Quantitative Analysis of Cs Extraction by Some Dialkoxycalix[4]Arene-Crown-6 Extractants

Cesium extraction from acidic media by seven dialkoxy-calix[4]arene-crown-6 compounds in several diluents was studied. 2-Nonanone was found to be a suitable diluent for cesium extraction. Nitric acid concentration variation reveals a maximum distribution ratio, whose position depends on extractant and diluent. This maximum was explained quantitatively by a competitive extraction of H⁺. An analytical mass-action extraction model accounting for activity effects is proposed that fits correctly the different datasets. The analysis showed a nitrate hyper-stoichiometry in alkyl ketone diluents. This effect yields efficient back-extraction at low acidity. Benzo substitution on the crown ether lowers nitric acid extraction, improves sodium separation, but also degrades potassium and rubidium separation.     

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.     

Pirouetting in chiral [2]catenanes

One of the best known classes of mechanically interlocked molecules is the category of [ 2 ]catenanes, which exhibit donor-acceptor interactions between the 1,5-dioxynaphthalene (DNP) units in a crown ether and the bipyridinium units in the tetracationic cyclophane, cyclobis(paraquat-p-phenylene) (CBPQT⁴⁺). In order to gain an in-depth understanding and appreciation of the stereochemistry and dynamic behavior of these [ 2 ]catenanes, chiral analogues—having both the DNP ring, which is capable of displaying planar chirality, and the axially chiral binaphthol (BINAP) moiety (as both enantiomers and as the racemic modification), in a crown ether, in addition to the CBPQT⁴⁺ cyclophane—have been synthesized using a template-directed protocol. Dynamic ¹H NMR spectroscopy shows that (i) the presence of immutable axial chirality, arising from the BINAP moiety in the crown ether component, leads to no induction of diastereoselectivity—the chiral catenanes exist as a mixture of diastereoisomers in solution at low temperatures in the approximate ratio of 1:1, (ii) the barrier (ΔG_cD̊) to the interconversion between these two diastereoisomers is 7.9 ± 0.1 kcal mol⁻¹ at 171 K, and (iii) no induction of diastereoselectivity is observed upon the addition of a chiral solvating agent to the chrial catenanes. The pattern of behavior in the variable temperature ¹H NMR spectra and the low ΔTG_cD̊ value indicates that the dynamic process involving the interconversion between these two diastereoisomers is one of a pirouetting nature. Of the four possible diastereoisomers, only two, (R)-(pR/pS) or (S)-(pR/pS), are shown to exist in solution.     

Influence of the Extractant on Strontium Transport from Reprocessing Concentrate Solutions through Flat-Sheet Supported Liquid Membranes

Abstract

The influence of the extractant on strontium transport through a flat-sheetsupported liquid membrane from nuclear fuel reprocessing concentrate solutions to demineralized water has been studied using two crown ethers of different lipophilicity: dicyclohexano-18-crown-6 (DC18C6) and di-tert-butylcyclohexano-18-crown-6 (DtBuC18C6). The distribution coefficients of strontium showed that DC18C6 is a better strontium extractant than DtBuC18C6 in the entire range of crown-ether concentration studied. No effect of association between the DC18C6 molecules was observed even at high concentrations. However, the strong lipophilic character of DtBuC18C6 led to a distribution coefficient of this extractant 10 times higher than the distribution coefficient of DC18C6. Thus, the membrane concentration of DtBuC18C6 was approximately 10 times higher than that of DC18C6. This leads to greater strontium permeability for DtBuC18C6, even though DC18C6 had a greater capacity for strontium extraction and a higher diffusion coefficient in the membrane due to the smaller molar volume of this crown ether. The precipitation of a white solid was observed when the synthetic concentrate was mixed with an organic phase containing DtBuC18C6 dissolved in n-hexylbenzene (0.7 mol·L^?1 isotridecanol), causing a decrease of strontium permeability. In this case, DC18C6 had the greatest strontium permeability.     

Experimental and Simulation on Enantioselective Extraction in Centrifugal Contactor Separators

The increasing demand for optically pure compounds stimulates the development of new chiral separation processes on an industrial scale. The enantioselective liquid–liquid extraction (ELLE) of phenylsuccinic acid (PSA) enantiomers using hydrophilic hydroxyphenyl‐β‐CD as extractant (C) was studied experimentally in a countercurrent cascade of 10 centrifugal contactor separators at 293 K. Based on a single‐stage equilibrium model and the law of conservation of mass, a multistage equilibrium model of ELLE was developed to investigate the influence of changes in the process parameterssuch as phase ratios and concentrations on extraction efficiency. The multistage equilibrium model was verified experimentally with a good agreement. The model was applied to predict the symmetrical separation of PSA enantiomers. By modeling, optimal process parameters for the symmetrical separation of PSA enantiomers can beachieved. The minimum number of stages was determined at 22 and 24 for ee_eq>98% and ee_eq>99%, respectively. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2594–2602, 2013     

In situ polymerization preparation of chiral molecular imprinting polymers monolithic column for amlodipine and its recognition properties study

Amlodipine is a first-line therapeutic drug for hypertension and angina pectoris and its vasodilating effect only resides in the S-(-)-enantiomer. But mostly commercial chiral separating matrixes are not capable of enantio-separating of racemic amlodipine. The amlodipine’s the chiral molecular imprinting polymers monolithic column (CMIPMC) was firstly and successfully synthesized by in situ molecular imprinting technique, utilizing S-(-)-amlodipine as the template molecule, methacrylic acid (MAA) as a monomer, and the resulting monolithic colunm could be directly integrated into the high performance liquid chromatography (HPLC) systems. The scanning electron microscope (SEM) was employed to identify the micro-morphologic features of the obtained polymers. Further, the molecule-special recognition mechanism and special selective absorbent properties for the corresponding template were studied by chromatographic system and Scatchard analysis model, respectively. Meanwhile, the optimized chromatographic conditions for chiral separation of amlodipine enantimoers were established. The results showed the obtained CMIPMC had a high specific affinity and selectivity for the template molecule S-(-)-amlodipine, in which chiral separation of racemic amlodipine was achieved under optimized conditions. The mechanism investigation results showed that two kinds of binding sites prevail in the CMIPMC, besides the molecular shape complementation of template molecular and CMIPMC, hydrogen bond or ionic interaction seem to play an important role in the enantio-selective recognition of the CMIPMC. The research laid fundament for the study of expanding the amlodipine chiral separating medium.     

Modelling and experimental evaluation of reaction kinetics in reactive extraction for chiral separation of amines, amino acids and amino-alcohols

This paper reports on determination of the intrinsic reaction kinetics in reactive extraction of chiral compounds. It is important to know the mass transfer rates and reaction kinetics separately for a reliable scale-up. A kinetic model is developed to interpret the experimental data from the selected model reactor, the modified Lewis cell. The two-phase homogeneous reaction model was selected over the interfacial reaction model, because physical partitioning is considerable in all systems studied. It was shown by simulations and by theoretical considerations that conventional regime analysis fails for reactive extraction in a number of regimes, because the conditions of an irreversible reaction and a negligible resistance to mass transfer in the non-reactive phase are generally not fulfilled in reactive extraction. Furthermore, it follows from the simulations that enhancement of mass transfer by reaction may be partly invisible. Finally, it becomes clear that only the fraction of the species that is in the right ‘extractable’ form should be used in the calculations. As the conventional regime analysis cannot be applied to determine the reaction kinetics in the chiral systems, first the mass transfer rate was measured during physical extraction to determine the location of the main resistance to mass transfer. Then the enhancement of mass transfer was measured during reactive extraction. By model simulation, it was determined how much enhancement of mass transfer should be observable. In this way, it was concluded that the reaction kinetics of the azophenolic crown ether system are between fast and instantaneous, and the reaction kinetics of the Cu(II)-N-dodecyl-L-hydroxyproline system are between slow and fast. The Lewis cell is not the most suitable model contactor to determine reaction kinetics in reactive extraction systems.     

Investigation of liquid–liquid phase equilibria for reactive extraction of lactic acid with organophosphorus solvents

BACKGROUND: Lactic acid is a versatile commodity chemical with a variety of applications. Synthesis of lactic acid either through fermentation of carbohydrates or through chemical synthesis is state of the art. Separation from dilute aqueous solution is complex and accounts for the major part of production costs. Reactive extraction based on reversible adduct formation is a promising alternative for the separation of lactic acid. RESULTS: Extraction was carried out with the organophosphorus solvents tri‐n‐butyl phosphate, tri‐n‐octylphosphine oxide and Cyanex 923. Shellsol T was used as diluent. Partition coefficients increase with increasing extractant content and decreasing temperature. Cyanex 923 has several advantages compared with tri‐n‐butyl phosphate and tri‐n‐octylphosphine oxide with respect to lactic acid distribution and hydrodynamic properties. Liquid‐liquid phase equilibria for lactic acid extraction with Cyanex 923 were modeled. Selectivity of lactic acid extraction with respect to glycolic acid and formic acid was discussed. CONCLUSION: The organophosphorus extractant Cyanex 923 was found to be an appropriate solvent for lactic acid extraction from aqueous solutions. Experimental data and model data based on the Law of Mass Action showed good agreement. Lactic acid extraction from multi‐acid solution showed good selectivity compared with glycolic acid. Lactic acid selectivity is low with respect to formic acid. © 2012 Society of Chemical Industry     

双相（O/W）识别手性萃取分离多巴对映体研究

为了研究多巴在D（L）-2酒石酸异丁酯1,2二氯乙烷有机相和羟丙基-β-环糊精水相萃取体系中的分配行为;运用双相（O/W）识别手性萃取,考察酒石酸构型和浓度、羟丙基-β-环糊精浓度、水相pH值等因素对萃取性能的影响。羟丙基-β-环糊精对S-多巴对映体的识别能力大于对R-多巴对映体的识别能力,而L-酒石酸异丁酯的识别能力刚好相反;在羟丙基-β-环糊精和L-酒石酸异丁酯萃取体系中,多巴外消旋体一次萃取分离后R和S对映体的分配系数（kR和kS）分别为8.92和5.34,分离因子α达1.67;同时pH值和萃取剂浓度对手性分离能力有显著的影响。双相（O/W）识别手性萃取具有较强的手性分离能力,它对外消旋体化合物的制备性分离有着十分重要的意义。     

Continuous and selective separation of EGCG from tea polyphenols by fractional extraction: Experiment and simulation

A new and efficient method was explored to continuously separate (−)-epigallocatechin-3-gallate (EGCG) from tea polyphenols (TPs) by fractional extraction in centrifugal contactor separators (CCSs). The effects of different organic solvents on distribution behavior of monomers of TPs were studied, and two green extraction systems were established without reactive extractant. Based on phase equilibrium and the law of conservation of mass, a fractional extraction model was developed to investigate the influence of the process parameters such as phase ratio and the number of stages on extraction efficiency. By simulation and optimization, optimal parameters can be obtained for the separation of EGCG. EGCG can be separated by batch and continuous separation. Excellent results can be achieved by the two methods with high purity, high yield, and large output. Compared to the batch method, the continuous separation is more suitable for production in an industrial scale due to low-cost and continuous separation. © 2018 American Institute of Chemical Engineers AIChE J, 65: 259–269, 2019     

Enantioseparation of 3-chlorophenylglycine enantiomers using Mandyphos-Pd as chiral extractant

Chiral extractant plays a key role in chiral extraction, and considerable efforts have been undertaken for the development of new and efficient chiral extractants in recent years. This work demonstrated for the first time that chiral ferrocenyl diphosphine ligand(Mandyphos-Pd) had considerable ability to enantioseparate 3-Chlorophenylglycine enantiomers with separation factor(α) of 2.64. Mandyphos-Pd concentration and p H had significant influences on enantioselectivity, while operating temperature showed less influence. The extraction experiments can be performed at room temperature(20 °C) which had the advantage of energy saving. After optimization, the highest performance factor(pf, 0.08376) was obtained at the condition of p H 7.8 and Mandyphos-Pd concentration 1.2 mmol·L~(-1). According to the experimental results, the possible recognition mechanism was discussed.     

Metal extraction of a spiked solid with supercritical carbon dioxide

A mixture of D2EPHA (Di-2-Ethyl Hexyl Phosphoric Acid) and n-hexane is used as the extractant solution to extract cobalt ions from a fireproof board in the environment of supercritical carbon dioxide. It is found that the cobalt on the spiked sample can be totally removed in a pilot unit. The influence of the carbon dioxide flow rate, the flow rate of the extractant solution, the ratio of D2EHPA to hexane in the extractant solution, the temperature and the replacement of hexane by methanol are investigated in this study. Upon extraction, the cobalt complex with D2EHPA is precipitated with the extractant solution in a separation tank through depressurization, and the amount of extracted cobalt in the separation tank is sampled and analyzed by ICP-OES. The accumulation of the removed cobalt along the extraction time is plotted as an extraction curve, and a kinetic model is established to predict the extraction. It is found that the kinetic model reasonably fits the experimental data. From the model, it is concluded that the metal extraction depends on reactivity, that the extent of the extraction is determined by the reversible reaction of the ion-exchange between D2EHPA and the cobalt ions and that the adsorption kinetics of the extractant in the environment of supercritical carbon dioxide may play an important role in the initial stage of extraction. The proposed model, which successfully provides an easy and accurate prediction for metal extraction from a porous solid matrix, can help to reveal the extraction mechanism and optimize the operational conditions for future scale-up designs.     

Pore structure and properties of poly(ether ether ketone) hollow fiber membranes: influence of solvent‐induced crystallization during extraction

Poly(ether ether ketone) (PEEK) hollow fiber membranes were prepared by a thermally induced phase separation method with polyetherimide as diluent, and N‐methyl pyrrolidone (NMP), dichloromethane and a composite extractant composed of NMP, ethanolamine and water as extractant. The effects of the different solvents induced crystallization on the pore structure during extraction and the properties of the PEEK hollow fiber membranes were investigated in detail. The crystallization behaviors of the membranes were characterized by DSC and XRD. The effect of the extractants on the microscopic morphologies, pore structures, water fluxes and mechanical properties of the membranes were investigated. The results showed that the extraction ability of the composite extractant was the most significant, followed by NMP and dichloromethane. The crystallinity of the hollow fiber was 39.0% before extraction and was elevated to 39.2% after the extraction with NMP, 46.6% with dichloromethane and 46.7% with the composite extractant, which shows that dichloromethane and the composite extractant have strong ability to induce the crystallization of PEEK. The inner and outer surfaces of the membranes obtained after extraction by the composite extractant had the largest pore size and the highest surface porosity. The most probable pore diameter of the membranes obtained after extraction by NMP, dichloromethane and the composite extractant was 23.26 nm, 24.43 nm and 24.43 nm, respectively, which indicated that solvent‐induced crystallization was beneficial for the formation of larger pores. The pure water flux of the PEEK membrane prepared by the composite extractant was the largest, but the tensile strength was the lowest. © 2019 Society of Chemical Industry     

氟草烟异辛酯对映体的手性拆分

利用高效液相色谱手性固定相法对氟草烟异辛酯对映异构体进行了拆分研究。使用了正己烷和石油醚两种流动相体系,正己烷流动相条件下考察了多种极性改性剂及其含量,以及温度对手性拆分的影响。实验结果显示,以异丙醇为改性剂,在正己烷体系中的分离效果最好,室温下最大分离因子可达到1．2,温度降低有利于对映体的拆分。石油醚体系的分离效果不佳。     

Enantioseparation with liquid membranes

Chiral resolution of racemic products is a challenging and important task in the pharmaceutical, agrochemical, flavor, polymer and fragrances industries. One of the options for these challenging separations is to use liquid membranes. Although liquid membranes have been known for almost four decades and have been used for optical resolutions, no comprehensive review has been published about the use of this technology for enantioseparations. In this review, the various liquid membrane‐related technologies are described and compared, including bulk liquid membranes, emulsion liquid membranes, micelle‐extraction and micellar enhanced ultrafiltration, as well as supported liquid membranes. Next to technological advances, an overview of recent developments in chiral recognition chemistry in liquid–liquid equilibria is presented. The following extractant classes have recently been reported in conjunction with chiral separation: cyclodextrines, BINOL's, calixarenes, crown ethers, BINAP's, tartaric acids and ionic liquids. The use of two supported (non‐liquid) membranes with an inner loop of extract phase appears to be the most stable liquid membrane configuration, allowing for a large degree of freedom in operational conditions such as solvent to feed ratio. The library of solvents still needs broadening to make the technology more versatile and based on the variety of successes with catalytically active organometallic complexes, development of new chiral selector systems based on asymmetric catalysis literature is suggested for future selector screening studies. © 2017 Society of Chemical Industry     

Synthesis and adsorption properties for metal ions of mesocyclic diamine‐grafted chitosan‐crown ether

A new type of grafted chitosan‐crown ether was synthesized using mesocyclic diamine crown ether as the grafting agent. The C2 amino group in chitosan was protected from the reaction between benzaldehyde and chitosan to form N‐benzylidene chitosan (CTB). After reaction with mesocyclic diamine crown ether of the epoxy propane group to give mesocyclic diamine‐N‐benzalidene chitosan (CTBA), the Schiff base was removed in a dilute ethanol hydrochloride solution to obtain chitosan‐crown ether (CTDA). Its structure was confirmed by FTIR spectra analysis and X‐ray diffraction analysis. Its static adsorption properties for Pb(II), Cu(II), Cd(II), and Cr(III) were studied. The experimental results showed that the grafted chitosan‐crown ether has high selectivity for the adsorption of Cu(II) in the presence of Pb(II), Cu(II), and Cd(II) and its adsorption selectivity is better than that of chitosan. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1255–1260, 2000     

替考拉宁在不同液液萃取体系中分配系数的测定

Teicoplanin is one of the macrocyclic glycopeptide antibiotics, which is active against Gram-positive bacteria, and has attracted a lot of attention in the field of chiral separation recently. In this work, the partition coefficients and extraction ratio of teicoplanin in three different solvent systems were studied: conventional extraction, reactive extraction and reverse micelle extraction. With conventional solvent extraction, n-butanol demonstrated high partition coefficient for teicoplanin, but low extraction ratio because of its high solubility in water. Reactive extraction of teicoplanin showed the highest partition coefficient with almost 100% recovery in organic phase when tri-n-octylmethyl ammonium chloride (TOMAC) was used as extractant and pH value was above 5.0. A reverse micelle system, consisted of isooctane 10 mmol-L^-1 TOMAC -t-1% n-octanol, also offered high separation factor for teicoplanin. The results are beneficial for the design of teicoplanin separation and purification process.     

醋酸正丙酯萃取提纯工艺研究

针对醋酸正丙酯生产过程中分离提纯困难,生产能耗高的现状,研究了由盐类组成复合萃取剂在醋酸正丙酯分离中的应用。该萃取剂在常温下可改变醋酸正丙酯-正丙醇-水体系的互溶度,大幅度提高组分在二相中的分配系数和选择性系数。研究了工艺参数对醋酸正丙酯提纯效果的影响,萃取比为0.8,经三级错流萃取后,有机相中酯的质量分数从93.87%提高到98.44%,比传统工艺可以节能35.2%,萃取剂回收容易,同时能增大原设备的生产能力。     

Determination of Teicoplanin A2's Partition Coefficient in Different Liquid-Liquid Extraction Systems

Teicoplanin is one of the macrocyclic glycopeptide antibiotics, which is active against Gram-positive bacteria, and has attracted a lot of attention in the field of chiral separation recently. In this work, the partition coefficients and extraction ratio of teicoplanin in three different solvent systems were studied: conventional extraction, reactive extraction and reverse micelle extraction. With conventional solvent extraction, n-butanol demonstrated high partition coefficient for teicoplanin, but low extraction ratio because of its high solubility in water. Reactive extraction of teicoplanin showed the highest partition coefficient with almost 100% recovery in organic phase when tri-n-octylmethyl ammonium chloride (TOMAC) was used as extractant and pH value was above 5.0. A reverse micelle system, consisted of isooctane 10mmol-L-1 TOMAC 1% n-octanol, also offered high separation factor for teicoplanin. The results are beneficial for the design of teicoplanin separation and purification process.     

多级离心逆流萃取萘普生对映体模拟及实验研究

基于萘普生(NAP)对映体的单级手性萃取数学模型和质量守恒定律,建立了多级离心逆流萃取萘普生对映体数学模型。采用Matlab语言编写程序模拟了相比、萃取剂浓度、水相pH值等参数对萃取相出口对映体过剩量和产率的影响,并经实验研究对模型模拟进行验证。结果表明:采用中间进料,对映体浓度[R,S-NAP]=0.025 mol·L^-1、萃取剂浓度[C]=0.050 mol·L^-1、相比W/O=7、水相pH=2.5、温度T=5℃时,经10级离心逆流萃取后萃取相出口S-NAP对映体过剩量为45%,相应的产率60%,实验结果和模型模拟值符合得很好。