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Solid–liquid equilibria of Sorel phases and Mg(OH)2 in the system Na-Mg-Cl-OH-H2O. Part II: Pitzer modeling
Ist Teil von
Frontiers in nuclear engineering, 2023-09, Vol.2
Ort / Verlag
Frontiers Media S.A
Erscheinungsjahr
2023
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
For geochemical calculations of solubility equilibria between Sorel phases, Mg(OH)
2
, and oceanic salt solutions, the polythermal THEREDA dataset (based on the HMW model at 25°C) was extended. With both models, H
+
solution concentrations in equilibrium with Mg(OH)
2
(s) and the 3-1-8 Sorel phase at 25°C can be calculated in good agreement. In contrast, calculated OH
−
solution concentrations do not agree. Using the solubility constants (lg K
s
) 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
−
solution concentrations, it was necessary to implement the solution species Mg
3
(OH)
4
2+
(∆
R
G
m
° temperature function) in addition to the MgOH
+
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)
2
(s) and the Sorel phases in agreement with the experimental data in the Mg-Cl-OH-H
2
O and Na-Mg-Cl-OH-H
2
O systems.