Solid–Liquid Phase Equilibria in Ternary Aqueous Systems (LiB5O8 + KB5O8 + H2O) and (LiB5O8 + NaB5O8 + H2O) at 288.15 K and 0.1 MPa

To achieve efficient separation of alkali metal borate resources from the brines of the salt lake to provide a theoretical basis, this paper adopts the isothermal dissolution equilibrium method to study the solid-liquid phase equilibrium and phase diagram of the ternary system (LiB5O8 + KB5O8 + H2O) and (LiB5O8 + NaB5O8 + H2O) at 288.15 K. The study grasps the changing law of solubility and physicochemical properties of the system, as well as analyses and identifies the solid phase in stable equilibrium. The results show that the stable phase diagrams of the two ternary systems at 288.15 K are of the simple eutectic type, containing one invariant point, two univariate saturated solubility curves, and two crystalline regions. Among them, the crystalline region of LiB5O8·5H2O is the smallest, indicating that it is not easy to precipitate from the saturated liquid phase, and the density and refractive index curves of each system show regular changes with the increase of LiB5O8 content.