Density, viscosity, refractive index and electrical conductivity of saturated solutions of the lithium hydroxide + ethanol + water system at 298.15 K, and thermodynamic description of the solid–liquid equilibrium

The water + ethanol + lithium hydroxide system has a great potential for implementing drowning-out crystallization processes in industrial lithium hydroxide production. For this reason, a knowledge of both the most relevant physical properties as well as the thermodynamic description of the solid–liquid equilibrium of this system is of great interest for designing industrial applications. In this paper, the density, viscosity, refractive index and electrical conductivity of the saturated solutions of water + ethanol + lithium hydroxide at 298.15 K were measured for different mass fractions of ethanol/solution in a range from 0 to 0.6. Equations are given for the values of the measured properties as a function of the mass fraction of ethanol. The phase diagram at 298.15 K was determined and its regions were illustrated. Under our experimental conditions, the precipitated salt was, in all cases, LiOH·H2O. Finally, a thermodynamic description of the solid–liquid equilibrium of the ternary system is provided based on the Chen model for calculating the mean ionic activity coefficients. This approach requires nine binary interaction parameters for a ternary system. Here, only the three binary interaction parameters corresponding to the LiOH + ethanol system were fitted, while the six remaining parameters (those corresponding to the water + ethanol and LiOH + water systems, respectively) were taken from previous published values.