Measurement of Specific Heat Capacity of NaBO₂(aq) Solution and Thermodynamic Modeling of NaBO₂ + H₂O, NaBO₂ + NaCl + H₂O, and NaBO₂ + Na₂SO₄ + H₂O Systems

Abstract

The specific heat capacity of NaBO 2 (aq) solution was determined using a Calvet-type calorimeter at a temperature from 288.15 to 338.15 K and at a concentration from about 0.25 mol•kg −1 H 2 O to near room temperature solubility limit. Combining these specific heat capacity data and thermodynamic and solid−liquid equilibrium data reported in the literature, a temperature-dependent thermodynamic model was developed for the NaBO 2 + H 2 O system based on Pitzer−Simonson−Clegg activity coefficient equations. The model represents all of the properties over a wide temperature and concentration ranges. Combining the binary models of NaCl + H 2 O and Na 2 SO 4 + H 2 O systems published in the previous studies of our group, multitemperature thermodynamic models of the NaBO 2 + NaCl + H 2 O and NaBO 2 + Na 2 SO 4 + H 2 O systems were constructed. These ternary models reproduce the experimental solubility isotherms reported in the literature in general, but some significant inconsistency is still present. More accurate solubility data for these ternary systems at various temperatures are urgent.

Speciation and Phase Equilibria of Aqueous Boric Acid and Alkali Metal Borates from Ambient to Hydrothermal Conditions: A Comprehensive Thermodynamic Model

“…from natural resources. These include extensive solubility, speciation (pH and Raman spectroscopic), and calorimetric measurements. − All of these quantitative results are valuable sources of information that provide insights into the complex chemistry of aqueous boric acid and borate solutions and are an excellent foundation for the development of a more robust and reliable thermodynamic model for these systems. These data provide additional opportunities for testing and validating the model.…”