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Media type:
E-Article
Title:
Solid–liquid equilibria of Sorel phases and Mg(OH)2 in the system Na-Mg-Cl-OH-H2O. Part II: Pitzer modeling
Contributor:
Freyer, Daniela;
Pannach, Melanie;
Voigt, Wolfgang
imprint:
Frontiers Media SA, 2023
Published in:Frontiers in Nuclear Engineering
Language:
Not determined
DOI:
10.3389/fnuen.2023.1236544
ISSN:
2813-3412
Origination:
Footnote:
Description:
<jats:p>For geochemical calculations of solubility equilibria between Sorel phases, Mg(OH)<jats:sub>2</jats:sub>, and oceanic salt solutions, the polythermal THEREDA dataset (based on the HMW model at 25°C) was extended. With both models, H<jats:sup>+</jats:sup> solution concentrations in equilibrium with Mg(OH)<jats:sub>2</jats:sub>(s) and the 3-1-8 Sorel phase at 25°C can be calculated in good agreement. In contrast, calculated OH<jats:sup>−</jats:sup> solution concentrations do not agree. Using the solubility constants (lg K<jats:italic>s</jats:italic>) determined up to 60°C in Part I of this work, together with available solubility isotherms up to 120°C, temperature functions for the 3-1-8 phase (25°C–100°C), 2-1-4 phase (60°C–120°C), and 9-1-4 phase (100°C–120°C) were derived. In order to accurately model the OH<jats:sup>−</jats:sup> solution concentrations, it was necessary to implement the solution species Mg<jats:sub>3</jats:sub>(OH)<jats:sub>4</jats:sub><jats:sup>2+</jats:sup> (∆<jats:sub>R</jats:sub><jats:italic>G</jats:italic><jats:sub><jats:italic>m</jats:italic></jats:sub>° temperature function) in addition to the MgOH<jats:sup>+</jats:sup> already contained in the previous model. Finally, fitting Pitzer mixing coefficients for both species now allow the calculation of the solubility equilibria of Mg(OH)<jats:sub>2</jats:sub>(s) and the Sorel phases in agreement with the experimental data in the Mg-Cl-OH-H<jats:sub>2</jats:sub>O and Na-Mg-Cl-OH-H<jats:sub>2</jats:sub>O systems.</jats:p>