Metastable Phase Equilibrium in the Aqueous Ternary System (KCl−CaCl₂−H₂O) at (288.15 and 308.15) K

Abstract

The solubility and the physicochemical properties (density and refractive index) in the liquid–solid metastable system (KCl−CaCl2−H2O) at (288.15 and 308.15) K were determined using the isothermal evaporation method. Based on the experimental data, the metastable phase diagrams and the diagrams of physicochemical properties vs composition in the system at (288.15 and 308.15) K were plotted. In the metastable phase diagrams of the ternary system at (288.15 and 308.15) K, there are in all one invariant point, two univariant curves, and two crystallization zones, corresponding to potassium chloride, antarcticite (CaCl2·6H2O) at 288.15 K, and potassium chloride, and calcium chloride tetrahydrate (CaCl2·4H2O), at 308.15 K. This system at both temperatures belongs to a simple eutectic type, and neither double salts nor solid solution were found. Based on the extended Harvie−Weare (HW) models and temperature-dependent equations at (288.15 and 308.15) K, respectively, the values of the Pitzer parameters β(0), β(1),and C φ for KCl and CaCl2, the mixed ion-interaction parameters θK,Ca and ΨK,Ca,Cl, the Debye–Hückel parameter A φ, and the standard chemical potentials of the minerals in the ternary system were obtained by fitting. Using the temperature-dependent equations and the standard chemical potentials of the minerals respectively, the predictive solubilities for the ternary system at both temperatures are presented. A comparison between the calculated and experimental results at each temperature shows that the predicted solubilities obtained with the extended HW model agree well with experimental data.

Stable (solid+liquid) phase equilibrium for the ternary systems (K2SO4+KH2PO4+H2O), (K2SO4+KCl+H2O) at T=313.15K

“…Maybe, it can be explained by different conditions, such as the precision of apparatus. Although the density value of KCl-H 2 O is 1.2364 g Á cm À3 at T = 308.15 K in reference [34], it is 1.2020 g Á cm À3 at T = 323.15 K in reference [24]. Except these literature data, we can see that our density value of KCl-H 2 O at T = 313.15 K keep consistent with the tendency comparing with other data.…”

“…But several data cannot keep consistent with the tendency, especially the density value of KCl-H 2 O at T = 308.15 K in Ref. [34] and refractive index data of K 2 SO 4 -H 2 O at T = 318.15 K in reference [33]. Maybe, it can be explained by different conditions, such as the precision of apparatus.…”

Solid–Liquid Metastable Equilibria for Solar Evaporation of Brines and Solubility Determination: A Critical Discussion

“…We do not want to burden the present paper with a complete list of references for 'metastable phase equilibria'. The typical experimental set-up used in most of the studies is, for example, found in references [1][2][3][4]. The authors call their experimental technique the 'isothermal evaporation method'.…”

“…The relative humidity of the air is usually quite low (typically, 20-35% RH) resulting in evaporation from the salt solution. The authors attempt to mimic the evaporation rates of particular salt lakes by adjusting both the flow velocity and the relative humidity in the chamber [1][2][3][4]. Solutions are not mixed during evaporation either by agitation or by stirring.…”

Simulation studies on metastable phase equilibria in the aqueous ternary systems (NaCl-MgCl2-H2O) and (KCl-MgCl2-H2O) at 308.15 K

“…Although metastable equilibria of several systems have been reported, such as the sea water system (Na-K-Mg-Cl-SO 4 [6][7][8][9], those of the titled systems (NaCl-MgCl 2 -H 2 O) and (KCl-MgCl 2 -H 2 O) at 308.15 K have not been reported in the literature in terms of describing their metastable behavior. According to statistical meteorologic analyses in the most recent 20 years, the climate conditions in salt lake regions of the Qaidam Basin are generally windy, arid, with little rainfall and a great evaporating capacity.…”