Thermodynamics and dehydration/hydration behaviors of Na-sulfate, -borate, and -bicarbonate minerals

Tingting Liu; David L. Bish

doi:10.1016/j.tca.2020.178759

Thermodynamics and dehydration/hydration behaviors of Na-sulfate, -borate, and -bicarbonate minerals

Tingting Liu, David L. Bish

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Abstract

Detailed thermal experiments using relative humidity- (RH) and temperature-controlled X-ray diffraction (XRD) and H₂O adsorption/desorption measurements were applied to understand the dehydration/hydration behaviors of thenardite/mirabilite (Na₂SO₄/Na₂SO₄·10H₂O), tincalconite/borax (Na₂B₄O₇·5H₂O/Na₂B₄O₇·10H₂O), nahcolite (NaHCO₃), and qilianshanite (NaH₄ (BO₃) (CO₃)·2H₂O or NaHCO₃·H₃BO₃·2H₂O). The thermal behaviors of thenardite/mirabilite and tincalconite/borax were evaluated at room temperature as a function of RH. Hydration of thenardite to mirabilite is very sluggish and does not begin until at least 85 % RH, whereas dehydration of mirabilite to thenardite occurs at ∼76 % RH. The reactions are accessible in the solid state and were not completely reversible on the time scale of these measurements. Qilianshanite appears stable under room conditions, as long as the RH is >20 %, supported by 2.5 months of observation during exposure to room air of known RH. Qilianshanite persists metastably for at least two days when exposed to both wet and 0% RH atmospheres at room temperature, observed during environment-controlled XRD. Below 20 % RH, qilianshanite sluggishly reacts to form tincalconite and nahcolite. When heated, qilianshanite broke down at 70 °C based on XRD results, and thermogravimetric analysis (TGA) confirmed a dehydration temperature of ∼75 °C. Tincalconite hydrated to borax at 80 % RH, and dehydration from borax to tincalconite occurred at 40–50 % RH, illustrating the effective reversibility of the reaction under room conditions. The minor phase nahcolite originally in qilianshanite remained in the residue of decomposed qilianshanite after heating to 125 °C, demonstrated by continuous XRD measurements, whereas nahcolite was largely dehydrated when heated to ∼100 °C during TGA. The difference can be attributed to the slower reaction kinetics in the environmental XRD. These results shed considerable light on the behavior of these minerals in the environment, particularly in evaporite deposits in Antarctica, where all of these minerals are reacting with the atmosphere on a diurnal-to-seasonal basis.

Original language	English
Article number	178759
Journal	Thermochimica Acta
Volume	693
DOIs	https://doi.org/10.1016/j.tca.2020.178759
State	Published - Nov 2020
Externally published	Yes

Funding

Natural sample (qilianshanite) collection was supported by an NSF grant to Prof. R. Harvey at Case Western Reserve University, and thanks go to R. Harvey, R. Socki, and E. Tonui for assistance with sample collection. Further mineralogical and thermodynamic analysis was supported by the Haydn Murray Applied Clay Mineralogy fund at Indiana University. The valuable comments and insights provided by the anonymous reviewer are greatly acknowledged. Partial support for TL to complete the manuscript was provided by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences, Geosciences Program under grant DESC0006878 to Ohio State University. Natural sample (qilianshanite) collection was supported by an NSF grant to Prof. R. Harvey at Case Western Reserve University , and thanks go to R. Harvey, R. Socki, and E. Tonui for assistance with sample collection. Further mineralogical and thermodynamic analysis was supported by the Haydn Murray Applied Clay Mineralogy fund at Indiana University . The valuable comments and insights provided by the anonymous reviewer are greatly acknowledged. Partial support for TL to complete the manuscript was provided by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences, Geosciences Program under grant DESC0006878 to Ohio State University.

Keywords

Mirabilite
Qilianshanite
TGA
Thenardite
XRD

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title = "Thermodynamics and dehydration/hydration behaviors of Na-sulfate, -borate, and -bicarbonate minerals",

abstract = "Detailed thermal experiments using relative humidity- (RH) and temperature-controlled X-ray diffraction (XRD) and H2O adsorption/desorption measurements were applied to understand the dehydration/hydration behaviors of thenardite/mirabilite (Na2SO4/Na2SO4·10H2O), tincalconite/borax (Na2B4O7·5H2O/Na2B4O7·10H2O), nahcolite (NaHCO3), and qilianshanite (NaH4 (BO3) (CO3)·2H2O or NaHCO3·H3BO3·2H2O). The thermal behaviors of thenardite/mirabilite and tincalconite/borax were evaluated at room temperature as a function of RH. Hydration of thenardite to mirabilite is very sluggish and does not begin until at least 85 % RH, whereas dehydration of mirabilite to thenardite occurs at ∼76 % RH. The reactions are accessible in the solid state and were not completely reversible on the time scale of these measurements. Qilianshanite appears stable under room conditions, as long as the RH is >20 %, supported by 2.5 months of observation during exposure to room air of known RH. Qilianshanite persists metastably for at least two days when exposed to both wet and 0% RH atmospheres at room temperature, observed during environment-controlled XRD. Below 20 % RH, qilianshanite sluggishly reacts to form tincalconite and nahcolite. When heated, qilianshanite broke down at 70 °C based on XRD results, and thermogravimetric analysis (TGA) confirmed a dehydration temperature of ∼75 °C. Tincalconite hydrated to borax at 80 % RH, and dehydration from borax to tincalconite occurred at 40–50 % RH, illustrating the effective reversibility of the reaction under room conditions. The minor phase nahcolite originally in qilianshanite remained in the residue of decomposed qilianshanite after heating to 125 °C, demonstrated by continuous XRD measurements, whereas nahcolite was largely dehydrated when heated to ∼100 °C during TGA. The difference can be attributed to the slower reaction kinetics in the environmental XRD. These results shed considerable light on the behavior of these minerals in the environment, particularly in evaporite deposits in Antarctica, where all of these minerals are reacting with the atmosphere on a diurnal-to-seasonal basis.",

keywords = "Mirabilite, Qilianshanite, TGA, Thenardite, XRD",

author = "Tingting Liu and Bish, {David L.}",

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year = "2020",

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doi = "10.1016/j.tca.2020.178759",

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AU - Liu, Tingting

AU - Bish, David L.

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N2 - Detailed thermal experiments using relative humidity- (RH) and temperature-controlled X-ray diffraction (XRD) and H2O adsorption/desorption measurements were applied to understand the dehydration/hydration behaviors of thenardite/mirabilite (Na2SO4/Na2SO4·10H2O), tincalconite/borax (Na2B4O7·5H2O/Na2B4O7·10H2O), nahcolite (NaHCO3), and qilianshanite (NaH4 (BO3) (CO3)·2H2O or NaHCO3·H3BO3·2H2O). The thermal behaviors of thenardite/mirabilite and tincalconite/borax were evaluated at room temperature as a function of RH. Hydration of thenardite to mirabilite is very sluggish and does not begin until at least 85 % RH, whereas dehydration of mirabilite to thenardite occurs at ∼76 % RH. The reactions are accessible in the solid state and were not completely reversible on the time scale of these measurements. Qilianshanite appears stable under room conditions, as long as the RH is >20 %, supported by 2.5 months of observation during exposure to room air of known RH. Qilianshanite persists metastably for at least two days when exposed to both wet and 0% RH atmospheres at room temperature, observed during environment-controlled XRD. Below 20 % RH, qilianshanite sluggishly reacts to form tincalconite and nahcolite. When heated, qilianshanite broke down at 70 °C based on XRD results, and thermogravimetric analysis (TGA) confirmed a dehydration temperature of ∼75 °C. Tincalconite hydrated to borax at 80 % RH, and dehydration from borax to tincalconite occurred at 40–50 % RH, illustrating the effective reversibility of the reaction under room conditions. The minor phase nahcolite originally in qilianshanite remained in the residue of decomposed qilianshanite after heating to 125 °C, demonstrated by continuous XRD measurements, whereas nahcolite was largely dehydrated when heated to ∼100 °C during TGA. The difference can be attributed to the slower reaction kinetics in the environmental XRD. These results shed considerable light on the behavior of these minerals in the environment, particularly in evaporite deposits in Antarctica, where all of these minerals are reacting with the atmosphere on a diurnal-to-seasonal basis.

AB - Detailed thermal experiments using relative humidity- (RH) and temperature-controlled X-ray diffraction (XRD) and H2O adsorption/desorption measurements were applied to understand the dehydration/hydration behaviors of thenardite/mirabilite (Na2SO4/Na2SO4·10H2O), tincalconite/borax (Na2B4O7·5H2O/Na2B4O7·10H2O), nahcolite (NaHCO3), and qilianshanite (NaH4 (BO3) (CO3)·2H2O or NaHCO3·H3BO3·2H2O). The thermal behaviors of thenardite/mirabilite and tincalconite/borax were evaluated at room temperature as a function of RH. Hydration of thenardite to mirabilite is very sluggish and does not begin until at least 85 % RH, whereas dehydration of mirabilite to thenardite occurs at ∼76 % RH. The reactions are accessible in the solid state and were not completely reversible on the time scale of these measurements. Qilianshanite appears stable under room conditions, as long as the RH is >20 %, supported by 2.5 months of observation during exposure to room air of known RH. Qilianshanite persists metastably for at least two days when exposed to both wet and 0% RH atmospheres at room temperature, observed during environment-controlled XRD. Below 20 % RH, qilianshanite sluggishly reacts to form tincalconite and nahcolite. When heated, qilianshanite broke down at 70 °C based on XRD results, and thermogravimetric analysis (TGA) confirmed a dehydration temperature of ∼75 °C. Tincalconite hydrated to borax at 80 % RH, and dehydration from borax to tincalconite occurred at 40–50 % RH, illustrating the effective reversibility of the reaction under room conditions. The minor phase nahcolite originally in qilianshanite remained in the residue of decomposed qilianshanite after heating to 125 °C, demonstrated by continuous XRD measurements, whereas nahcolite was largely dehydrated when heated to ∼100 °C during TGA. The difference can be attributed to the slower reaction kinetics in the environmental XRD. These results shed considerable light on the behavior of these minerals in the environment, particularly in evaporite deposits in Antarctica, where all of these minerals are reacting with the atmosphere on a diurnal-to-seasonal basis.

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KW - Qilianshanite

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M3 - Article

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JO - Thermochimica Acta

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ER -

Thermodynamics and dehydration/hydration behaviors of Na-sulfate, -borate, and -bicarbonate minerals

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