Stable phase equilibrium of the quaternary system NaCl-MgCl2-NH4Cl-H2O at 348.15 K and its application in industry

In this work, the phase equilibrium solubility data of a quaternary system NaCl–NH4Cl–MgCl2–H2O and its two ternary subsystems (NaCl–NH4Cl–H2O and NaCl–MgCl2–H2O) were measured by an isothermal solubility equilibrium method and a wet slag method. For the two ternary subsystems (NaCl–NH4Cl–H2O and NaCl–MgCl2–H2O), the solubility of the equilibrium liquid phase and physical properties (density and viscosity) are determined: this system is simple, contains a cosaturated point and three crystalline regions, and the solubility experiment data is compared with the literature values, fitting the invariant point under different temperatures. It can provide basic data for a brine system containing ammonium chloride, sodium chloride, magnesium chloride, and so on. The solubility of the quaternary system NaCl–MgCl2–NH4Cl–H2O was measured by an isothermal method, and the corresponding phase diagrams were drawn. From the phase diagrams, it is found that there are two cosaturated points and four solid-phase crystalline zones; the solid-phase crystallization region corresponds to NaCl, MgCl2·6H2O, NH4Cl, and MgCl2·NH4Cl·6H2O, respectively. The system can guide the dehydration and deamination of ammonium carnallite to produce anhydrous magnesium chloride.

Section: Results and Discussionmentioning

confidence: 99%

Solid–Liquid Phase Equilibria of NaCl–NH₄Cl–MgCl₂–H₂O and Its Subsystems NaCl–NH₄Cl–H₂O and NaCl–MgCl₂–H₂O at T = 303.15 K

Ding

Zhang

et al. 2021

“…Unfortunately, similar articles from the same group have been published in this and other journals following the same pattern: short equilibration times (a few hours) in test tubes, claiming to have determined stable equilibria even in cases of solid-solution formation, Pitzer model not correctly reported, and technological applications therefore questionable. − …”

Section: Discussionmentioning

confidence: 99%

Comment on “Study on Phase Equilibrium of the K⁺, Mg²⁺//Cl^–, SO₄^2– + H₂O Quaternary System at 353.15 K and Its Application”

Voigt

Königsberger

2020

The experimental investigation of phase equilibria in this system at elevated temperatures is essential for improving the thermodynamic models describing the aqueous geochemistry of oceanic salts as well as for industrial processing of oceanic salt deposits. 2 However, an inspection of the article by Kang et al. 1 revealed that the experimental data, the thermodynamic model, and the presentation of the results do not meet scientific standards. In the following sections, we will comment on these three aspects (Table numbers refer to the paper of Kang et al.).

“…Until now, there have been some experimental and theoretical studies which relate to the hexacomponent system NH 4 Cl–MgCl 2 –CaCl 2 –SrCl 2 –AlCl 3 –H 2 O, as described below: binary systems of SrCl 2 –H 2 O at 252.2–524.2 K, CaCl 2 –H 2 O at 239.2–523.2 K, and MgCl 2 –H 2 O at 223.2–503.2 K; ternary systems of MgCl 2 –CaCl 2 –H 2 O at 273.2–368.2 K, − CaCl 2 –SrCl 2 –H 2 O at 288.2–387.2 K, − MgCl 2 –SrCl 2 –H 2 O at 288.2–373.2 K, − NH 4 Cl–CaCl 2 –H 2 O at 273.2–348.2 K, − AlCl 3 –CaCl 2 –H 2 O at 278.2–363.2 K, , NH 4 Cl–MgCl 2 –H 2 O at 273.2–308.2 K, − AlCl 3 –SrCl 2 –H 2 O, NH 4 Cl–AlCl 3 –H 2 O, MgCl 2 –AlCl 3 –H 2 O at 298.2 K; quaternary systems of NH 4 Cl–CaCl 2 –AlCl 3 –H 2 O at 283.2–353.2 K, , MgCl 2 –SrCl 2 –AlCl 3 –H 2 O at 298.2 K, and NH 4 Cl–MgCl 2 –SrCl 2 –H 2 O at 298.2 K . The results show that (1) the solid solutions [(Ca, Sr)Cl 2 ]·6H 2 O and [(Sr, Ca)Cl 2 ]·6H 2 O are formed in the chloride-type system with the coexistence of strontium and calcium; (2) when magnesium chloride coexists with calcium or ammonium, it is easy to form double salts 2MgCl 2 ·CaCl 2 ·12H 2 O and NH 4 Cl·MgCl 2 ·6H 2 O; (3) strontium chloride can form into various hydrated salts at different temperatures, such as SrCl 2 ·6H 2 O, SrCl 2 ·2H 2 O, and SrCl 2 ·H 2 O; (4) the crystallization form of strontium chloride is also related to the coexisting ions, when MgCl 2 salt coexists with SrCl 2 ·6H 2 O at 298.2 K, both SrCl 2 ·6H 2 O and SrCl 2 ·2H 2 O exist in the systems of MgCl 2 –SrCl 2 –H 2 O and SrCl 2 –NH 4 Cl–MgCl 2 –H 2 O at 298.2 K. As for the quaternary systems NH 4 Cl–SrCl 2 –AlCl 3 –H 2 O and NH 4 Cl–MgCl 2 –AlCl 3 –H 2 O, they are the basic subsystems of the hexacomponent system NH 4 Cl–MgCl 2 –CaCl 2 –SrCl 2 –AlCl 3 –H 2 O, and the ternary subsystems NH 4 Cl–SrCl 2 –H 2 O, NH 4 Cl–MgCl 2 –H 2 O, AlCl 3 –SrCl 2 –H 2 O, NH 4 Cl–AlCl 3 –H 2 O, and MgCl 2 –AlCl 3 –H 2 O of these two quaternary systems at 298.2 K have been done by our previous works, while there is scarcely any literature about the phase equilibria of these two quaternary systems.…”

Section: Introductionmentioning

confidence: 99%

Phase Equilibria of Quaternary Systems Containing the Chlorides of Ammonium, Strontium(Magnesium), and Aluminum at 298.2 K

Ren

Zheng

et al. 2022

The phase equilibria of the quaternary systems NH 4 Cl−SrCl 2 −AlCl 3 −H 2 O and NH 4 Cl−MgCl 2 −AlCl 3 −H 2 O at 298.2 K were investigated by using the isothermal dissolution method. The solubility, density, and refractive index of the systems were measured experimentally, and the related phase diagrams, density/refractive index versus composition diagrams, are plotted. There is one quaternary invariant point and three crystallization regions corresponding to single salts NH 4 Cl, AlCl 3 •6H 2 O, and SrCl 2 •6H 2 O in the phase diagram of the system NH 4 Cl−SrCl 2 −AlCl 3 −H 2 O at 298.2 K, which belongs to a simple system. In addition to the single salts NH 4 Cl, AlCl 3 •6H 2 O, and MgCl 2 •6H 2 O, the double salt NH 4 Cl•MgCl 2 •6H 2 O is formed in the quaternary system NH 4 Cl−MgCl 2 −AlCl 3 −H 2 O at 298.2 K, which indicates that the addition of magnesium makes the interaction relationship between Al 3+ , NH 4+ , and Mg 2+ more complex and increases the difficulty of separation of magnesium. The crystallization region of NH 4 Cl is the largest in both the systems, which indicates that NH 4 Cl is much easier to separate than the other salts from the two systems.