliographical note

Funding Information:
This research was supported by the European Union FP7 Marie Curie Actions Initial Training Network CO2-REACT ( 317235 ). The authors would like to thank Frederic Candaudap and Aurélie Lanzanova for assistance with ICP-MS measurements, as well as Thierry Aigouy and Michel Thibaut for help with SEM- and XRD-measurements, respectively.

Publisher Copyright:
© 2016 Elsevier B.V.

Other keywords

  • Bastnasite
  • Carbonate
  • Kozoite
  • Rare earth elements
  • Solubility
  • Thermodynamics


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