Intensified solvent extraction of L-tryptophan in small channels using D2EHPA

Abstract

The continuous extraction of an amino acid, L-tryptophan, from aqueous solutions was studied in small channels with diameters of 0.5 and 2 mm. L-tryptophan was separated from nitric acid solutions into hexane using Di(2-ethylhexyl)phosphoric acid (D2EHPA) as extractant. It was found that the plug flow dominated in the flow pattern map at mixture velocities below 0.1 m/s and all organic phase volume fractions in the 0.5 mm channel, while it appeared at mixture velocities below 0.02 m/s and organic phase volume fractions below 60% in the 2 mm channel. During plug flow, the specific interfacial area increased with mixture velocity and acquired maximum values of 4432 and 1456 m2/m3 in the 0.5 and 2 mm channels, respectively. Extraction efficiencies and percentage of up to 95% and 50% were reached in the 0.5 mm channel for residence times less 45 s, while both values were about 5–10% less in the 2 mm channel. Mass transfer coefficients of up to 0.16 and 0.13 s−1 were reached in the 0.5 mm and 2 mm channels, respectively.