Experimental andModeling of Densities, Viscosities,Refractive Indices, and Solubilities of MCl+PEG 4000+H2O (M = Li, Na, K) and MgCl2+PEG 4000+H2O Systemsat 298.15 K

In this study, densities, viscosities, and refractive indexes of unsaturated ternary systems MCl+PEG 4000+H2O (M = Li, Na, K) and MgCl2+PEG 4000+H2O were measured at 298.15 K. Additionally, for the latter system, solubility was measured at the same temperature. The Pitzer model was successfully used to fit the experimental data obtained for transport properties and solubilities, except for the viscosities of systems containing NaCl and KCl, which were best represented by Othmer’s rule. The refractive indices were well fitted to the model of Wang et al. Both density and refractive index increase progressively with increasing LiCl and PEG 4000 concentrations, while viscosity increases exponentially. The solubility decreases with increasing PEG 4000 concentration, following a trend similar to the common-ion effect. The polymer was considered a neutral species in the Pitzer model. Analysis of the solubility of the MgCl2+PEG 4000+H2O system and solubility values reported in the literature for the MCl+PEG 4000+H2O systems at 298.15 K indicates that, in an extractive crystallization process using PEG 4000, LiCl would remain in solution, while NaCl, KCl, and MgCl2 would crystallize. These results are useful in the design and simulation of brine processing and alternative separation processes for lithium extraction.