Ura Pancharoen

A Reaction Flux Model for Extraction of Cu(II) with LIX84I in HFSLM

Hollow fiber supported liquid membrane (HFSLM) is a favorable method to extract both valuable compounds and heavy metal pollutants such as chromium, copper, and nickel at a very low concentration. In this work, the extraction of Cu(II) by LIX84I dissolved in kerosene was theoretically and experimentally investigated. A model to estimate the percentage of extraction of copper ions from synthetic water considering the effect of reaction flux in membrane phase of the HFSLM system was studied. H2SO4 solution was used as the stripping solution. The facilitated transport mechanism of the chemical reaction at the feed-membrane interface was taken into account in the model equations. The percentage of copper ion extraction was plotted against its initial concentration in feed and also feed flow rate. Subsequently, the separation time and separation cycle were determined in accordance with the simulated values of copper ion concentration and the feed flow rate from the model. The modeled results were in good agreement with the experimental data at the average percentage of deviation about 2%.

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.

Extractive reaction for epoxidation of cyclohexene to cyclohexene oxide using dioxirane in ketone/Oxone® system

Abstract Extractive reaction for the epoxidation of cyclohexene to cyclohexene oxide using dioxirane was studied. The studies were divided into two main parts: (1) comparison of different cyclohexene oxide preparation methods and (2) effects of operating parameters such as stirring rate, type of solvent, initial solvent/aqueous ratio, temperature, pH and amount of catalyst on the performance of the extractive reaction. The results revealed that the best method was the epoxidation of cyclohexene by dioxirane in an extractive reaction system with presence of a phase transfer catalyst. A maximum conversion obtained from the system without a solvent can be exceeded with an extractive reaction process by introducing of an immiscible solvent to the system. It was found that the cyclohexene oxide yield increased with increasing stirring rate and the amount of acetone, and that the reaction system using dichloromethane showed the highest performance compared to those with toluene and benzene.

Selective Transport of Palladium through a Hollow Fiber Supported Liquid Membrane and Prediction Model Based on Reaction Flux

This paper describes the application of hollow fiber supported liquid membranes for the simultaneous extraction and recovery of low-concentration palladium from waste aqua regia solutions. A mathematical model to predict the palladium transport was also developed and verified. We found that the optimum conditions for transport of palladium were pH 2 in the feed with 0.005 M thioridazine and 0.05 M oleic acid in liquid membrane, 0.03 M NaNO2 in the stripping solution, and an operating flowrate of 100 mL/min. With thioridazine and oleic acid as the extractant carrier, a synergistic enhanced extraction was observed. By employing a 3-cycle operation in repeated operating cycle mode, the cumulative palladium extraction and recovery was 82% and 78% respectively. Our mathematical model was developed based on reaction flux. The reaction order and the rate constant were determined. It revealed that the first order rate law governed the reaction system for both the extraction and the recovery. The extraction rate constant (k f ) and the stripping rate constant (k s ) were calculated to 0.0140 s−1 and 0.0248 s−1, respectively. The model was set up for a scenario based on a varying flowrate and a repeated operating cycle mode. The results showed good agreement with theoretical data (curve fittings gave R2 > 0.9).

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.

Arsenic Removal from Natural Gas Condensate using a Pulsed Sieve Plate Column and Mass Transfer Efficiency

This work applied a pulsed sieve plate column in conjunction with liquid-liquid extraction technique to remove arsenic from natural gas condensate. The relevant parameters, that is the type and concentration of the extractant, pulse velocity, volumetric-flow rate ratio of the condensate to the extractant, operating time, and extraction cycle were investigated. Mass transfer efficiency in terms of the overall height of transfer unit (HTU oy , cm) and the interfacial area (m2/m3) were calculated. The highest percentage of arsenic removal in this study was 94% corresponding to the calculated HTU oy of 26 cm and the calculated interfacial area of 118 m2/m3 at the optimum conditions: the mixture of the extractant (1 M hydrochloric acid and 20% (v/v) methanol), pulse velocity of 20 mm/s, and volumetric-flow rate ratio of the condensate to the extractant of 1:4. By using continuous operation in the cycle mode, the percentages of arsenic removal were observed at 94, 85, and 80 from the respective 1st, 2nd, and 3rd cycles. The operation was based on the condition that fresh feed was introduced in each cycle while the extractant was reused.

Modelling and experimental validation of enantioseparation of racemic phenylalanine via a hollow fibre-supported liquid membrane

This paper reports on the enantioseparation of racemic phenylalanine or D-phenylalanine and Lphenylalanine via a hollow fibre-supported liquid membrane (HFSLM) and the results are compared with the mathematical model. The enantioseparation results, of 80 % and 73 %, showed the highest extraction and stripping of l-phenylalanine from the feed phase and the enantiomeric excess (% ee) of 60 % from 6 mmol L−1 of initial rac-phenylalanine in the feed solution. The optimum parameters were feed solution at pH 5, 6 mmol LL−1 of O,O′-dibenzoyl-(2S,3S)-tartaric acid ((+)-DBTA) as the extractant in octanol as the liquid membrane, and deionised water as the stripping solution. Equal flow-rates of feed and stripping solutions of 100 mL minL−1 were adjusted in a batch operation mode for 50 min at ambient temperature. From the calculation, the equilibrium constants of extraction (Kex) and mass transfer coefficients in the feed phase (kf) and in the liquid membrane phase (km) were found to be 1.81 L mmol−2, 3.50 × 10−2 cm s−1, and 1.40 × 10−2 cm s−1, respectively. Finally, the change in concentrations of d,l-phenylalanine over time in the feed and stripping solutions by mathematical model were estimated and compared with the experimental results. The values thus calculated were in agreement with the experimental data with the average deviation of approximately 3 %.