Thermodynamic properties and thermodynamic modelling for aqueous mixed system containing lithium metaborate and sodium metaborate

The pH values, solubilities and water activities in the system LiB(OH) 4 –NaB(OH) 4 –H 2 O at 323.15 K were investigated. The mole fractions of boron species were calculated in the aqueous borate solutions, and the distribution and relevant mechanism were also discussed. The solubility diagrams in the ternary system were drawn at 323.15 K. The phase diagram consists of two single salt regions for LiB(OH) 4 and NaB(OH) 4 ·2H 2 O, one invariant point co-saturated with the above salts. On the basis of the Pitzer model, the Pitzer binary parameters and mixing parameters were fitted with the water activities, saturated vapour pressure and solubilities in the ternary system. The dissolution equilibrium constants ( K sp) of LiB(OH) 4 and NaB(OH) 4 ·2H 2 O were calculated using the experimental solubility data. The calculated solubilities with the parameters and K sp agree well with the experimental data.