Enthalpies of Solution of Sodium Chloride and Potassium Sulfate in Water. Thermodynamic Properties of the Potassium Sulfate + Water System

Abstract

An adiabatic calorimeter was used to measure enthalpies of solution into water of sodium chloride (∼0.13 mol‚kg -1 ) at nominal temperatures of 298.15 K, 303.15 K, and 308.15 K and of potassium sulfate (∼0.039 mol‚kg -1 ) at nominal temperatures of 298.15 K and 303.15 K. The results for sodium chloride were compared to a previous equation of state so as to validate the use of values from that equation of state for calibration of, or checks on the accuracy of, solution calorimeters. Thermodynamic properties from the literature for the potassium sulfate + water system and the present measurements were used to generate equations that represented the thermodynamic properties of this system from the freezing point of the aqueous solution to 500 K. The measured values included in the fitted equations spanned the range of temperature of approximately 271 K to 530 K for K 2 SO 4 (aq) and 13 K to 854 K for K 2 SO 4 (cr). New equations and/or values for the following properties are given in the present work: (1) thermal properties of K 2 SO 4 (cr) from 0 K to near the orthorhombic to hexagonal transition at 857 K, (2) the change in chemical potential for both K 2 SO 4 and H 2 O in K 2 SO 4 (aq) as a function of temperature and molality, valid from 271 K to 500 K, from 0 mol‚kg -1 to the saturation molality, and to pressures of 40 MPa, and (3) standard-state properties for the aqueous solution process.

Thermodynamic modeling of aqueous Na + –K + –Cl − –SO 4 2− quaternary system with electrolyte NRTL model

“…The model results agree well with the literature data across all temperatures. We also compare the model results with other available literature data [29,[34][35][36][37]. As shown in Table 3, the model results agree well with the data with the MRD values around 2%.…”

“…4 shows results at temperatures above 348.15 K. The results are consistent with the results on mean ionic activity coefficient. Comparisons with other literature osmotic coefficient data [34,35,[37][38][39] are summarized in Table 3. The MRD values are around 2%.…”

“…Heat capacity, C p , and liquid enthalpy, H l , of the liquid solution are calculated with the following equations: (20) Extensive thermodynamic data such as vapor pressure depression, molality scale mean ionic activity coefficient, osmotic coefficient, excess enthalpy, heat capacity, and salt solubility for aqueous K 2 SO 4 binary are available [28][29][30][31][32][33][34][35][36][37][38][39][40][41]. Table 3 shows some readily available literature data used in this study and their ranges of temperature and concentration.…”

“…It represents a simple and practical thermodynamic model for the K 2 SO 4 + H 2 O binary. In contrast, the Pitzer model requires up to 32 coefficients to account for both concentration and temperature dependences for aqueous K 2 SO 4 system[12,37].…”

Crystallization of potassium sulfate by cooling and salting‐out using 1‐propanol in a calorimetric reactor

“…Some research has been directed at the crystallization of potassium sulfate from aqueous solutions using MSMPR continuous crystallizers [1][2][3][4]. The kinetics of potassium sulfate from aqueous solutions of batch crystallization process has also been widely studied, following various techniques for measurements of dissolution rates, nucleation, and crystalline growth [5][6][7][8], as well as thermodynamic properties, [9].…”