Solid-liquid equilibria of Sorel phases and Mg (OH)2 in the system Na-Mg-Cl-OH-H2O. Part I: experimental determination of OH− and H+ equilibrium concentrations and solubility constants at 25°C, 40°C, and 60°C
Sorel phases are the binder phases of the magnesia building material (Sorel cement/concrete) and of special concern for the construction of long-term stable geotechnical barriers in repositories for radioactive waste in rock salt, as potentially occurring brines are expected to contain MgCl2. Sorel...
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Frontiers Media S.A.
2023-05-01
|
| Series: | Frontiers in Nuclear Engineering |
| Subjects: | |
| Online Access: | https://www.frontiersin.org/articles/10.3389/fnuen.2023.1188789/full |
| _version_ | 1797815122568151040 |
|---|---|
| author | Melanie Pannach Iris Paschke Volker Metz Marcus Altmaier Wolfgang Voigt Daniela Freyer |
| author_facet | Melanie Pannach Iris Paschke Volker Metz Marcus Altmaier Wolfgang Voigt Daniela Freyer |
| author_sort | Melanie Pannach |
| collection | DOAJ |
| description | Sorel phases are the binder phases of the magnesia building material (Sorel cement/concrete) and of special concern for the construction of long-term stable geotechnical barriers in repositories for radioactive waste in rock salt, as potentially occurring brines are expected to contain MgCl2. Sorel phases, in addition to Mg(OH)2, are equally important as pH buffers to minimize solubility and potential mobilization of radionuclides in brine systems. In order to obtain a detailed database of the relevant solid-liquid equilibria and the related pHm values of the equilibrium solutions, extensive experimental investigations were carried out. Solid phase formation was studied by suspending MgO and Mg(OH)2 in NaCl saturated MgCl2-solutions at 25°C. Mg(OH)2 and the 3-1-8 Sorel phase were identified as the stable solid phases, while the 5-1-8 Sorel phase is metastable. Equilibration at 40°C did not lead to any solid phase changes. Both OH− and H+ equilibrium concentrations were analyzed as a function of MgCl2 concentration at 25°C and 40°C. In addition to our already published solid-liquid equilibria for the ternary system Mg-Cl-OH-H2O (25°C–120°C), the equilibrium H+ concentrations (pHm) determined at 25°C, 40°C and 60°C are now reported. Analyzing these data together with known ion-interaction Pitzer coefficients, the solubility constants for Mg(OH)2 and the 3-1-8 phase at these three temperatures, for the metastable 5-1-8 phase at 25°C and for the 2-1-4 phase at 60°C have been consistently calculated. |
| first_indexed | 2024-03-13T08:18:01Z |
| format | Article |
| id | doaj.art-b689211072854cbcb30025a6e7b1a07a |
| institution | Directory Open Access Journal |
| issn | 2813-3412 |
| language | English |
| last_indexed | 2024-03-13T08:18:01Z |
| publishDate | 2023-05-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Nuclear Engineering |
| spelling | doaj.art-b689211072854cbcb30025a6e7b1a07a2023-05-31T13:25:09ZengFrontiers Media S.A.Frontiers in Nuclear Engineering2813-34122023-05-01210.3389/fnuen.2023.11887891188789Solid-liquid equilibria of Sorel phases and Mg (OH)2 in the system Na-Mg-Cl-OH-H2O. Part I: experimental determination of OH− and H+ equilibrium concentrations and solubility constants at 25°C, 40°C, and 60°CMelanie Pannach0Iris Paschke1Volker Metz2Marcus Altmaier3Wolfgang Voigt4Daniela Freyer5TU Bergakademie Freiberg, Institut für Anorganische Chemie (TU BAF), Freiberg, GermanyTU Bergakademie Freiberg, Institut für Anorganische Chemie (TU BAF), Freiberg, GermanyKarlsruher Institut für Technologie, Institut für Nukleare Entsorgung (KIT-INE), Karlsruhe, GermanyKarlsruher Institut für Technologie, Institut für Nukleare Entsorgung (KIT-INE), Karlsruhe, GermanyTU Bergakademie Freiberg, Institut für Anorganische Chemie (TU BAF), Freiberg, GermanyTU Bergakademie Freiberg, Institut für Anorganische Chemie (TU BAF), Freiberg, GermanySorel phases are the binder phases of the magnesia building material (Sorel cement/concrete) and of special concern for the construction of long-term stable geotechnical barriers in repositories for radioactive waste in rock salt, as potentially occurring brines are expected to contain MgCl2. Sorel phases, in addition to Mg(OH)2, are equally important as pH buffers to minimize solubility and potential mobilization of radionuclides in brine systems. In order to obtain a detailed database of the relevant solid-liquid equilibria and the related pHm values of the equilibrium solutions, extensive experimental investigations were carried out. Solid phase formation was studied by suspending MgO and Mg(OH)2 in NaCl saturated MgCl2-solutions at 25°C. Mg(OH)2 and the 3-1-8 Sorel phase were identified as the stable solid phases, while the 5-1-8 Sorel phase is metastable. Equilibration at 40°C did not lead to any solid phase changes. Both OH− and H+ equilibrium concentrations were analyzed as a function of MgCl2 concentration at 25°C and 40°C. In addition to our already published solid-liquid equilibria for the ternary system Mg-Cl-OH-H2O (25°C–120°C), the equilibrium H+ concentrations (pHm) determined at 25°C, 40°C and 60°C are now reported. Analyzing these data together with known ion-interaction Pitzer coefficients, the solubility constants for Mg(OH)2 and the 3-1-8 phase at these three temperatures, for the metastable 5-1-8 phase at 25°C and for the 2-1-4 phase at 60°C have been consistently calculated.https://www.frontiersin.org/articles/10.3389/fnuen.2023.1188789/fullsolubility equilibriumsystem Na-Mg-Cl-OH-H2Osystem Mg-Cl-OH-H2Omagnesium oxychlorideSorel phasesMg(OH)2 |
| spellingShingle | Melanie Pannach Iris Paschke Volker Metz Marcus Altmaier Wolfgang Voigt Daniela Freyer Solid-liquid equilibria of Sorel phases and Mg (OH)2 in the system Na-Mg-Cl-OH-H2O. Part I: experimental determination of OH− and H+ equilibrium concentrations and solubility constants at 25°C, 40°C, and 60°C Frontiers in Nuclear Engineering solubility equilibrium system Na-Mg-Cl-OH-H2O system Mg-Cl-OH-H2O magnesium oxychloride Sorel phases Mg(OH)2 |
| title | Solid-liquid equilibria of Sorel phases and Mg (OH)2 in the system Na-Mg-Cl-OH-H2O. Part I: experimental determination of OH− and H+ equilibrium concentrations and solubility constants at 25°C, 40°C, and 60°C |
| title_full | Solid-liquid equilibria of Sorel phases and Mg (OH)2 in the system Na-Mg-Cl-OH-H2O. Part I: experimental determination of OH− and H+ equilibrium concentrations and solubility constants at 25°C, 40°C, and 60°C |
| title_fullStr | Solid-liquid equilibria of Sorel phases and Mg (OH)2 in the system Na-Mg-Cl-OH-H2O. Part I: experimental determination of OH− and H+ equilibrium concentrations and solubility constants at 25°C, 40°C, and 60°C |
| title_full_unstemmed | Solid-liquid equilibria of Sorel phases and Mg (OH)2 in the system Na-Mg-Cl-OH-H2O. Part I: experimental determination of OH− and H+ equilibrium concentrations and solubility constants at 25°C, 40°C, and 60°C |
| title_short | Solid-liquid equilibria of Sorel phases and Mg (OH)2 in the system Na-Mg-Cl-OH-H2O. Part I: experimental determination of OH− and H+ equilibrium concentrations and solubility constants at 25°C, 40°C, and 60°C |
| title_sort | solid liquid equilibria of sorel phases and mg oh 2 in the system na mg cl oh h2o part i experimental determination of oh and h equilibrium concentrations and solubility constants at 25°c 40°c and 60°c |
| topic | solubility equilibrium system Na-Mg-Cl-OH-H2O system Mg-Cl-OH-H2O magnesium oxychloride Sorel phases Mg(OH)2 |
| url | https://www.frontiersin.org/articles/10.3389/fnuen.2023.1188789/full |
| work_keys_str_mv | AT melaniepannach solidliquidequilibriaofsorelphasesandmgoh2inthesystemnamgclohh2opartiexperimentaldeterminationofohandhequilibriumconcentrationsandsolubilityconstantsat25c40cand60c AT irispaschke solidliquidequilibriaofsorelphasesandmgoh2inthesystemnamgclohh2opartiexperimentaldeterminationofohandhequilibriumconcentrationsandsolubilityconstantsat25c40cand60c AT volkermetz solidliquidequilibriaofsorelphasesandmgoh2inthesystemnamgclohh2opartiexperimentaldeterminationofohandhequilibriumconcentrationsandsolubilityconstantsat25c40cand60c AT marcusaltmaier solidliquidequilibriaofsorelphasesandmgoh2inthesystemnamgclohh2opartiexperimentaldeterminationofohandhequilibriumconcentrationsandsolubilityconstantsat25c40cand60c AT wolfgangvoigt solidliquidequilibriaofsorelphasesandmgoh2inthesystemnamgclohh2opartiexperimentaldeterminationofohandhequilibriumconcentrationsandsolubilityconstantsat25c40cand60c AT danielafreyer solidliquidequilibriaofsorelphasesandmgoh2inthesystemnamgclohh2opartiexperimentaldeterminationofohandhequilibriumconcentrationsandsolubilityconstantsat25c40cand60c |