Determination and correlation of phase equilibria of chiral magnetic ionic liquid aqueous two-phase systems with different inorganic salts at 298.15 K

Abstract

Three novel chiral magnetic ionic liquids (MILs) with L-Pro anion were synthesized and applied to construct chiral magnetic ionic liquid aqueous two-phase systems (chiral MILATPs). This is the first reported chiral MILATPs and is showing great potential in the extractive resolution of racemic amino acids. In this work, aqueous two phase equilibrium binodal data of these chiral MILATPs ([CnMIM-Tempo][L-Pro](n = 2–4) + K2CO3/K3PO4/Na2CO3/Na2SO4 + H2O) were measured at temperature of 298.15 K. Three classical empirical equations including Merchuk equation were applied for the correlation of the experimental binodal data to obtain the binodal curve. Satisfactory correlation performances were achieved. The screening of inorganic salt revealed that K2CO3 and K3PO4 are better salting-out reagents than Na2CO3 and Na2SO4. Investigation of chiral MIL species demonstrated that chiral MIL with longer alkyl chain length of cation has better phase forming ability when the values of n are in the ranges of 2–4. Moreover, tie-line data for systems containing K2CO3 or K3PO4 were measured and correlated by Othmer-Tobias equation with satisfactory fitting performances (all R2 higher than 0.99). These results has ensured the reliability of these experimental data. The phase behaviors of these chiral MILATPs in this work has proved to meet the need of practical application and all these tested aqueous two-phase equilibrium data as well as the corresponding thermodynamic fitting can provide us useful reference for the future application in the field of extractive resolution of racemic amino acids.