Thermodynamic study of ATPS involving ethyl lactate and different inorganic salts

Abstract

In this work, three Aqueous Two-Phase Systems (ATPS) involving ethyl lactate and the inorganic salts (NH4)2SO4, K2HPO4 and NaH2PO4 have been studied. To analyse the separation process, binodal curves and tie lines were experimentally determined at T = 298.15 K and atmospheric pressure. The experimental binodal data were successfully fitted using several empirical equations: Merchuk et al., Hu et al., Han et al. and Jayapal et al., and the degree of consistency of the tie line compositions was evaluated using Othmer-Tobias and Brancoft equations. The liquid–liquid equilibria were fitted using the Pitzer-Debye-Hückel + UNIQUAC and the UNIQUAC thermodynamic models. For all systems, the modelled tie lines were very similar to the experimental ones, but the first model presented somewhat smaller deviations, which allows to conclude that long-range forces present in these systems with strong salts should be considered.