Experimental and thermodynamic modeling study of the solid-liquid equilibrium in the ternary system (NaCl + NaClO3 + H2O) at 293.15 and 333.15 K and 0.1 MPa

The study of the solid-liquid phase equilibrium for (NaCl + NaClO 3  + H 2 O) system is of significance to understand the thermodynamic property of the aqueous solution of ionic membrane electrolysis process to promote the production of sodium hydroxide (caustic soda). The solubilities and the physicochemical properties including density, refractive index and pH for this ternary system at 293.15 and 333.15 K and 0.1 MPa were measured using the isothermal dissolution method. Based on Pitzer ion-interaction model and its extended HW model, the solubility equilibrium constants K sp of NaClO 3 and the mixing ion-interaction parameters ( θ Cl,ClO3 , Ψ Na, Cl,ClO3 ) at 293.15 and 333.15 K were parameterized in this work. The Debye-Hückel limiting slope A ø , the Pitzer single-salt parameters of NaCl and NaClO 3 and the solubility equilibrium constants K sp of NaCl at 293.15 and 333.15 K were taken from the relative temperature-dependence formula in the literature. A comparison shows that the calculated solubilities of the ternary system at 293.15 and 333.15 K agree well with the experimental data. The calculated results of densities and refractive indices using the empirical equations agree well with the experimental data at 293.15 and 333.15 K.