Correlation of liquid–liquid equilibrium for binary and ternary systems containing ionic liquids with the tetrafluoroborate anion using ASOG Pedro A. Robles*, Luis A. Cisternas Department of Mineral Process and Chemical Engineering, University of Antofagasta, Angamos 601, P.O. Box 170, Antofagasta, Chile A R T I C L E I N F O Article history: Received 2 February 2015 Received in revised form 15 June 2015 Accepted 18 June 2015 Available online 29 June 2015 Keywords: Prediction Liquid–liquid equilibrium Ionic liquids ASOG Activity coefficient A B S T R A C T Ionic liquids are neoteric, environmentally friendly solvents (since they do not produce emissions) composed of large organic cations and relatively small inorganic anions. They have favorable physical properties, such as negligible volatility and wide range of liquid existence. Liquid–liquid equilibrium (LLE) data for systems including ionic liquids, although essential for the design, optimization and operation of separation processes, are still scarce. However, some recent studies have presented ternary LLE data involving several ionic liquids and organic compounds such as alkanes, alkenes, alkanols, water, ethers and aromatics. In this work, the ASOG model for the activity coefficient is used to predict LLE data for 15 binary and 09 ternary systems at 101.3 kPa and several temperatures; all the systems are formed by ionic liquids including the tetrafluoroborate anion plus alkanes, alkanols, water, ethers, esters and aromatics. New group interaction parameters were determined using a modified Simplex method, minimizing a composition-based objective function of experimental data obtained from literature. The results are satisfactory, with rms deviations of about 3%. ã 2015 Elsevier B.V. All rights reserved. 1. Introduction Over the past few years, research about ionic liquids has increased greatly, mainly in two directions: as reaction media, especially in homogeneous catalysis, and as solvents for separation processes [1,2]. Particularly for this latter purpose, their physical and chemical properties make them especially suitable as solvents, potentially substituting the most common volatile organic solvents in the chemical industry. Ionic liquids have very low vapor pressures [3–5]; this special characteristic of almost null vapor pressure has transformed ionic liquids into good alternatives as green solvents of future potential and high commercial interest. Liquid–liquid or solvent extraction is a major industrial process in the chemical industry that depends on the physical and chemical properties of a solvent to effect the separation of complex liquid mixtures, such as in the recovery of valuable products and the removal of contaminants in effluent streams. The separation potential and feasibility of solvents for commercial applicability are dependent on physical properties such as boiling point, thermal stability, viscosity, ease of recovery, toxicity and corrosive nature of the solvent. Liquid–liquid equilibrium data are essential for a proper understanding of extraction processes. The analysis of the composition of the two phases in equilibrium supplies consider- able information about mass balance and mass transfer calcu- lations in the design and optimization of separation processes. Liquid–liquid equilibrium (LLE) data for multicomponent systems including ionic liquids, although essential for the design and operation of separation processes, are still scarce. However, some recent studies [6–34] have presented binary and ternary LLE data involving several ionic liquids and organic compounds such as alkanes, alkanols, water, eter, esters and aromatics. Robles et al. [24–26] proposed in previous works the ASOG model for the activity coefficient in binary and ternary systems including ionic liquids with tetrafluoroborate (BF4), hexafluor- ophosphate (PF6) anions and imidazolium cation (Imid). In this work, LLE data for binary and ternary systems including ionic liquids with the tetrafluoroborate anion are correlated by a group-contribution model for the activity coefficient, the ASOG model [35–38]. New group interaction parameters were deter- mined by using a modified Simplex method, minimizing a composition-based objective function. The results are satisfactory, with rms deviations of about 3%. Abbreviations: ASOG, analytical solutions of groups; LLE, liquid–liquid equilibrium; RMS, root mean square absolute deviations; UNIFAC, universal functional activity coefficient; UNIQUAC, universal quasichemical activity coeffi- cient; Ref., reference. * Corresponding author. E-mail addresses: pedro.robles@uantof.cl, problesv@ucn.cl (P.A. Robles). http://dx.doi.org/10.1016/j.fluid.2015.06.025 0378-3812/ ã 2015 Elsevier B.V. All rights reserved. Fluid Phase Equilibria 404 (2015) 42–48 Contents lists available at ScienceDirect Fluid Phase Equilibria journal homepage: www.else vie r.com/locat e/fluid