Solubility Isotherm Determination of the H₃BO₃ + RbCl + H₂O and H₃BO₃ + NH₄Cl + H₂O Systems at T = 273.15, 298.15, 323.15, 348.15, and 363.15 K and Thermodynamic Modeling

Abstract

Highly concentrated boron is widespread in salt lake brine and nuclear wastewater. Treatment of these aqueous solutions involves the solubility of extensive boron-containing minerals. Recently, we concentrated on the temperature-dependent solubility of the H3BO3 + salt + water system. Here, we systematically determined the ternary solubility isotherms in the H3BO3 + RbCl + H2O and H3BO3 + NH4Cl + H2O systems at T = (273.15, 298.15, 323.15, 348.15 and 363.15) K, using an isothermal equilibrium method. The results showed that both ternary systems belonged to a simple eutectic case. The solubility isotherms consisted of the solubility branches of H3BO3(cr) and RbCl(cr) or NH4Cl(cr). Using a revised Pitzer–Simonson–Clegg (rPSC) model implemented in the ISLEC software, these ternary solubility data were represented by fitting the interaction parameters between H3BO3 and RbCl and H3BO3 and NH4Cl. With the help of these models, polythermal phase diagrams of the two ternary systems are predicted.

Solid–Liquid Equilibrium in the NH4Cl + RbCl + H2O and NH4Cl + CsCl + H2O Systems at 298.15 K

“…The PSC model parameters for the binary systems RbCl + H 2 O, CsCl + H 2 O and NH 4 Cl + H 2 O followed our previous work. , Mixing parameter W ( W NH4RbCl or W NH4CsCl ) is necessary for simulating the systems RbCl + NH 4 Cl + H 2 O and CsCl + NH 4 Cl + H 2 O. The parameters W NH4RbCl and W NH4CsCl were determined by fitting the experimental data as −1 and −2, respectively.…”

Solid–Liquid Equilibria (SLE) of the Quinary Reciprocal Aqueous System Li+, K+, Rb+//Cl–, Borate-H2O at 323.2 K

“…Accordingly, a series of phase equilibria studies have been done aimed at different types of brine. − As for the main components of the Pingluo brine, they can be simplified as the Li + , Na + , K + , Rb + , Mg 2+ //Cl – , Borate-H 2 O system. Therefore, to understand the thermodynamic behaviors of the complex system, phase diagrams of some subsystems have been measured. − For the borate-containing system, the crystalline form of boron appears in many polymeric forms such as BO 2 – , B­(OH) 4 – , B­(OH) 3 , B 4 O 7 2– , and B 5 O 8 – when the coexisting ions and temperature change. , As for the quinary system Li + , K + , Rb + //Cl – , Borate-H 2 O at 323.2 K, the corresponding nine ternary subsystems and five quaternary subsystems at 323.2 K have been studied. − The research results show that two boron species, B 4 O 7 2– and B 5 O 8 – , were found in the borate system containing potassium/lithium and rubidium; the solid solution [(K, Rb)­Cl] was formed in the chloride type system containing potassium and rubidium; and the rubidium carnallite RbCl·MgCl 2 ·6H 2 O was found in the chloride type system containing magnesium and rubidium. Commonly, the coexisting ions in the solution have a direct effect on the crystallization form of salts.…”