Continuous plug flow extraction of L-tryptophan using ionic liquid-based aqueous biphasic systems in small channels

Abstract

A double process intensification of the conventional solvent extraction was accomplished by employing two strategies. Firstly, by utilizing continuous small channels and secondly by replacing organic solvents with novel ionic liquid based aqueous biphasic systems (IL-ABS). The flow extraction of the amino acid L-tryptophan was investigated in small channels with internal diameters of 0.5 and 0.8 mm and three different IL-ABS. The partition coefficients for two different L-tryptophan concentrations (0.325 and 0.5 wt%) were measured for IL-ABS compositions 18, 20 and 22 wt% K3PO4 and C4mimCl. Increasing the weight composition of the conventional salt and the ionic liquid increased the partition of the amino acid for the top ionic liquid rich phase. The continuous extractions were carried out in the plug flow regime. Correlations were proposed for the plug length and the film thickness as functions of the capillary number. It was found that the extraction efficiency with the 20 wt% ABS reached 95 % in under 15 s in the 0.5 mm channel and in about 40 s in the 0.8 mm channel. When comparing the IL-ABS, the 22 wt% reached 96 % extraction efficiency in 14 s compared to the 70 s of the 20 wt% in the 0.8 mm channel. The overall mass transfer coefficients varied between 0.05 and 0.2 s−1 for all cases studied, which were significantly higher than those in conventional solvent extraction systems.