Phase equilibria in the aqueous ternary systems (LiCl + LiBO2 + H2O) and (Li2SO4 + LiBO2 + H2O) at 323.15 K and 0.1 MPa

• Solubilities of two aqueous systems of lithium salts were determined using isothermal dissolution equilibrium and wet-residue solid phase methods.
• Density, refractive index and pH of those systems at 323.15 K were also reported.
• Component of Li2SO4 in the aqueous solution has a strong salting-out effect to LiBO2.
• Calculated and experimental values of refractive indices in both systems agree well.

Combining the methods of isothermal dissolution equilibrium and the wet-residue solid phase (Schreinemarkers rule), the phase equilibria of the ternary systems (LiCl + LiBO2 + H2O) and (Li2SO4+ LiBO2 + H2O) at 323.15 K and 0.1 MPa were investigated. On the basis of the experimental data on solubilities and the physicochemical properties including density, refractive index and pH value, the phase diagrams and physicochemical properties versus composition diagrams of the two systems were plotted. For the two systems, there are both in one invariant point, two univariant curves, and two crystallization regions corresponding to lithium metaborate dehydrate (LiBO2·2H2O, Lb2), lithium chloride monohydrate (LiCl·H2O i.e. Lc1, in the former) and lithium sulfate monohydrate (Li2SO4·H2O i.e. Ls1, in the later), and the area of the crystallization region of Lb2 is the largest when compared with those of Lc1 and Ls1, and those results demonstrate that the solubility of lithium metaborate is the lowest. A comparison of the phase diagrams between this work at 323.15 K and the literature at (288.15, 298.15 and 308.15) K in the former system, the crystallization region of LiBO2·8H2O existed at 288.15, 298.15 and 308.15 K is disappeared at 323.15 K. Relationships between solubility and temperature for LiBO2 and LiCl are both in positive correlation obviously. However, a comparison of the phase diagrams between this work at 323.15 K and the literature at (288.15, 298.15) K in the later system, it was found that the mineral LiBO2·8H2O existed at 288.15 and 298.15 K is replaced by LiBO2·2H2O, and the component of Li2SO4 in the solution has a relatively strong salting-out effect to LiBO2, and the concentrations of LiBO2 in the solution are decreased considerably with the increasing of lithium sulfate concentration in the solution. The calculated values of refractive index using empirical equations for the two ternary systems are in good agreement with the experimental values.

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