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Communication dans un congrès

Study of the binary NaOH-H2O system and its extension to two ternary highly concentrated systems (NaOH-NaCl-H2O and NaOH-LiOH-H2O) up to high temperature

Abstract : This study presents a new parameterization of the NaOH-H2O system able to calculate the excess properties (osmotic coefficient, activity coefficient) of electrolyte solutions between 0 and 250°C and for concentrations up to salt saturation (higher than 30 M according to temperature). Two scenarios have been examined using the thermodynamic Pitzer's model [1] : (1) NaOH is treated as fully dissociated; (2) NaOH is partially dissociated and the neutral aqueous species NaOH0(aq) is explicitly introduced in the model. The optimization procedure is gradual, starting with the simplest parametrization before complexing the approach up to satisfactorily representing the excess properties of the solutions. First, the scenario (1) was considered and three parameters (β(0), β(1) et Cϕ) were optimized. Then the parameters β(2) and α2 were optimized. As the results were not fitting the experimental data we moved to the scenario (2) by introducing NaOH0(aq) with two ternary parameters (ζNaOH/Na+/OH- and λNaOH/NaOH) in addition to β(0), β(1) et Cϕ and the thermodynamic equilibrium constant (KNaOH). These parameters have been optimized between 0 and 250°C with experimental measurements of osmotic coefficient and water activity. We also studied the solubility of NaOH in water by determining the thermodynamic solubility products of the five hydrated salts (NaOH:nH2O with n=1, 2, 3.11, 3.5 and 4). The parameterization of the NaOH-H2O system was used, without new adjustment, to predict the boiling point raise of NaOH solutions according to salinity. To finish, we studied two ternary systems (NaOH-NaCl-H2O and NaOH-LiOH-H2O) by adjusting mixture interaction parameters. The model calculates with a high accuracy the properties of these solutions and the solubility of hydrated salts up to high temperature. References [1] K.S. Pitzer, Thermodynamics of electrolytes. I. Theoretical basis and general equations, J. Phys. Chem. 77 (1973) 268-277.
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Communication dans un congrès
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https://hal-brgm.archives-ouvertes.fr/hal-01010097
Contributeur : Adeline Lach <>
Soumis le : jeudi 19 juin 2014 - 11:23:02
Dernière modification le : mardi 9 juin 2020 - 15:00:21

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  • HAL Id : hal-01010097, version 1

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Adeline Lach, Laurent André, Arnault Lassin, Mohamed Azaroual, Jean-Paul Serin, et al.. Study of the binary NaOH-H2O system and its extension to two ternary highly concentrated systems (NaOH-NaCl-H2O and NaOH-LiOH-H2O) up to high temperature. 24ème Réunion des Sciences de la Terre : RST 2014, Oct 2014, Pau, France. ⟨hal-01010097⟩

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