Niti Sunsandee

Selective enantioseparation of levocetirizine via a hollow fiber supported liquid membrane and mass transfer prediction

The enantioselective separation of levocetirizine via a hollow fiber supported liquid membrane was examined. O,O′-dibenzoyl-(2R,3R)-tartaric acid ((−)-DBTA) diluted in 1-decanol was used as a chiral selector extractant. The influence of concentrations of feed and stripping phases, and extractant concentration in the membrane phase, was also investigated. A mathematical model focusing on the extraction side of the liquid membrane system was presented to predict the concentration of levocetirizine at different times. The extraction and recovery of levocetirizine from feed phase were 75.00% and 72.00%, respectively. The mass transfer coefficients at aqueous feed boundary layer (kf) and the organic liquid membrane phase (km) were calculated as 2.41×102 and 1.89×102 cm/s, respectively. The validity of the developed model was evaluated through a comparison with experimental data, and good agreement was obtained.

Enantioselective Separation of Racemic Amlodipine by Two-Phase Chiral Extraction Containing O,O′-Dibenzoyl-(2S,3S)-Tartaric Acid as Chiral Selector

A two-phase chiral extraction system containing O,O′-dibenzoyl-(2S,3S)-tartaric acid ((+)-DBTA) in 1-decanol organic phase and aqueous phase was developed for the chiral resolution of amlopidine. The effects of extractant concentration, equilibrium time, and pH of the aqueous phase on the separation performance were investigated. The results indicated that the system afforded a strong chiral separation ability; the (+)-DBTA showed a higher recognition ability toward (S)-amlodipine than the (R)-amlodipine. Upon a single extraction, the enantiomeric excess (%) of (S)-amlodipine could be enriched to 24.27%. The product recovery ratio was 0.74. The distribution ratios for (S)-amlodipine (D S ), (R)-amlodipine (D R ) and separation factor (α) were 1.28, 0.78, and 1.64, respectively. Therefore, the pH and concentration of the extractant have the great effects on chiral separation ability. Two-phase chiral extraction has great significance for preparative separation of (S)-amlodipine; it can also be used to design and scale up the enantioselective separation process.

Synergistic Enantioseparation of Rac-Phenylalanine via Hollow Fiber Supported Liquid Membrane

The enhancement in the separation of rac-phenylalanine in an aqueous medium was well achieved by a synergistic extractant through a hollow fiber supported liquid membrane (HFSLM). Chiral extractant (O,O′-dibenzoyl-(2S,3S)-tartaric acid ((+)-DBTA)) was employed in combination with a non-chiral extractant (either di-2-ethylhexyl phosphoric acid (D2EHPA) or tricaprylmethylammonium chloride (Aliquat 336)). While n-octanol and de-ionized (DI) water was used as an organic solvent and a stripping solution, respectively. The synergistic effect from the combined (chiral and non-chiral) extractant was reported. The strongest synergistic effect on the separation of L-phenylalanine was observed when the ratio of chiral and non-chiral extractant equaled 1:1. From this work of a separation via HFSLM, the highest enantiomeric excess (% e.e.) of L-phenylalanine was reported to 80% from the combined extractant between (+)-DBTA and D2EHPA (6 mmol/L) and pH 5.0. The extraction and stripping of L-phenylalanine was 98% and 92.50%, respectively.

Separation of yttrium from rare earth using hollow fiber-supported liquid membrane: factorial design analysis

AbstractThe selective separation of yttrium ions from other rare earth elements using a hollow fiber-supported liquid membrane was performed. The extractant was Cyanex272 and the stripping solution was nitric acid. Yttrium was extracted preferentially in comparison to other rare earth elements. The pH and flow rate of the feed solution, as well as the concentration of Cyanex272, were regarded as factors in the experiments. A 23 factorial design was used to determine the significant factor, their interaction, and optimized condition. Linear regression model and surface response were applied to predict the percentages of extraction of yttrium at different values of significant factors. The validity of linear regression model was evaluated through a comparison with experimental data, with good agreement achieved.

Factorial design in optimization of the separation of uranium from yellowcake across a hollow fiber supported liquid membrane, with mass transport modeling

The extraction and stripping of uranium(VI) from other impurity elements in yellowcake was performed simultaneously in one stage by a hollow fiber supported liquid membrane. Uranium ions were selectively extracted from yellowcake using TBP as the extractant, while thorium and some rare earth elements were rejected in the raffinate. The optimization method was carried out using 32 factorial design. The concentration of nitric acid in the feed solution and the concentration of TBP in the liquid membrane were regarded as factors in the optimization. A mass transport model focusing on the boundary layer of the extraction side was also applied. The model can predict the concentration of uranium in the feed tank at different times. The validity of the developed model was statistically evaluated through a comparison with experimental data, and good agreement was obtained.