Dehydration Pathways of Gypsum and the Rehydration Mechanism of Soluble Anhydrite γ-CaSO 4

The dehydration products of gypsum under different temperature and water vapor pressure were investigated by thermodynamic theory. Additionally, the rehydration mechanism of soluble anhydrite was also studied by Monte Carlo (MC) simulations. The thermodynamic calculation results reveal that the dehy...

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Veröffentlicht in:ACS omega 2019-04, Vol.4 (4), p.7636-7642
Hauptverfasser: Tang, Yongbo, Gao, Jianming, Liu, Chuanbei, Chen, Xuemei, Zhao, Yasong
Format: Artikel
Sprache:eng
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Zusammenfassung:The dehydration products of gypsum under different temperature and water vapor pressure were investigated by thermodynamic theory. Additionally, the rehydration mechanism of soluble anhydrite was also studied by Monte Carlo (MC) simulations. The thermodynamic calculation results reveal that the dehydration mechanism of gypsum significantly depended on ambient temperature and water vapor pressure. In the high-temperature and low water vapor pressure region, gypsum dehydrates to form γ-CaSO in a single-step process (CaSO ·2H O → γ-CaSO ); with increasing water vapor pressure, gypsum undergoes the CaSO ·2H O → γ-CaSO → β-CaSO ·0.5H O reaction path and as water vapor pressure increases further, the occurrence of a two-step conversion path CaSO ·2H O → β-CaSO ·0.5H O → γ-CaSO was observed. It was also found that gypsum is stable in the low-temperature and high water vapor pressure region and does not dehydrate to form any calcium sulfate hemihydrate. Finally, the rehydration mechanism of soluble anhydrite was studied by MC simulations. The simulation results are in agreement with the experimental data and support the finding that γ-CaSO rehydration forms CaSO ·0.67H O in high relative humidity. Another important result revealed by the MC simulation is that γ-CaSO has an extraordinary ability to capture water molecules from an extremely dry atmosphere, which is very useful in some fields, such as in drying processes and even for extracting liquid water from extremely dry atmosphere.
ISSN:2470-1343
2470-1343
DOI:10.1021/acsomega.8b03476