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Title: Solubility constants of hydroxyl sodalite at elevated temperatures evaluated from hydrothermal experiments: Applications to nuclear waste isolation

In this study, solubility constants of hydroxyl sodalite (ideal formula, Na 8[Al 6Si 6O 24][OH] 2·3H 2O) from 25°C to 100°C are obtained by applying a high temperature Al—Si Pitzer model to evaluate solubility data on hydroxyl sodalite in high ionic strength solutions at elevated temperatures. A validation test comparing model-independent experimental data to model predictions demonstrates that the solubility values produced by the model are in excellent agreement with the experimental data. In addition, the equilibrium constants obtained in this study have a wide range of applications, including synthesis of hydroxyl sodalite, de-silication in the Bayer process for extraction of alumina, and the performance of proposed sodalite waste forms in geological repositories in various lithologies including salt formations. The thermodynamic calculations based on the equilibrium constants obtained in this work indicate that the solubility products in terms of m ΣAl×m ΣSi for hydroxyl sodalite are very low (e.g., ~10 -13 [mol·kg -1] 2 at 100°C) in brines characteristic of salt formations, implying that sodalite waste forms would perform very well in repositories located in salt formations. Finally, the information regarding the solubility behavior of hydroxyl sodalite obtained in this study provides guidance to investigate the performance of other puremore » end-members of sodalite such as chloride- and iodide-sodalite, which may be of interest for geological repositories in various media.« less
  1. Sandia National Laboratories, Carlsbad Programs Group, Carlsbad, NM (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0883-2927; PII: S0883292716303183
Grant/Contract Number:
AC04-94AL85000; SAND2016-2300J
Accepted Manuscript
Journal Name:
Applied Geochemistry
Additional Journal Information:
Journal Volume: 74; Journal Issue: C; Journal ID: ISSN 0883-2927
Research Org:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE); USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 58 GEOSCIENCES; Pitzer model; Nuclear waste disposal; Salt formations
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1396613