Solid–Liquid Equilibrium of Quinary Aqueous Solution Composed of Lithium, Potassium, Rubidium, Magnesium, and Borate at 323.15 K

Abstract

To understand the thermodynamic behaviors of the borate-containing system, the solid−liquid equilibrium data (solubilities, density, and refractive index) of quinary aqueous solution composed of lithium, potassium, rubidium, magnesium, and borate at 323.15 K were determined by using the isothermal dissolution method. The crystalloid forms of the solid phase were confirmed by the X-ray diffraction method. Results show that four single salts Li 2 B 4 O 7 •3H 2 O, K 2 B 4 O 7 •4H 2 O, RbB 5 O 8 • 4H 2 O, and MgB 4 O 7 •9H 2 O were formed at 323.15 K in the quinary invariant point, with no double salt or solid solution found. Under the condition of Li 2 B 4 O 7 saturation, the crystallization region of MgB 4 O 7 •9H 2 O occupied the largest crystallization region, and the salt K 2 B 4 O 7 •4H 2 O had the smallest region. Among the four salts, the crystalline regions of the salts MgB 4 O 7 • 9H 2 O and RbB 5 O 8 •4H 2 O changed obviously at 323.15 and 348.15 K, that of MgB 4 O 7 •9H 2 O enlarged at 323.15 K, and those of RbB 5 O 8 •4H 2 O and K 2 B 4 O 7 •4H 2 O decreased.

Phase Equilibria on the Reciprocal Quaternary System K+, Rb+ // Cl–, and Borate–H2O at T = 323.2 K and p = 94.77 kPa

“…The sevencomponent system Li + , Na + , K + , Rb + , Mg 2+ // Cl − , and borate−H 2 O can be used to describe the composition in the Pingluo underground brine. Until now, some phase equilibria of subsystems related to the above mentioned complex system have been done: ternary systems, such as Li + // Cl − , BO 20,21 The results show that the crystalline form of boron is related to the coexisting ions and temperature. Boron appears in many polymeric forms such as BO − in the solution containing borate.…”

“…The seven-component system Li + , Na + , K + , Rb + , Mg 2+ // Cl – , and borate–H 2 O can be used to describe the composition in the Pingluo underground brine. Until now, some phase equilibria of subsystems related to the above mentioned complex system have been done: ternary systems, such as Li + // Cl – , BO 2 – –H 2 O at 288.2–323.2 K, , Li + , K + // borate–H 2 O and Li + , Rb + // borate–H 2 O at 323.2 K, K + , Rb + // borate–H 2 O and Rb + , Mg 2+ // borate–H 2 O at 323.2 K, Mg 2+ // Cl – , B 6 O 10 2– –H 2 O at 288.2 and 308.2 K, , and Mg 2+ // Cl – , B 4 O 7 2– –H 2 O at 273.2 K; quaternary systems, such as Li + , Na + , Mg 2+ // B 4 O 7 2– –H 2 O at 273.2 K, Li + , K + , Mg 2+ // borate–H 2 O at 348.2 K, Li + , Rb + , Mg 2+ // borate–H 2 O at 298.2–348.2 K, − Na + , Mg 2+ // Cl – , B 4 O 7 2– –H 2 O at 273.2 K, Rb + , Mg 2+ // Cl – , borate–H 2 O at 323.2 and 348.2 K; , and quinary system such as Li + , K + , Rb + , Mg 2+ // borate–H 2 O at 323.2 and 348.2 K. , The results show that the crystalline form of boron is related to the coexisting ions and temperature. Boron appears in many polymeric forms such as BO 2 – , B­(OH) 4 – , B 3 O 3 (OH) 4 – , B 4 O 5 (OH) 4 2– , and B 5 O 6 (OH) 4 – in the solution containing borate. − …”

Stable Phase Diagram of the Quaternary Water–Salt System Li+, Na+, Rb+//SO42–·H2O at 298.2 and 323.2 K (P = 94.5 kPa)

“…The research results can be used to explore the chemical production process and guide the formulation of the comprehensive utilization process of salt lake brine resources. 13 Up to now, a lot of work have been carried out on phase equilibrium for different types of salt lakes, for example, K + , Rb + // Cl − − H 2 O at 298.15 K; 14 Na + , Mg 2+ , NH 4 + // Cl − − H 2 O at 348.15 K; 15 Na + , Rb + // Cl − − H 2 O at 288.15, 298.2, and 308.15 K; 16 Na + , Rb + , Mg 2+ //Cl − − H 2 O at 298.2 K; 17 Li + , Rb + , Mg 2+ //borate − H 2 O at T = 323 K; 18 Rb + (Mg 2+ )//Cl − , and borate − H 2 O at 323 K; 19 and Li + , K + , Rb + , Mg 2+ // borate − H 2 O, 20 K + , Rb + , Cs + //SO 4 2− − H 2 O at 298.2 K 21 have been used to comprehensively utilize the salt lake. According to the reported sulfate-containing literature, for the quaternary systems Li + , Na + , Cs + //SO 4 2− − H 2 O at 298.2 K; 22 Li + , Na + , Mg 2+ // SO 4 2− − H 2 O at 323 K, 23 and Li + , Cs + , Mg 2+ // SO 4 2− − H 2 O at 298.2 K, 24 it was found that lithium sulfate is difficult to be extracted directly from brine in its single salt form by isothermal crystallization.…”

Polyacrylonitrile/Crown Ether Composite Nanofibres With High Efficiency for Adsorbing Li(I): Experiments and Theoretical Calculations

“…Given the rapid development of portable electronic products and new-energy vehicles, the price of, and demand for, lithium resources have increased sharply in recent years (Xu et al, 2020). According to a United States Geological Survey (USGS) report, 62% of lithium resources in the world are present in brine in salt lakes (Yu et al, 2019). Therefore, it is of economic and strategic significance to extract lithium resources from the brine in salt lakes.…”