Density, pH, and Boron Species in the Ternary System NaBO2–Na2SO4–H2O at 298.15 K and 323.15 K

Abstract

The densities and pH values in the system NaBO2–Na2SO4–H2O at 298.15 K and 323.15 K were investigated. Combining the equilibrium constants for different boron species, the distributions of six boron species in the mixed solution were calculated with total boron concentration and pH values. The molar fractions of the six boron species are mainly affected by the total boron concentration and temperature, but rarely affected by the concentration of SO42–. The dominant boron species in the mixed solution at the two temperatures is B(OH)4‒. The mole fraction of B(OH)3, B5O6(OH)4‒, and B3O3(OH)4‒ can be neglected. The polyborate ions are easier to form as the temperature increases. The results of distribution for boron species in this study and those with the Pitzer model can both be used to describe the distribution of boron species in the mixed solution.

Solid–Liquid Phase Equilibria and Boron Species Distribution in the Quaternary System LiCl–LiBO2–Li2B4O7–H2O at T = 323.15 K and P = 0.1 MPa

“…Assuming that the B(OH) 3 was the reactant, the boron species distribution can be calculated with pH values and the equilibrium constants for different boron species, which were described in detail in our previous work. 27,28 In the lithium borate solution, the exact metaborate and tetraborate ions in the solution exist in the form of B(OH) 4.…”

“…At least six boron speciesB­(OH) 3 , B­(OH) 4 – , B 3 O 3 (OH) 4 – , B 3 O 3 (OH) 5 2– , B 4 O 5 (OH) 5 2– , and B 5 O 6 (OH) 4 – were found in the borate solution, which were confirmed by Raman spectra in the borate solution. ,− The distribution of boron species was affected by the total boron concentration, cation, temperature, and pH value. Assuming that the B­(OH) 3 was the reactant, the boron species distribution can be calculated with pH values and the equilibrium constants for different boron species, which were described in detail in our previous work. , In the lithium borate solution, the exact metaborate and tetraborate ions in the solution exist in the form of B­(OH) 4 – and B 4 O 5 (OH) 4 2– . − However, BO 2 – and B 4 O 7 2– were used for convenience.…”