Study on the Metastable Equilibria of the Salt Lake Brine System Li₂SO₄ + Na₂SO₄ + K₂SO₄ + Li₂B₄O₇ + Na₂B₄O₇ + K₂B₄O₇ + H₂O at 288 K

Abstract

An experimental study on phase equilibria at 288 K in the quinary system Li + + Na + + K + + SO 4 2-+ B 4 O 7 2-+ H 2 O was performed using the isothermal evaporation method. Equilibrium solubility and density of the solution were measured. The equilibrium phase diagram for the solution saturated with the salt Li 2 B 2 O 4 ‚16H 2 O was constructed. The phase diagram of this system consists of 7 invariant points, 14 univariant curves, and 8 crystallization fields corresponding to potassium tetraborate pentahydrate (K 2 B 4 O 7 ‚5H 2 O), borax (Na 2 B 4 O 7 ‚10H 2 O), potassium sulfate, lithium sulfate monohydrate (Li 2 SO 4 ‚H 2 O), sodium sulfate, lithium-potassium sulfate double salt (Li 2 SO 4 ‚K 2 SO 4 ), lithium-sodium sulfate double salt (Li 2 SO 4 ‚Na 2 SO 4 ), and potassium-sodium sulfate double salt (3K 2 SO 4 ‚Na 2 SO 4 ). There are three kinds of double salts formed in the system. The crystallization forms of lithium and potassium borate were K 2 B 4 O 7 ‚5H 2 O and Li 2 B 2 O 4 ‚16H 2 O, respectively, which are different from the usual forms of K 2 B 4 O 7 ‚4H 2 O and Li 2 B 4 O 7 ‚3H 2 O that occur at stable equilibrium.

Metastable Phase Diagram of the Quaternary System Li+, Na+//Cl–, B4O72––H2O at 273 K

“…Besides the experimental temperature, metastable or stable conditions may also influence the crystalloid form of lithium borate. Compared the metastable and stable phase diagrams of the quinary system Li + , Na + , K + //SO 4 2– , B 4 O 7 2 –H 2 O at the same temperature 288 K, the results show that the crystalloid form of lithium borate is LiBO 2 ·8H 2 O in the metastable condition, whereas that is Li 2 B 4 O 7 ·3H 2 O in the stable condition . Therefore, the equilibrium solid phase of lithium borate in the given system can be affected by temperature and metastable or stable condition.…”

The Solubilities and Physicochemical Properties of the Aqueous Quaternary System Li+, K+, Rb+//Borate–H2O at 348 K

“…Furthermore, some salt–water systems focused on borate containing systems have been done by our research group, such as ternary systems Li + , K + //borate–H 2 O, Rb + , Mg 2+ //borate–H 2 O and Rb + , Cl – //borate–H 2 O at 348 K; quaternary systems Li + //Cl – , SO 4 2– , borate–H 2 O at 273 K and Li + , Na + , K + //borate–H 2 O at 288 K; quinary systems Li + , Na + , K + //SO 4 2– , borate–H 2 O at 288 K and Li + //Cl – , CO 3 2– , SO 4 2– , borate–H 2 O at 298 K. Results show that: the crystalloid form of rubidium borate is RbB 5 O 8 ·4H 2 O at 348 K; the equilibrium solid phases of lithium borate correspond to LiBO 2 ·8H 2 O at 273 K, 288 K , and Li 2 B 4 O 7 ·3H 2 O at 298 K, 348 K; , the crystalloid form of potassium borate is K 2 B 4 O 7 ·4H 2 O at 288 K and 348 K. ,, …”

“…It is well-known that the solubility data of inorganic salts along with the phase diagram provide a very important basis for the comprehensive utilization of brine. In the solution with borate, the solubility behavior is complex because boron appears in many forms such as B 16 348 K; 10,11 the crystalloid form of potassium borate is K 2 B 4 O 7 •4H 2 O at 288 K and 348 K. 10,14,15 To date, the stable phase equilibrium of the quaternary system containing the borates of lithium, rubidium, and potassium in aqueous solution at 348 K has not been reported. Consequently, the solubilities and physicochemical properties (densities, refractive indices, and pH values) of the quaternary system are presented here in detail.…”

Salt-Forming Regions of Na+, Mg2+//Cl–, SO42––H2O System at 373.15 K in the Nonequilibrium State of Isothermal Boiling Evaporation

“…2 Moreover, metastable phenomena occur in the complex systems, so that its salt precipitation sequence does not always follow the solubility diagrams. Thereby, the metastable phase diagram determined by the isothermal evaporation method is also used to present the phase regions within natural evaporation processes, such as the so-called "solar phase diagram" of the Na + , K + , Mg 2+ //Cl − , SO 4 2− −H 2 O system at 298 K (partial) by Kurnakov and Nikolaev 3 and at (288, 298, and 305) K by Jin et al 4−6 In recent years, more data about the metastable equilibria of sulfate, carbonate, and borate and Li + , Mg 2+ , and Rd + containing systems at ambient temperature are published by Sang et al, 7,8 Zeng et al, 9,10 Deng et al 11−13 The reasoning of metastable phenomena was also studied through crystallization kinetics with an isothermal decrease of the supersaturation method 14 or on the micromechanism of solution with Raman spectroscopy 15 by Tepavitcharova et al The solution structure was also studied with an X-ray diffraction method by Fang et al 16 Salt-Forming Behavior in Nonequilibrium State. Evaporation processes such as multieffect evaporation are usually operated at the nonequilibrium stable state or dynamic state with a high evaporation intensity at a boiling temperature from (323 to 393) K. The undesirable metastable phenomena exist but actually play a valuable role in industrial processes.…”