Experimental stability of magnesium sulfate hydrates that may be present on Mars

Chipera, S. J.; Vaniman, D. T.

doi:10.1016/j.gca.2006.07.044

Cited by 147 publications

(205 citation statements)

References 39 publications

(48 reference statements)

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“…7 Also, the hydrates of MgCl 2 appear to be noncomplex without the presence of any unusual low energy isomers. This difference in the influence of hydrogen bonds to form meta-stable states may possibly be regarded as the reason for the faster hydration kinetics in MgCl 2 as observed by Ferchaud et al 41 in comparison with MgSO 4 .…”

Section: Resultsmentioning

confidence: 86%

“…The crystal structure, surface defects and dislocations present in these hydrates significantly influence the hydration/dehydration kinetics. 3 The MgSO 4 hydrates are known to exhibit slow kinetics, arguably due to the presence of metastable states, 4 whereas the hygroscopic magnesium chloride generally undergoes faster hydration and dehydration reactions, essentially increasing the power output in a seasonal energy storage system. However, the dehydration of MgCl 2 hydrates is usually accompanied by a hydrolysis 5 reaction with the release of HCl, which can potentially damage the material as well as the equipment.…”

Section: Introductionmentioning

confidence: 99%

“…Molecular structures of MgSO 4 hydrates have been subject of investigation in the literature, [6][7][8][9][10][11][12][13] especially the presa) Electronic mail: s.v.nedea@tue.nl ence of strong hydrogen bond networks catalyzing the formation of meta-stable states. 6,7,14 However, fewer accounts exist on the molecular structure of MgCl 2 hydrates.…”

Section: Introductionmentioning

confidence: 99%

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A DFT based equilibrium study on the hydrolysis and the dehydration reactions of MgCl2 hydrates

Iype

Nedea

Rindt

2013

The Journal of Chemical Physics

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Magnesium chloride hydrates are characterized as promising energy storage materials in the built-environment. During the dehydration of these materials, there are chances for the release of harmful HCl gas, which can potentially damage the material as well as the equipment. Hydrolysis reactions in magnesium chloride hydrates are subject of study for industrial applications. However, the information about the possibility of hydrolysis reaction, and its preference over dehydration in energy storage systems is still ambiguous at the operating conditions in a seasonal heat storage system. A density functional theory level study is performed to determine molecular structures, charges, and harmonic frequencies in order to identify the formation of HCl at the operating temperatures in an energy storage system. The preference of hydrolysis over dehydration is quantified by applying thermodynamic equilibrium principles by calculating Gibbs free energies of the hydrated magnesium chloride molecules. The molecular structures of the hydrates (n = 0, 1, 2, 4, and 6) of MgCl2 are investigated to understand the stability and symmetry of these molecules. The structures are found to be noncomplex with almost no meta-stable isomers, which may be related to the faster kinetics observed in the hydration of chlorides compared to sulfates. Also, the frequency spectra of these molecules are calculated, which in turn are used to calculate the changes in Gibbs free energy of dehydration and hydrolysis reactions. From these calculations, it is found that the probability for hydrolysis to occur is larger for lower hydrates. Hydrolysis occurring from the hexa-, tetra-, and di-hydrate is only possible when the temperature is increased too fast to a very high value. In the case of the mono-hydrate, hydrolysis may become favorable at high water vapor pressure and at low HCl pressure.

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Section: Resultsmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A DFT based equilibrium study on the hydrolysis and the dehydration reactions of MgCl2 hydrates

Iype

Nedea

Rindt

2013

The Journal of Chemical Physics

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“…Aqueous MgSO 4 solutions have been studied extensively at ambient pressure, P, as a function of temperature, T . In an early work, Noyes et al 7 related the electrical conductivity of aqueous MgSO 4 fluids to their degree of ionization.…”

Section: Introductionmentioning

confidence: 99%

“…Studies using ultrasonic absorption and dielectric relaxation spectroscopies have shown the simultaneous existence of different associated species 10,11 , which according to the association model of Eigen and Tamm 10 are the double solvent separated ion pair (2SIP), Mg(H 2 O) 2 SO 4 (aq), the solvent separated ion pair (SIP), Mg(H 2 O)SO 4 (aq), and the contact ion pair (CIP), MgSO 4 (aq). For concentrated solutions (>1 molal), triple ions (TI), e.g.…”

Section: Introductionmentioning

confidence: 99%

Speciation in Aqueous MgSO₄Fluids at High Pressures and High Temperatures from ab Initio Molecular Dynamics and Raman Spectroscopy

Jahn

Schmidt

2010

J. Phys. Chem. B

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Ab initio molecular dynamics simulations and in situ Raman spectroscopy are used to study the speciation in two molal aqueous MgSO 4 solutions at high pressures, P, and temperatures, T. While at ambient conditions the fluid is dominated by dissociated SO 4 2-(aq) ions and solvent-separated ion pairs, ion association strongly increases with increasing temperature and pressure along a 1.33 g/cm 3 isochore. At T ) 450 °C and P ) 1.4 GPa, the ν 1 (SO 4 2-) Raman band is well described by three Gaussian + Lorentzian components of about equal intensity with peaks at about 980, 995, and 1005 cm -1 . Analysis of the simulations, however, indicates the coexistence of more than three species, including dissociated SO 4 2-(aq) ions, and contact and triple ion pairs as well as larger complexes. In addition, the sulfate groups may be bonded to Mg as monodentate or bidentate ligands. The frequencies of the associated species seem to depend mainly on the type and number of Mg-SO 4 bonds. We interpret the two rather broad high-frequency Raman components as a single "Mg-SO 4 contact" component with variable frequency distribution. As a consequence, the ν 1 (SO 4 2-) Raman band provides only information on the molecular environment of the sulfate group; i.e., individual species cannot be resolved. At fluid densities less than about 1.2 g/cm 3 and temperatures above 400 °C, the formation of HSO 4 -(aq)containing species is observed in both simulations and experiments, which may be accompanied by a change in pH and electrical conductivity.

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The spectral variability of kieserite (MgSO₄·H₂O) with temperature and grain size and its application to the Martian surface

et al. 2014

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We spectrally characterize (λ = 0.35-10 μm) the low-humidity polymorph of kieserite (MgSO 4 ·H 2 O), which is abundant on Mars and likely present on Europa, at various grain sizes and temperatures (100-300 K) relevant to the surfaces of Mars and Europa. Compositional analysis of these surfaces often relies on remote sensing using imaging spectrometers such as Mars Reconnaissance Orbiter Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), Mars Express Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité, and Galileo Near-Infrared Mapping Spectrometer. To estimate surface abundances from these observations, well-characterized laboratory spectra are required for comparison. Several variables, including temperature and grain size, affect the observed spectra and must be quantified in the laboratory to more confidently evaluate the returned data. Certain spectral features of kieserite exhibit predictable variability with changes in temperature and grain size that may be exploited to better understand the nature of kieserite on the surface of Mars. For instance, trends in our spectral analysis suggest that absorption features centered at λ < 3.0 μm were primarily sensitive to temperature changes, while features at λ > 3.0 μm were additionally sensitive to grain size changes. We compare our laboratory spectra with selected CRISM data of suspected Martian kieserite and assess the inherent uncertainty that exists in using band center minima to determine surface composition. Incorporation of these temperature and grain size-specific spectra into linear mixture models of planetary surface spectra will improve the compositional interpretation and contribute to our understanding of surface geochemistry and chemical evolution.

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Experimental stability of magnesium sulfate hydrates that may be present on Mars

Cited by 147 publications

References 39 publications

A DFT based equilibrium study on the hydrolysis and the dehydration reactions of MgCl2 hydrates

A DFT based equilibrium study on the hydrolysis and the dehydration reactions of MgCl2 hydrates

Speciation in Aqueous MgSO₄Fluids at High Pressures and High Temperatures from ab Initio Molecular Dynamics and Raman Spectroscopy

The spectral variability of kieserite (MgSO₄·H₂O) with temperature and grain size and its application to the Martian surface

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Experimental stability of magnesium sulfate hydrates that may be present on Mars

Cited by 147 publications

References 39 publications

A DFT based equilibrium study on the hydrolysis and the dehydration reactions of MgCl2 hydrates

A DFT based equilibrium study on the hydrolysis and the dehydration reactions of MgCl2 hydrates

Speciation in Aqueous MgSO4Fluids at High Pressures and High Temperatures from ab Initio Molecular Dynamics and Raman Spectroscopy

The spectral variability of kieserite (MgSO4·H2O) with temperature and grain size and its application to the Martian surface

Contact Info

Product

Resources

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Speciation in Aqueous MgSO₄Fluids at High Pressures and High Temperatures from ab Initio Molecular Dynamics and Raman Spectroscopy

The spectral variability of kieserite (MgSO₄·H₂O) with temperature and grain size and its application to the Martian surface