Liquid–Liquid Equilibria of Water + 1-Butanol + Amino Acid (Glycine or dl-Alanine or l-Leucine) at 313.15 K

Abstract

Amino acids play an important role both in animal metabolism and in industrial processes. Since they are rarely found in nature in a free form, they must be obtained by biosynthesis or protein hydrolysis, often resulting in aqueous mixtures containing various solutes including several types of amino acids. As a consequence, the cost of the separation processes and concentration of amino acids can be as high as 90 % of their total manufacturing cost. In this way, the design of such processes requires knowledge of the partitioning behavior in two-phase systems and thermodynamic models should support this optimization procedure. However, both the complexity of biomolecules, due to their multiple functional groups, and the crucial role of water make the standard available thermodynamic models unattractive for the computation of phase behavior. Therefore, new thermodynamic models for the description of the phase behavior of systems containing biomolecules are required. In this work, liquid–liquid equilibrium data of the ternary systems 1-butanol + water + amino acid (glycine, dl-alanine or l-leucine) were measured at 313.15 K. The experimental results were correlated and interaction parameters were estimated for the modified-NRTL, UNIFAC and UNIFAC-Campinas models. The modified-NRTL model was able to describe the data better than the UNIFAC and UNIFAC-Campinas models.