Thermodynamic modeling of boron species in brine systems containing metaborate and its application in evaporation simulation

Abstract

The solubilities in the system NaCl–Na2SO4–NaB(OH)4–H2O and its subsystems were calculated with two models based on Pitzer model. The model I assumes that there are four boron species corresponding to B(OH)3, B(OH)4–, B3O3(OH)4– and B4O5(OH)42– along with OH– in the solution. The model II assumes only one boron species B(OH)4– in the solution. The calculated solubilities are in accordance with the experimental data in the ternary systems NaCl–NaB(OH)4–H2O and Na2SO4–NaB(OH)4–H2O. The assumption of only one boron species B(OH)4− can be applied in the solubility calculation for the systems containing metaborate. The distribution of four boron species were obtained with model I in the borate solution. The mole fraction of the four boron species are mainly affected with the total boron concentration in the solution, but rarely effected by the concentration of Cl– and SO42–. B(OH)4− is the dominant boron species in the metaborate solution. The phase diagram and Pitzer model for the quaternary system were then used to conduct evaporation simulation. The evaporation-crystallization route and order of salt precipitation during the evaporation were demonstrated. The results of the evaporation simulation of brine can be used as a theoretical reference for salt separation and purification from brine resources.

Keywords

• Pitzer thermodynamic model
• Solid and liquid equilibrium
• Boron species
• Metaborate
• Evaporation simulation