Solubility determination and thermodynamic modeling of solid−liquid equilibria in the LiBO2−Li2B4O7−H2O system at 298.15 K and 323.15 K

The solubilities and the refractive indices in the ternary system LiBO 2 −Li 2 B 4 O 7 −H 2 O at 298.15 K and 323.15 K were determined with the isothermal dissolution method. The phase diagrams and refractive index diagrams were drawn with the experimental values. The phase diagrams at 298.15 K and 323.15 K consist of one invariant point, two univariant curves and two crystallization regions corresponding to Li 2 B 4 O 7 ·3H 2 O, LiBO 2 ·8H 2 O (at 298.15 K) and LiBO 2 ·2H 2 O (at 323.15 K). Based on the Pitzer model, the mixing ion-interaction parameters ( θ B ( O H ) 4 − , B 4 O 5 ( OH ) 4 2 − and Ψ L i + , B ( O H ) 4 − , B 4 O 5 ( O H ) 4 2 − ) at 298.15 K and 323.15 K were fitted with the solubility data. A comparison shows that the calculated solubilities in the ternary system at 298.15 and 323.15 K agree well with the experimental data. The phase diagram and Pitzer model for the ternary system were then used to conduct isothermal evaporation simulation. Different salt will be obtained if the original solution point in different unsaturated regions.