Phase diagrams and thermochemical modeling of salt lake brine systems. II. NaCl+H2O, KCl+H2O, MgCl2+H2O and CaCl2+H2O systems

Li, Dongdong; Zeng, Dewen; Yin, Xiang; Han, Haijun; Guo, Lijiang; Yao, Yan

doi:10.1016/j.calphad.2016.03.007

Cited by 82 publications

(54 citation statements)

References 124 publications

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“…The three phases meet at the eutectic point of NaCl 30 located at a concentration of 3.99 M (23.3% m/m) and a temperature of 251.9 K. Upon further cooling, the salt solution crystallizes and consists of a mixture of NaCl×2H2O hydrates and ice crystals. The phase diagram of NaCl and that of other salt solutions has been investigated previously, and it is important for modeling sea and lake water 31 , understanding the marine cloud microphysics 32 and improving cryobiological applications 33 .…”

Section: Introductionmentioning

confidence: 99%

Brine rejection and hydrate formation upon freezing of NaCl aqueous solutions

Tsironi

Schlesinger

Späh

et al. 2020

Phys. Chem. Chem. Phys.

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Studying the freezing of saltwater on a molecular level is of fundamental importance for improving freeze desalination techniques. Here, we investigate the freezing process of NaCl solutions using a combination of x-ray diffraction and molecular dynamics simulations (MD) for different salt-water concentrations, ranging from seawater conditions to saturation. A linear superposition model reproduces well the brine rejection due to hexagonal ice Ih formation and allows us to quantify the fraction of ice and brine. Furthermore, upon cooling at T = 233 K we observe the formation of NaCl×2H2O hydrates (hydrohalites), which coexist with ice Ih. MD simulations are utilized to model the formation of NaCl crystallites. From the simulations we estimate that the salinity of the newly produced ice is 0.5% mass percent (m/m) due to ion inclusions, which is within the salinity limits of fresh water. In addition, we show the effect of ions on the local ice structure using the tetrahedrality parameter and follow the crystalite formation by using the ion coordination parameter and cluster analysis. Fig.1 A schematic phase diagram of NaCl aqueous solution.Above the melting point and in low concentration of NaCl the solution is in liquid phase. At higher concentrations, saturation leads to NaCl crystal or NaCl×2H2O hydrates formation (shown on the right). Upon decreasing the temperature below the melting point, ice is formed pushing out the salt, in a process called brine rejection. When decreasing further the temperature below 251.9 K, ice and NaCl×2H2O crystals coexist. These authors contributed equally to this work.

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Section: Introductionmentioning

confidence: 99%

Brine rejection and hydrate formation upon freezing of NaCl aqueous solutions

Tsironi

Schlesinger

Späh

et al. 2020

Phys. Chem. Chem. Phys.

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“…It can be concluded that MgCl 2 ·8H 2 O is the only hydrate form of magnesium chloride at 258 K. There is one hydrated salt of sodium chloride, that is, NaCl·2H 2 O. The previous studies ,− have found that, when at 258 K, the NaCl crystallization form is NaCl·2H 2 O in binary or mixed ternary systems.…”

Section: Resultsmentioning

confidence: 91%

Phase Equilibria in the Aqueous Quinary System Na⁺, Mg²⁺//Cl^–, NO₃^–, SO₄^2––H₂O and Its Subsystem at 258 K

et al. 2019

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The experimental study on phase equilibria at 258 K in the quinary system Na+, Mg2+//Cl–, NO3 –, SO4 2––H2O and its subsystem Na+, Mg2+//Cl–, NO3 ––H2O were investigated using the isothermal solution equilibrium method. The phase diagrams were obtained on the basis of the measured data. The investigated systems belong to simple cosaturated types without double salts formed. The quinary system saturated with NaCl·2H2O contains three isothermal-invariant points, seven univariant curves, and five crystallization fields corresponding to Na2SO4·10H2O, NaNO3, MgCl2·8H2O, MgSO4·7H2O, and Mg(NO3)2·6H2O. With a view to the crystallization zones, the crystallization area of salt Na2SO4·10H2O occupies the largest part, meaning it can be more easily separated from the solution as compared to the other coexisting salts in this system. Comparison with the similar diagram type at 298 K shows that all fields, in general, have decreased except Na2SO4·10H2O; the main difference is that the crystallization fields of double salts disappear. These fundamental data could be valuable for promoting the research and application of crystallization processes at low temperature and further theoretical exploration.

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“…The phase equilibrium of the CaCl 2 –H 2 O system was studied by Li and Zeng in a wide temperature range from 224.58 to 462.05 K, and various hydrate salts of calcium chloride CaCl 2 · n H 2 O ( n = 1/3, 1, 2, 4, 6) were formed . The transition temperatures of different hydrate forms of CaCl 2 are as below When the research temperature is in the range from 224.58 to 303.35 K, the crystalline form of calcium chloride is CaCl 2 ·6H 2 O.…”

Section: Resultsmentioning

confidence: 99%

“…The Janecke index of J B can be defined as follows (1) (2) The phase equilibrium of the CaCl 2 −H 2 O system was studied by Li and Zeng in a wide temperature range from 224.58 to 462.05 K, and various hydrate salts of calcium chloride CaCl 2 •nH 2 O (n = 1/3, 1, 2, 4, 6) were formed. 21 The transition temperatures of different hydrate forms of CaCl 2 are as below…”

Section: Resultsmentioning

confidence: 99%

Measurement and Correlation of Phase Equilibria of Ammonium, Calcium, Aluminum, and Chloride in Aqueous Solution at 298.15 K

Yu¹,

Liu²,

Zheng³

et al. 2019

J. Chem. Eng. Data

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The equilibrium data on the aqueous quaternary system NH 4 Cl−CaCl 2 −AlCl 3 −H 2 O at 298.15 K were investigated by using the isothermal dissolution method, and the corresponding diagrams were constructed. There are three fields of crystalline in the phase diagram, which correspond to three single salts, aluminum chloride hexahydrate (AlCl 3 •6H 2 O), ammonium chloride (NH 4 Cl), and calcium chloride hexahydrate (CaCl 2 •6H 2 O). The main crystallization field is salt NH 4 Cl. The water content reaches the minimum value at the quaternary invariant point F, while the refractive index goes to the maximum value at point F. The equilibrium thermodynamics data of the calculation of the aqueous quaternary system NH 4 Cl− CaCl 2 −AlCl 3 −H 2 O at 298.15 K were done by using the Pitzer and extended Pitzer−Harvie−Weare thermodynamic model. It can be seen that the calculation values agree well with the experimental data.

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Phase diagrams and thermochemical modeling of salt lake brine systems. II. NaCl+H2O, KCl+H2O, MgCl2+H2O and CaCl2+H2O systems

Cited by 82 publications

References 124 publications

Brine rejection and hydrate formation upon freezing of NaCl aqueous solutions

Brine rejection and hydrate formation upon freezing of NaCl aqueous solutions

Phase Equilibria in the Aqueous Quinary System Na⁺, Mg²⁺//Cl^–, NO₃^–, SO₄^2––H₂O and Its Subsystem at 258 K

Measurement and Correlation of Phase Equilibria of Ammonium, Calcium, Aluminum, and Chloride in Aqueous Solution at 298.15 K

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Phase diagrams and thermochemical modeling of salt lake brine systems. II. NaCl+H2O, KCl+H2O, MgCl2+H2O and CaCl2+H2O systems

Cited by 82 publications

References 124 publications

Brine rejection and hydrate formation upon freezing of NaCl aqueous solutions

Brine rejection and hydrate formation upon freezing of NaCl aqueous solutions

Phase Equilibria in the Aqueous Quinary System Na+, Mg2+//Cl–, NO3–, SO42––H2O and Its Subsystem at 258 K

Measurement and Correlation of Phase Equilibria of Ammonium, Calcium, Aluminum, and Chloride in Aqueous Solution at 298.15 K

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Phase Equilibria in the Aqueous Quinary System Na⁺, Mg²⁺//Cl^–, NO₃^–, SO₄^2––H₂O and Its Subsystem at 258 K