Thermodynamics of the LiCl + H₂O System

Abstract

Literature data for the solubility of lithium chloride salts (anhydrous LiCl, LiCl‚H 2 O, LiCl‚2H 2 O, LiCl‚ 3H 2 O, and LiCl‚5H 2 O) in pure water have been compiled and critically evaluated. These data have been represented by empirical temperature-molality expressions from which the coordinates of the eutectics and of the peritectics have been calculated. The thermodynamic properties of the LiCl salts have been calculated from their solubilities in pure water using two different models of aqueous LiCl solutions (Pitzer's ion interaction model and the mean spherical approximation model) which allow the calculation of the activity of water and of the LiCl(aq) activity coefficient to very low temperatures (199 K) and/or very high concentrations (up to 30 M), characteristic of the LiCl + H 2 O system. The water-ice equilibrium constant has been determined to 199 K. Results of the Pitzer-Holmes-Mesmer ion interaction model are reliable only for LiCl molalities below 11 M. At higher molalities (corresponding to the solubilities of LiCl‚2H 2 O(s), of LiCl‚H 2 O(s), and of anhydrous LiCl for temperatures between 273 and 433 K), the mean spherical approximation model has been used. Entropies and standard enthalpies of formation of the various solids have been retrieved from fits of their solubility products with respect to temperature. Our values are in good agreement with the NBS values. There is a linear correlation between the entropies and standard enthalpies of formation and the number of water molecules in the LiCl hydrates, as already reported for MgCl 2 ‚nH 2 O, MgSO 4 ‚nH 2 O, and Na 2 CO 3 ‚nH 2 O.

Thermodynamic study of the system (LiCl+CaCl2+H2O)

“…Based on the data for LiCl Á H 2 O (s) , the standard Gibbs free energy of formation of LiCl Á H 2 O (s) and LiCl (s) has been calculated also. The calculated value of D f G LiClÁ2H 2 O in this work is equal to that reported by Monnin [25], however, the value D f G LiCl in this work is only similar to that given by Wagman [24] and quite different from that by Monnin [25]. In our recent work [26], we have compared the experimental water activity at saturation concentration at temperatures higher than T = 298.15 K and that calculated by the MSA model parameters given by Monnin et al [25], finding large difference between them.…”

“…The calculated value of D f G LiClÁ2H 2 O in this work is equal to that reported by Monnin [25], however, the value D f G LiCl in this work is only similar to that given by Wagman [24] and quite different from that by Monnin [25]. In our recent work [26], we have compared the experimental water activity at saturation concentration at temperatures higher than T = 298.15 K and that calculated by the MSA model parameters given by Monnin et al [25], finding large difference between them. Although the MSA model parameters given by Monnin et al [25] can represent the water activities of the system (LiCl + H 2 O) up to solubility limit at T = 298.15 K, they are invalid at higher temperatures at salt concentrations up to saturation points.…”

“…In our recent work [26], we have compared the experimental water activity at saturation concentration at temperatures higher than T = 298.15 K and that calculated by the MSA model parameters given by Monnin et al [25], finding large difference between them. Although the MSA model parameters given by Monnin et al [25] can represent the water activities of the system (LiCl + H 2 O) up to solubility limit at T = 298.15 K, they are invalid at higher temperatures at salt concentrations up to saturation points. Thus, their derived standard Gibbs free energy of formation of LiCl could be also inaccurate.…”

Electro-osmosis and Water Uptake in Polymer Electrolytes in Equilibrium with Water Vapor at Low Temperatures

“…Low water contents are also unavailable as LiCl solutions are bounded by solubility and the precipitation of salts at low water activities. 35 Our measurements at 30°C for 1100 equivalent weight ͑EW͒ Nafion resulted in values between those reported in the literature, 1.0 Ͻ Ͻ 1.5. 16,17 However, run to run deviations prevent us from presenting a statistically significant result at these higher temperatures.…”

Molecular Simulation of Aqueous Electrolyte Solubility. 3. Alkali-Halide Salts and Their Mixtures in Water and in Hydrochloric Acid

“…Solubility of Alkali-Halide Salts in Water, m, Calculated by OEMC Using Three Sets of Joung and Cheatham's Molecular Models of Ions Compatible with Three Water Models, 8 Compared with Experimental Values17 and Results of the Henry Convention Ideal Solution Model, at T = 298.15 K, P = 1 bar, and Externally Imposed Solid Molar Chemical Potentials, μ(s) a The values for μ(s) were taken from the NBS tables 5 (NBS) and from Monnin et al18 (M) where indicated; otherwise, they were taken from the NIST-JANAF tables. 3 * denotes results for systems with poor convergence, which are discussed in the text.…”