Prakorn Ramakul

Separation of Co(II) and Ni(II) from thiocyanate media by hollow fiber supported liquid membrane containing Alamine300 as carrier — investigation on polarity of diluent and membrane stability

The separation of cobalt(II) and nickel(II) ions by HFSLM has been presented. The feed solution is 0.5M thiocyanate containing 300 ppm each of cobalt(II) and nickel(II) ions, whereas extractant is Alamine300 and the stripping solution is ammonia. Cobalt(II) is more preferable with Alamine300 than nickel(II). The effects of pH, Alamine300 concentration and ammonia concentration were investigated. Seven diluents were used: hexane, decanol, chlorobenzene, benzene, dichloromethane, ethylene dichloride and chloroform with different polarity indexes, from 0.1–4.1. Nickel(II) ion which is unpreferable with Alamine300 was used as a tracer to determine the membrane stability. The polarity of the diluents was found to be the main factor influencing the extraction performance and stability of a liquid membrane. The decreasing of polarity of the diluent can prolong the membrane stability, but the percentages of extraction and stripping decreased. The longest lifetime, 200 minutes, was obtained by using hexane as a diluent with the polarity index of 0.1.

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.

Application of hollow fiber supported liquid membrane as a chemical reactor for esterification of lactic acid and ethanol to ethyl lactate

Hollow fiber supported liquid membrane was applied as a reactor to synthesize ethyl lactate from lactic acid. Lactic acid in the feed solution was extracted by tri-n-octylamine (TOA) and stripped by ethanol with p-toluene sulfonic acid acting as the catalyst to form ethyl lactate. Central composite design (CCD) was used to determine the significant factors and their interactions. The response surface was applied for optimization. An optimized yield of 30% was predicted and its validity was evaluated by comparison with experimental results at different concentrations of lactic acid in the feed solution, with good agreement achieved.

Salt effect on the liquid-liquid equilibrium of water-furfuryl alcohol-furfural system at 298.15 K

Salt effect on the liquid phase equilibrium of the water-furfuryl alcohol-furfural system at 298.15 K was studied. The effects of salt concentration (1, 3 and 10% w/wNaCl) and type of salt (LiCl, KCl and RbCl) were investigated. The solubility and tie-line data of these systems were determined by experimental analysis. The results showed that addition of salt significantly affected the two-phase region of ternary system; the enlargement of two-phase region occurred with an increase of salt concentration in initial aqueous phase and the type of the salt in the following order: LiCl>NaCl>KCl>RbCl. Distribution coefficients and separation factors were also calculated. The reliability of the LLE experimental results was validated by the Othmer-Tobias equation, Hand equation and Bachman equation. NRTL was employed to correlate the results obtained by the modeling with the experimental data. Good correlation result was confirmed by the rmsd values of less than 0.3%.

Separation of mercury and arsenic from produced water via hollow fiber contactor: Kinetic and mass transfer analysis

The separation of Hg(II) and As(V) from produced water by hollow fiber contactors was investigated. Two identical hollow fiber modules were employed. The first module was used for extraction, while the second module was used for stripping. The optimum conditions achieved were 14% (v/v) of Aliquat336, 0.07 M thiourea, volumetric flow rate of 100 mL/min for aqueous solution and 0.02 M HCl of stripping solution. At such conditions, the maximum extraction of Hg(II) and As(V) attained 100% and 78.78%, respectively. Concurrently, the maximum stripping of Hg(II) and As(V) reached 47.88% and 6.66%, respectively. The overall mass transfer coefficients of Hg(II) and As(V) extraction were 2.31×10−6 and 1.15×10−6m/s, while the Hg(II) and As(V) stripping exhibited the overall mass transfer coefficients of 8.37×10−7 m/s and 9.05×10−7 m/s, respectively. Mass transfer coefficients of the organic layer diffusion (k0) had the most effect on the overall mass transfer coefficients.