Prediction of salting‐out in liquid‐liquid two‐phase systems with ePC‐SAFT: Effect of the Born term and of a concentration‐dependent dielectric constant

Abstract

We dedicate this to honor the 60 th birthday of Prof. Christoph Janiak for outstanding networking activities and great research.Knowledge on phase equilibria is of crucial importance in designing industrial processes. However, modeling phase equilibria in liquid-liquid two-phase systems (LLTPS) containing electrolytes is still a challenge for electrolyte thermodynamic models and modeling still requires a lot of experimental input data. Further, modeling electrolyte solutions requires accounting for different physical effects in the electrolyte theory, especially the change of the dielectric properties of the medium at different compositions and the related change of solvation free energy of the dissolved ions. In a previous work, the Born term was altered by combining it with a concentration-dependent dielectric constant within the framework of electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT), and hence called 'ePC-SAFT advanced'. In the present work, ePC-SAFT advanced was validated against liquid-liquid equilibria (LLE) of LLTPS water + organic solvents + alkali halides as well as aqueous two-phase systems containing the phase formers poly (propylene glycol) and an ionic liquid. All the ePC-SAFT parameters were used as published in the literature, and each binary interaction parameter between ion-solvent was set to zero. ePC-SAFT advanced allowed quantitatively predicting the salt effect on LLTPS without adjusting binary interaction parameters, while classical ePC-SAFT or meaningless mixing rules for the dielectric constant term failed in predicting the phase behavior of the LLTPS.

Calculation of Multiphase Equilibria Containing Mixed Solvents and Mixed Electrolytes: General Formulation and Case Studies

“…The investigated IL has been modeled as a fully dissociated salt using the EoS ePC-SAFT advanced, 23,24 which includes a concentration-dependent dielectric constant and the Born term as a further contribution to the residual Helmholtz energy; this version has been used in a recent work to predict liquid−liquid equilibria containing dissolved ions. 72 The pure-component parameters of the ionic species and the neutral components used in this work are listed in the Supporting Information. The relative dielectric constant ε r of the IL-cation and the IL-anion was assumed to be ε r = 11, according to a previous work.…”

Solid–Liquid Equilibrium and Binodal Curves for Aqueous Solutions of NH3, NH4HCO3, MDEA, and K2CO3

“…Interaction parameters between CO 2 and MEA, n -methyldiethanolamine (MDEA), , piperazine, or ammonia have been obtained based on different types of phase equilibria (vapor pressure, vapor–liquid, and solid–liquid) and thermal (heat capacity and heat of absorption) data. ePC-SAFT has been used to model the mean ionic activity coefficient, the osmotic coefficient, the liquid–liquid equilibrium (LLE), and the density of alkali metal halides + organic solvent + water mixtures. − The model also provided an accurate prediction of the vapor–liquid equilibrium of sour gas and amine solvents using only parameters obtained from binary data . COSMO-RS-based models have also been successfully used to predict the solid–liquid equilibrium (SLE) and LLE of salt + water/organic solvent systems. − COSMO-based models can perform fully predictive calculations and are excellent tools for solvent screening applications; however, models with adjustable binary parameters (such as the extended UNIQUAC and ePC-SAFT) tend to present smaller deviation from experimental measurements.…”

“…ePC-SAFT has been used to model the mean ionic activity coefficient, the osmotic coefficient, the liquid–liquid equilibrium (LLE), and the density of alkali metal halides + organic solvent + water mixtures. − The model also provided an accurate prediction of the vapor–liquid equilibrium of sour gas and amine solvents using only parameters obtained from binary data . COSMO-RS-based models have also been successfully used to predict the solid–liquid equilibrium (SLE) and LLE of salt + water/organic solvent systems. − COSMO-based models can perform fully predictive calculations and are excellent tools for solvent screening applications; however, models with adjustable binary parameters (such as the extended UNIQUAC and ePC-SAFT) tend to present smaller deviation from experimental measurements. In this respect, SLE data shed light on the limits of solid formation in a given mixture and provide reliable data for estimating water activity, which strongly affects the estimation of water loss in the stripping column.…”

Prediction of pH in multiphase multicomponent systems with ePC-SAFT advanced

“…It is important to note that no binary interaction parameters were fitted for pairs that involve ionic species; such k ij values were all set to zero according to experiences from previous publications. 16,26 Most importantly, no parameters were fitted to the experimental pH values considered in this work. The input data were the pK a values and dielectric constants (Tables S4 and S5 in ESI †).…”

“…13 It was validated by sour gas solubility in reactive systems, 14 salt solubility in organic solvents, 15 and prediction of the salting-out in liquid–liquid two-phase systems. 16 In this work, this newest ePC-SAFT development (‘ePC-SAFT advanced’) was used to predict pH values for aqueous systems CO 2 + water (+ salt) and carboxylic acid + water + organic solvents. The considered systems form two phases (one liquid and one vapor L–V, or one liquid aqueous and one liquid organic phase L–L), and they involve dissociation of the present electrolytes.…”