Phase behaviour at different temperatures of ionic liquid based aqueous two-phase systems containing {[Bmim]BF 4 + salt sulfate (Zn 2+ or Ni 2+ ) + water} Cínthia das Dores Aguiar, Poliana Aparecida Lopes Machado, Bruno Giordano Alvarenga, Nelson Henrique Teixeira Lemes, Luciano Sindra Virtuoso ⇑ Colloid Chemistry Group, Chemistry Institute, Federal University of Alfenas (UNIFAL-MG), Rua Gabriel Monteiro da Silva, 700, Zip Code 37130-000 Alfenas, MG, Brazil article info Article history: Received 7 December 2015 Received in revised form 10 January 2017 Accepted 12 January 2017 Available online 14 January 2017 Keywords: Aqueous two-phase system based in ionic liquid Liquid-liquid equilibrium Ion exchange Thermodynamic parameters of mixture abstract Phase diagrams and liquid + liquid equilibrium (LLE) data of aqueous two-phase systems (ATPSs) com- posed of the {1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF 4 ) + zinc sulfate (ZnSO 4 ) or nickel sulfate (NiSO 4 ) + water} systems have been determined experimentally at T = (283.15, 298.15, and 313.15) K. The effect of the temperature, composition, cation and ion exchange in the formation this ATPS were available. The temperature had a remarkable effect on the position of phase diagrams. The decrease in temperature promoted phase segregation indicating the exothermic character of formation of these ATPSs and there was phase inversion at a temperature of 283.15 K for both. A scale was estab- lished to evaluate the ability of different cations of sulfate salts to induce the formation of ATPSs in mix- tures involving [Bmim]BF 4 . Thermodynamic parameters of hydration were used together with experimental results of saturation solubility to make various adjustments that seem to show that the molar entropy of hydration is the driving force for the separation process. Thermodynamic parameters of transfer of components (cations, anions and water) between the phases were also calculated from the experimental values and indicated that the material transfer of the bottom phase to the top is not spontaneous and tends to be less spontaneous as the TLL value increases. It was experimentally observed that no significant exchange of ion pairs occurs in the phase separation process. Additionally, the binodal curves were fitted to an empirical non-linear expression and the salting out effect was explored using the type-Setschenow equation. Data consistencies were tested using the Othmer-Tobias and Bancroft equations. Ó 2017 Elsevier Ltd. 1. Introduction Phenomena involving segregation of phases are often observed in mixtures of two or more components and play a central role in technological processes involving extraction, purification and/or pre-concentration of specific solutes [1]. Particularly, the so- called aqueous two-phase systems (ATPSs), which contain high water content in the equilibrium phases, have been considered a promising and environmentally safe alternative to replace the traditional separation processes that impact the environment due to the use of polluting substances [2]. In general, ATPSs are formed spontaneously when mixtures of aqueous solutions of chemically different polymers [3], or a poly- mer + inorganic salt [4], or even an ionic Liquid + inorganic salt [5], among other possibilities [6–9]. ATPSs feature a number of advantages compared to traditional methods of extraction/purifi- cation like easy scale-up, reusability of forming components and providing a biocompatible environment in two phases, which allow the use in separation processes of solutes of biotechnological interest that are susceptible to non-aqueous environments [10]. Moreover, the assembly and use of ATPSs involve low power con- sumption and are based on simple unit operations [11]. In recent years, ATPSs containing ionic Liquids (ILs) have been widely used due to their high extracting capacity of certain ana- lytes in relation to traditional ATPSs (formed by mixing polymer/ polymer or polymer/salt) [12]. The ILs are preferably used because of their low vapour pressure compared to traditional organic solvents and their excellent ability to solubilize both organic and inorganic compounds [13–15]. They also present low flammability and high stability due to their physical and chemical characteris- tics [16,17]. http://dx.doi.org/10.1016/j.jct.2017.01.008 0021-9614/Ó 2017 Elsevier Ltd. ⇑ Corresponding author. E-mail address: lsindrav@gmail.com (L.S. Virtuoso). J. Chem. Thermodynamics 108 (2017) 105–117 Contents lists available at ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct