Experimental determination of the solubility constant for magnesium chloride hydroxide hydrate (Mg3Cl(OH)5·4H2O, phase 5) at room temperature, and its importance to nuclear waste isolation in geological repositories in salt formations

Xiong, Yongliang; Deng, Haoran; Nemer, Martin B.; Johnsen, Shelly

doi:10.1016/j.gca.2010.05.029

Cited by 49 publications

(24 citation statements)

References 23 publications

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“…For example, its high thermal conductivity contributes to its use as a stable refractory material [1], and its structure makes it an ideal basic oxide model [2,3]. MgO has also been used for construction [4,5], optics [6,7], medicine [8,9], fertilizers [10], electronics [11,12], catalysis [13], chemical warfare agent decontamination [14], high temperature super conductors [15], hydrogen storage [16,17], and nuclear waste storage [18,19]. For many of these applications, the performance of MgO depends on property reproducibility that may be impacted by impurities or defects formed from the conversion of MgO to other magnesium-containing phases due to environmental exposure.…”

Section: Introductionmentioning

confidence: 99%

Computational and Experimental 1H-NMR Study of Hydrated Mg-Based Minerals

2020

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Magnesium oxide (MgO) can convert to different magnesium-containing compounds depending on exposure and environmental conditions. Many MgO-based phases contain hydrated species allowing 1H-nuclear magnetic resonance (NMR) spectroscopy to be used in the characterization and quantification of proton-containing phases; however, surprisingly limited examples have been reported. Here, 1H-magic angle spinning (MAS) NMR spectra of select Mg-based minerals are presented and assigned. These experimental results are combined with computational NMR density functional theory (DFT) periodic calculations to calibrate the predicted chemical shielding results. This correlation is then used to predict the NMR shielding for a series of different MgO hydroxide, magnesium chloride hydrate, magnesium perchlorate, and magnesium cement compounds to aid in the future assignment of 1H-NMR spectra for complex Mg phases.

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Section: Introductionmentioning

confidence: 99%

Computational and Experimental 1H-NMR Study of Hydrated Mg-Based Minerals

2020

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“…It is thought that compositions bounded between 11≤MgO/MgCl 2 (molar ratio)≤17 provide superior strength and abrasion resistance, as they result in an abundance of P5. While P3 and P5 both contribute to (for mixtures constituted at equivalent solution‐to‐solid ratios by mass), P5 is thought to be more effective at imparting strength due to its rod‐like morphology, high(er) molar volume, and enhanced ability to diminish the porosity . The optimal brine concentrations required to maximize P5 formation are achieved at 12≤H 2 O/MgCl 2 (molar ratio)≤18 .…”

Section: Introductionmentioning

confidence: 99%

“…Other factors such as the magnesium source, the calcination temperature of MgO, and the curing conditions may also affect the reaction kinetics and phase assemblages of hydrated MOCs . While some sources report that P3 and P5 may coexist, P5 is thought to remain stable indefinitely unless contacted by water or CO 2 . Others suggest that P5 ultimately converts to P3 which is thermodynamically more stable .…”

Section: Introductionmentioning

confidence: 99%

The influence of composition and temperature on hydrated phase assemblages in magnesium oxychloride cements

et al. 2017

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Due to their nonhydraulic nature, magnesium oxychloride cements (MOCs) are susceptible to degradation following contact with water. Improving the water resistance of these materials requires better understanding of hydrated phase relations and the sensitivity of hydrated phases to water. Toward this end, a series of targeted experiments and complementary thermodynamic calculations were carried out to assess hydrated phase assemblages in the system MgO-MgCl 2 -H 2 O across a range of compositions. Focus is placed on appraising the effects of composition and reaction temperature. In broad agreement with literature data, under ambient conditions, hydrated MOCs are noted to contain Phase 3 (P3), Phase 5 (P5), and brucite, but the mass partitioning of these phases is highly dependent on H 2 O/ MgCl 2 and MgO/MgCl 2 molar ratio as well as curing temperature and age. At room temperature, P3 is favored at lower water contents, however, P5 and/or brucite are favored to form as water availability increases. Thermodynamic calculations indicate that P3 is "more stable" than P5 at lower temperatures-an outcome which impacts the engineering properties, for example, strength and volume stability. The impacts of the accuracy and self-consistency of currently available thermodynamic data and their implications on predicted phase assemblages are discussed. K E Y W O R D S hydration, magnesium oxychloride cement, mechanical properties, temperature, thermodynamics, volume change Angeles, CA.

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“…Thus, for Mg-Na-Cl-dominated brines such as GWB, formation of phase 5 is expected under repository conditions. Subsequent SNL laboratory work indicates that phase 5, not phase 3, is the stable Mg-Cl-OH phase in Mg-Na-Cl-dominated brines in the presence of periclase or brucite (Xiong et al 2010b).…”

Section: Literature Reviewmentioning

confidence: 99%

Analysis report for WIPP colloid model constraints and performance assessment parameters

Mariner

Sassani

2014

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An analysis of the Waste Isolation Pilot Plant (WIPP) colloid model constraints and parameter values was performed. The focus of this work was primarily on intrinsic colloids, mineral fragment colloids, and humic substance colloids, with a lesser focus on microbial colloids. Comments by the US Environmental Protection Agency (EPA) concerning intrinsic Th(IV) colloids and Mg-Cl-OH mineral fragment colloids were addressed in detail, assumptions and data used to constrain colloid model calculations were evaluated, and inconsistencies between data and model parameter values were identified. This work resulted in a list of specific conclusions regarding model integrity, model conservatism, and opportunities for improvement related to each of the four colloid types included in the WIPP performance assessment.

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Experimental determination of the solubility constant for magnesium chloride hydroxide hydrate (Mg3Cl(OH)5·4H2O, phase 5) at room temperature, and its importance to nuclear waste isolation in geological repositories in salt formations

Cited by 49 publications

References 23 publications

Computational and Experimental 1H-NMR Study of Hydrated Mg-Based Minerals

Computational and Experimental 1H-NMR Study of Hydrated Mg-Based Minerals

The influence of composition and temperature on hydrated phase assemblages in magnesium oxychloride cements

Analysis report for WIPP colloid model constraints and performance assessment parameters

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