Multistage Liquid-liquid Extraction Research Articles

Enantioselective liquid-liquid extraction of 2-cyclohexylmandelic acid enantiomers using chiral ionic liquids.

Obtaining optically pure compounds in an eco-friendly and cost-efficient manner plays an important role in human health and pharmaceutical industry. Racemic separation using multistage stereoselective liquid-liquid extraction has become one of the most practical and effective approach to access homochiral enantiomers. Currently, chiral ionic liquids (CILs) with structural designability have become a promising chiral additive and enable them as adjustable candidates for racemic separation. Herein, a high-effective stereoselective liquid-liquid extraction process composed of imidazolium cations and amino acid-derived anions as the chiral additive was established for racemic 2-cyclohexylmandelic acid (CHMA) separation. We have systematically investigated the choice of organic solvent, concentration of CIL, extraction temperature, and the pH of aqueous phase. For three-stage stereoselective extraction, the maximum enantiomeric excess (e.e.) for CHMA was reached up to 40.6%. Furthermore, the mechanism of steric effect and stereoselective capacity between the CILs and racemic CHMA was discussed and simulated. We envision that the work will facilitate the development of CILs in multistage liquid-liquid extraction and promote the large-scale production of optically pure enantiomers.

Liquid-liquid extraction of calcium in a scaled-out microfluidic device: Process intensification using a crown ether-ionic liquid system

Solvent extraction of calcium was investigated in four microchannels parallelized on a microfluidic chip. Uniform flow distribution of observed flow patterns in parallel microchannels shows successful numbering-up of the microfluidic device. First, flow regime maps were plotted for six liquid-liquid systems. A parallel flow regime with complete phase separation was chosen as the desired flow regime for extracting the calcium ion. Organic phase and crown ether types were tested to obtain the maximum extraction of calcium from the aqueous phase. In these conditions, the effects of crown ether concentration, the concentration of calcium ion and pH were studied in order to optimize the extraction efficiency using the Box-Behnken method. The mass transfer coefficient was also determined as a function of residence time at different concentrations of calcium metal ions. In the second step, ionic liquid-based solvent extraction was studied. In this regard, the performance of the diluent (conventional organic solvent) type on the calcium separation efficiency was investigated. An excellent improvement in separation efficiency (7.1–64.2%) was achieved for the EMIM NTf2/n-butyl acetate mixture compared to butyl acetate. In the final step, continuous multistage liquid-liquid extraction of the calcium ion was performed using three series microchips to evaluate the microfluidic cascade's performance.

Dilute sulfuric acid hydrolysis of Chlorella vulgaris biomass improves the multistage liquid-liquid extraction of lipids

Chlorella spp. have been successfully cultured at commercial scale and show potential for the production of advanced biofuels. A current challenge in the downstream processing of Chlorella spp. is the sequential fractionation of whole biomass in different macromolecules such as lipids and carbohydrates. Herein, the biorefinery concept was used to evaluate the best sequence of extraction of carbohydrates and lipids of C. vulgaris. It is also important to develop biorefinery processes that produce green chemicals like ethanol because large volumes of solvents are required for lipid extraction. First, the extraction conditions were optimized to achieve maximum yields of carbohydrates and lipids separately. The extraction of carbohydrates was less complex than the multistage extraction of lipids from C. vulgaris. The use of ethanol and hexane mixture resulted in a lower extraction of lipids from C. vulgaris, even after 4 stages of extraction, and the final lipid content corresponded to only 65% of the lipids extracted with standard methods. Moreover, the multistage extraction of lipids did not improve the subsequent extraction of carbohydrates (lipids-carbohydrates route). However, the dilute sulfuric acid hydrolysis drastically improved the subsequent multistage extraction of lipids (carbohydrates-lipids route), and the lipid yield using this route was twice higher in comparison with the lipids-carbohydrates route. The hydrolysates obtained using the routes carbohydrates-lipids and lipids-carbohydrates showed levels of 2.6 ± 0.2 and 2.7 ± 0.1 g L−1 of total neutral carbohydrates, respectively. The different routes did not exert a great effect on the levels of inhibitors.

A Novel Hollow-Fiber Membrane Embedded Co-axial Microdevice for Simultaneous Extraction and Stripping

ABSTRACTHow to realize multistage liquid-liquid extraction in a single microdevice is a big challenge in micro-separation processes. No simple solution has been presented until now. In this work, we designed a hollow-fiber membrane-embedded co-axial microdevice with a controllable transmembrane pressure to realize a multistage extraction process successfully. Using the extraction of phenol as a model system, the steady liquid-liquid-liquid three-phase flow of the feed, extractant, and back-extractant was realized in the designed microdevice. By precisely controlling the pressure of the tube side, the extractant was separated from the feed in situ and passed into the shell side to contact with the back-extractant directly. In this way, both of the extraction yield and stripping yield reached 95%. And by introducing a transmembrane pressure with periodic oscillation, five theoretical stages were successfully achieved within 3 min residence time in the single microdevice. This technology may open a new area for microfluidic applications.

Fractionation of bio-oil produced from hydrothermal liquefaction of microalgae by liquid-liquid extraction

Fractionation of bio-oil is in favor of upgrading bio-oil to transport fuel or chemicals. The microalgae Dunaliella tertiolecta was hydrothermally liquefied to form a bio-oil, which was split into two layers during cooling: the lower layer contained organics with relatively high molar mass from 78 to 389 g mol−1, while the super layer with relatively low molar mass from 44 to 121 g mol−1. The lower layer of hydrothermally liquefaction (HTL) bio-oil was further fractionated into ethanol phase (oil 1) and dichloromethane phase (oil 2), and the super layer yielded 1 or 3-4 fractions of extracts (oil 3) via single-stage or multistage liquid-liquid extraction respectively. The compositions of each fraction were analyzed by GC-MS in detail. Dichloromethane, chloroform, cyclohexane, benzene, toluene, iso-octanol, petroleum ether, carbon tetrachloride, 1,1,1-trichloroethane, ethyl acetate were compared in terms of their extraction capabilities to organics of bio-oil. The results indicated the chloroform and dichloromethane have the highest comprehensive extraction capabilities. In multistage extraction, when dichloromethane was used as extractant, the extraction distribution ratio (calculated using COD, chemical oxygen demand) was 0.66 in first-stage, then sharply dropped with an increase in stage number, 2nd∼3rd stage extractions achieved the maximum extraction percentage (approximately 53%). That the optimum combination of chloroform, benzene and 1,1,1-trichloroethane fractionated the super layer of HTL bio-oil can obtain very low oxygen content fraction: hydrocarbons (purity of hydrocarbons: relative content 97.9%) from the 2nd stage of multistage extraction.

Construction and application of a model on the resolution of tropic acid enantiomers by enantioselective liquid-liquid extraction in centrifugal contactor separators

Abstract This paper reports on the construction and application of a mathematical model on multistage liquid-liquid extraction of tropic acid (TA) enantiomers in centrifugal contactor separators (CCSs). An efficient extraction system was obtained, where HE-β-CD and butyl acetate was selected as the best extractant and organic solvent. The mechanism of reactive extraction of TA enantiomers by HE-β-CD was proposed and the thermodynamic constants such as physical partition coefficient and reactive equilibrium constants were obtained, which combined with the law of mass conservation gave the basis for construction of the model. The model was applied to predict and optimize the symmetrical separation of TA enantiomers. The optimal condition was obtained as follows, O/W volume ratio of 3.0, pH of 3.00 and HE-β-CD concentration of 0.05 mol/L, where ee eq (equal enantiomeric excess) can reach up to 42%. The simulated results reveal that the minimum number of stages for ee eq > 97% and ee eq > 99% was 56 and 78, respectively.

Chiral separation by enantioselective liquid–liquid extraction

The literature on enantioselective liquid-liquid extraction (ELLE) spans more than half a century of research. Nonetheless, a comprehensive overview has not appeared during the past few decades. Enantioselective liquid-liquid extraction is a technology of interest for a wide range of chemists and chemical engineers in the fields of fine chemicals, pharmaceuticals, agrochemicals, fragrances and foods. In this review the principles and advances of resolution through enantioselective liquid-liquid extraction are discussed, starting with an introduction on the principles of enantioselective liquid-liquid extraction including host-guest chemistry, extraction and phase transfer mechanisms, and multistage liquid-liquid extraction processing. Then the literature on enantioselective liquid-liquid extraction systems is reviewed, structured on extractant classes. The following extractant classes are considered: crown ether based extractants, metal complexes and metalloids, extractants based on tartrates, and a final section with all other types of chiral extractants.

SEPARATION OF TAXANE COMPOUNDS BY LIQUID-LIQUID EXTRACTION

Experimental and numerical studies on liquid-liquid extraction of taxane compounds that are extracted from yew needles by solid-liquid extraction are carried out. In the treatment, the materials are classified to three components, and separation of component C from components A and B is discussed. In experiments, distribution coefficients and selectivities of those components are measured with various solvents. Based on the experimental results, numerical simulation of the countercurrent multistage liquid-liquid extraction process for separating the components is carried out with various operating conditions. Then, the fractional countercurrent multistage liquid-liquid extraction process is examined, and the effect of reflux operation on separation performance of the fractional liquid-liquid extraction process is studied. Based on the numerical results, it is found that the fractional countercurrent multistage liquid-liquid extraction with reflux is superior to the other extraction processes for separating taxane compounds.

Solid-Phase Extraction of Perphenazine from Blood Serum for High Performance Liquid Chromatographic Analysis

A solid-phase extraction (SPE) process has been developed with the aim of replacing multistage liquid-liquid extraction that is currently used for sample clean-up before the chromatographic determination of perphenazine (PPZ) in serum. The method comprises the trapping of PPZ from 2 mL of serum by 100 mg of silica gel with polymeric C18 phase, followed by rinsing of the endogenous compounds with water and acetonitrile. The drug is eluted with 0.7 mL of methanol and the eluate is evaporated to dryness under stream of air. The residue is dissolved in 100 μL of methanol and 20–μ aliquot is injected onto an HPLC column packed with silica gel modified with cyanopropyl groups. To control the retention and separation of PPZ from the other compounds, ammonium acetate concentration in the mobile phase consisting of 90% v/v methanol has been varied from 10 to 40 mmol/L. The SPE method enabled 86.2+5.0% of PPZ to be recovered which is 12% to 22% more than by liquid-liquid extraction procedure. The repeatability of 5.7% (rel.) and the limit of detection (S/N=3) of 1.3 ng/mL have been attained. The method has been verified on serum samples from patients medicated with PPZ.

Advances in Rare Earths Separation and Purification

The conventional method of separation of rare earths by multistage liquid-liquid extraction is still the best processing technology for their separation and purification. One of the most promising developments in the last decade that could have an impact on the rare earths separation technology is the synthesis of mucrocyclic ligands that have a high degree of selectivity in their complexation. Trivalent lanthanides have recently been transported across liquid membranes containing macrocycic ligands. The use of facilitated liquid membranes reactors in the concentration of very dilute rare eaith streams can be very effective in terms of recovery as well as environmental considerations. The electroreduction of E3+ to E2+ and the electroodixation of Ce3+ to Ce4+ are potential replacements for chemical reaction valence change methods. The electrolytic method eliminates the introduction of other chemical reagents that need to be treated downstream to satisfy environmental codes. Improvements in the design and ...

A method of calculating multistage liquid-liquid extraction for ternary systems.

This work has aimed at developing a simple and stable method for the calculation of solvent extraction process with sufficient accuracy for practical application

Preconcentration in multistage liquid-liquid extraction

Theoretical possibilities of the preconcentration of solutes in multistage static liquid-liquid extraction have been investigated. It was found that the preconcentration increases with increasing distribution ratio of the solutes between two phases as well as with the number of stages (n) and reaches its maximum value for n approaching infinity, i.e., in dynamic extraction. Comparison of the preconcentration in multistage (Pns) and one-stage (p1s) static operations shows that the relative preconcentration (qns=pns/p1s) increases to infinity as the separation efficiency approaches 100%. Some of these theoretical considerations have been confirmed in extraction of radioiodine from aqueous solutions.

Control of Mixer-settlers by Decentralized Methods

Abstract The problem of controlling multi-stage liquid-liquid extraction processes is considered. Using linearized dynamic models, it is shown that decentralized control methods can be used to design non-interacting feedback loops. Simulation studies illustrate the potential of the design procedure.