Simultaneous Correlation of Liquid−Liquid, Liquid−Solid, and Liquid−Liquid−Solid Equilibrium Data for Water + Organic Solvent + Salt Ternary Systems:  Hydrated Solid Phase Formation

Abstract

The condensed phase equilibrium behavior of water + organic solvent + salt systems, when different hydrates are formed in the solid phase, increases the number of equilibrium zones, substantially complicating the simultaneous correlation of the equilibrium data in all the existing regions. In this paper, a procedure to perform the correlation of this type of system is presented in great detail, using, as an example, the water + 1-butanol + LiCl ternary system, where the salt appears in two forms: anhydrous and monohydrated (LiCl·H2O). To this end, the non-random two-liquid (NRTL) model for the excess Gibbs energy (G E) has been implemented, because the assumption of an electrolytic character for the solution in the liquid phase, despite being potentially more correct physically, does not give more flexibility to the G E function, as was discussed in a previous work. The common tangent plane criterion is used as an equilibrium condition to determine the equilibrium compositions in all the regions. The results obtained show the limitations of the NRTL equation to model this type of system, as a consequence of its lack of flexibility, in terms of the topological concepts that are related to the Gibbs energy of mixing (G M) function and the tangent plane criterion.

Correlation of the liquid–liquid equilibrium data for specific ternary systems with one or two partially miscible binary subsystems

“…A robust algorithm, proposed by the authors previously, and which has provided good results in the correlation of the equilibrium data for other special systems such as island-type ternary systems [5], or liquid-solid (LS) and liquid-liquid-solid (LLS) equilibrium data [6], has been used for this purpose. Acceptable representation of the LLE data for all systems has been achieved using the NRTL model.…”

Gibbs energy based procedure for the correlation of type 3 ternary systems including a three-liquid phase region

“…The above results illustrate the necessity of developing new more capable models able to reproduce the equilibrium behaviour of these complex systems accurately [21,22], as in the case of type 3 ternary systems including a LLLE region.…”

Methods for improving models for condensed phase equilibrium calculations

“…In the data collection, this system is not correlated with the NRTL model. In a previous work [26] the binary tie-lines (LLE) and the tietriangle (LLLE) were simultaneously correlated with NRTL showing that the very narrow LLLE tie-triangle and the LLE data for the 1-2 binary subsystem could not be simultaneously correlated with enough accuracy, though the behaviour could be represented qualitatively. Fig.…”

“…The previously developed methods [22][23][24][25][26] resulted in a robust computer program that has allowed the determination of the capabilities and limitations of the NRTL equation [27] for correlating equilibrium data between condensed phases in ternary systems. NRTL equation was selected as representative of thermodynamic local composition models, and is one of the most frequently used model.…”

“…In previous papers [22][23][24][25][26] robust calculation methods, based on the topological analysis of the Gibbs energy of mixing function (g M = ( mix G)/RT ), were developed. The topological analysis of g M is a valuable tool that allows deducing the geometrical conditions that the g M function has to fulfil, in order to reproduce certain equilibrium behaviour in the whole composition diagram, and clearly evidences any existing calculation inconsistency.…”