Studies on stable phase equilibria of quaternary system LiBr-NaBr-SrBr2-H2O at 308.15 and 323.15 K

Abstract

The stable phase equilibria of LiBr–NaBr–SrBr2–H2O were studied at 323.15 K and 308.15 K by the isothermal solution equilibrium method. The isothermal phase diagram of the quaternary system was drawn by using solubilities of salts and solid phase identification. The X-ray powder diffraction method was used to identify the corresponding equilibrium solid phases of the invariant points in the quaternary system. The quaternary system LiBr–NaBr–SrBr2–H2O at 323.15 K has no double salts or solid solution. There are two invariant points, five univariant curves, and four crystallization fields corresponding to LiBr•H2O, NaBr, SrBr2•2H2O, and SrBr2•6H2O respectively, of which NaBr has the largest crystallization field, indicating that its solubility is the smallest and it is the easiest to be precipitated from the saturated solution. The phase diagram of quaternary system LiBr-NaBr-SrBr2-H2O at 308.15 K has three invariant points, seven univariant curves, and five crystallization fields corresponding to LiBr•2H2O, NaBr, NaBr•2H2O, SrBr2•2H2O, and SrBr2•6H2O, respectively. Among them, the crystallization field of LiBr•2H2O is the smallest, indicating that the solubility of LiBr•2H2O in this system is the largest.