Solid-Liquid Equilibria of Ternary Systems LiBr + NaBr + Methanol, LiBr + KBr + Methanol, and NaBr + KBr + Methanol at 288.2 K and Molecular Modeling Predicted by EOS-Based DFT

Solid–liquid phase equilibria of the ternary systems LiBr + NaBr + methanol, LiBr + KBr + methanol, and NaBr + KBr + methanol at 288.2 K were investigated by the isothermal dissolution equilibrium method. The phase diagrams and density–composition diagrams of ternary systems are drawn. The results demonstrate that phase diagrams of the three ternary systems at 288.2 K are composed of one invariant point, two univariate solubility curves, and two crystallization fields. The density at the invariant point is greater than the experimental data at other liquidus points. Additionally, a molecular model of phase equilibria in methanol solvents was creatively established. This has been accomplished by the incorporation of density functional theory (DFT) into the development of equations of state (EOS). By comparing the experimental data of three ternary systems with the calculated results of the model, it is found that the DFT model can describe the solid–liquid equilibria of these organic solvent electrolytes well and has high accuracy and reliability. The investigation on the phase equilibria of three ternary systems can provide data basis for the comprehensive development and separation of lithium, sodium, potassium, and bromine resources in organic solvents.