Thermodynamic and Dynamic Modeling of the Boron Species in Aqueous Potassium Borate Solution

Abstract

The concentration of B(OH)3, B(OH)4-, B3O3(OH)4-, and B4O5(OH)42- in the solution and the solubilities in the system KCl-K2SO4-K2B4O7-H2O and its subsystems were calculated on the basis of the Pitzer model. The mole fraction of the four boron species is mainly affected by m(B) in the solution but less by m(Cl-) and m(SO42-). m(Cl-) and m(SO42-) mainly affect the solubility of K2B4O5(OH)4·2H2O. The calculated solubilities in the system KCl-K2B4O7-H2O agree well with the experimental data. The results show that the standard chemical potentials of K2B4O5(OH)4·2H2O at 298.15 K obtained in this work is reliable. The transformation between the boron species at 298.15 K was also conducted with the density functional theory (DFT) method. The results affirm that the boron species can transform other boron species as the boron concentration in the solution changes.