Calixcrown Ether Research Articles

Comparison of the hydraulic characteristics of the 30%TRPO/kerosene―HNO3 and iPr-C[4]C-6/n-octanol―HNO3 systems in an annular centrifugal extractor

The hydraulic characteristics of the 30% TRPO (trialkylphosphine oxide)/kerosene―1.0 M HNO3 and 0.025 M iPr-C [4]C-6 (25,27-bis(isopropoxy) calix [4]-26,28-crown-6)/n-octanol―1.3 M HNO3 systems were systematically investigated in a φ20 ACE (annular centrifugal extractor) to find the cause of the hydraulic performance problem of the CECE (calixcrown ether extraction) process operated in ACEs. The results show that the operating and structure parameters have different influences on the F (A/O) (phase ratio (A/O)) and V (liquid hold-up volume). Moreover, the Vr (V of the rotor) of the 30%TRPO/kerosene―HNO3 and iPr-C [4]C-6/n-octanol―HNO3 systems are almost same, while the Vm (V of the mixing zone) and Vt (total V of the ACE) for the former are slightly higher than those for the latter under the same experimental conditions. Meanwhile, both the Fm (A/O) (F (A/O) of the mixing zone) and Fs(A/O) (F (A/O) of the separating zone) for the 30%TRPO/kerosene―HNO3 system are also higher than those for the iPr-C [4]C-6/n-octanol―HNO3 system under the same experimental conditions. Moreover, the Fs(A/O) of the iPr-C [4]C-6/n-octanol―HNO3 system is less than 1.5 under most of the present experimental conditions, which shows organic phase entrainment may easily occur in the outlet aqueous phase. This may be the cause of the hydraulic performance problem of the CECE process operated in ACEs.

Experimental and theoretical insight into the extraction mechanism, kinetics, thermodynamics, complexation and radiolytic stability of novel calix crown ether in ionic liquid with Sr2+

A comparative evaluation was carried out for the extraction of Sr2+ using novel calix crown ether in molecular diluent and in ionic liquid. Though the trend in extraction profiles was found to be similar for both the systems, still, almost 5 times higher distribution ratio (D) values were observed in ionic liquid. The speciation studies revealed that; neutral Sr (NO3)2. DHCC species was formed in dodecane and the extraction followed through ‘solvation’ mechanism. However, ionic liquid medium (IL), anionic species, [Sr(NO3)3. DHCC]− was found to be predominating indicating ‘anion exchange’ mechanism. The slower kinetics of extraction in IL was attributed to the high viscosity of IL. The extraction process was found to be spontaneous, endothermic and entropy driven.IL based system was found to be radiolytically more stable compared to the molecular diluent (Mol dil) based system. The electron paramagnetic resonance (EPR) spectroscopic investigation revealed the formation of oxygen centered radical with orthorhombic symmetry (gx = 2.00105, gy = 2.00475, gz = 2.00835) in irradiated ligand. The density functional theoretical (DFT) calculation was utilized to investigate the complexation and speciation in detail in microscopic level.

Diluents induced tuning of the extraction characteristics of radioactive Cs from acidic nuclear waste solution using calix crown ether

The present investigation deals with understanding the effect of different diluents on the extraction properties of Cs+ using novel calix crown ether. The extraction efficiency was found follow the same order as the dielectric constant of the diluents. The extraction mechanism and the species involved during extraction were evaluated. The extraction process was found to be fast. Suitable stripping procedure was also optimized using different aqueous complexing agents. The effect of radiation exposure on the performance of these solvent systems in extraction of Cs+ ion was investigated up to 1000 kGy. The performance of octanol and isodecyl alcohol was found to be optimized with respect to radioactive plant scale operations.

Hydraulic characteristics of n-octanol/aqueous solution systems in a 25-mm annular centrifugal extractor

ABSTRACTThe hydraulic characteristics of the n-octanol/H2O, n-octanol/1 M HNO3 solution, and kerosene/H2O systems in the 25-mm annular centrifugal extractor (ACE) were investigated to provide guidance for optimizing the operation parameters and heavy phase weir diameter of the 25-mm ACEs used in a production line to extract 137Cs and 90Sr using the calixcrown ether cesium extraction (CECE) and crown ether strontium extraction (CESE) processes, respectively, from high-level liquid waste (HLLW). The effects of the flow ratio (A/O), rotor speed, and heavy phase weir diameter on the hydraulic characteristics of n-octanol/aqueous solution systems in the 25-mm ACE are complex. Moreover, the hydraulic characteristics of n-octanol/aqueous solution systems are very different from those of the kerosene/H2O system in the 25-mm ACE. All results showed when the 25-mm ACEs will be used in the CECE and CESE processes, the heavy phase weir diameter and rotor speed should correspond to ranges of 12.5 to 13.0 mm and 3000 to 3500 r/min, respectively, to meet the requirement the total flow rate of 3 L/h in the production line for the recovery of 137Cs and 90Sr.

Cesium liquid-liquid extraction by calix-crown ethers: solvent effect

Cesium liquid-liquid extraction by calix-crown ethers: solvent effect

Demonstration of an Improved Total Partitioning Process for High Level Liquid Waste Using Annular Centrifugal Contactors

High level liquid waste (HLLW) produced from the reprocessing of the spent nuclear fuel still contains moderate amounts of uranium, transuranium (TRU) actinides, 90Sr, 137Cs, etc., and thus constitutes a permanent hazard to the environment. The partitioning and transmutation (P&T) strategy has increasingly attracted interest for the safe treatment and disposal of HLLW, in which the partitioning of HLLW is one of the critical technical issues. An improved total partitioning process, including a TRPO (tri-alkylphosphine oxide) process for the removal of actinides, a CESE (crown ether strontium extraction) process for the removal of Sr, and a calixcrown ether extraction process for the removal of Cs, has been developed to treat Chinese HLLW at the Institute of Nuclear and New Energy Technology (INET), Tsinghua University, China. A demonstration test of the improved total partitioning process was carried out using 74-stage 10-mm-dia annular centrifugal contactors and simulated HLLW. The test results showed that the decontamination factors were >1.2 × 106, 4600, and 7500 for Nd, Sr, and Cs, respectively. In the test, Nd was used to simulate Am. During the test, 74-stage 10-mm-dia annular centrifugal contactors worked stable continuously with no stage failing or interruption of the operation.

Application of annular centrifugal contactors in the hot test of the improved total partitioning process for high level liquid waste

High level liquid waste (HLLW) produced from the reprocessing of the spent nuclear fuel still contains moderate amounts of uranium, transuranium (TRU) actinides, 90Sr, 137Cs, etc., and thus constitutes a permanent hazard to the environment. The partitioning and transmutation (P&T) strategy has increasingly attracted interest for the safe treatment and disposal of HLLW, in which the partitioning of HLLW is one of the critical technical issues. An improved total partitioning process, including a TRPO (tri-alkylphosphine oxide) process for the removal of actinides, a CESE (crown ether strontium extraction) process for the removal of Sr, and a CECE (calixcrown ether cesium extraction) process for the removal of Cs, has been developed to treat Chinese HLLW. A 160-hour hot test of the improved total partitioning process was carried out using 72-stage 10-mm-dia annular centrifugal contactors (ACCs) and genuine HLLW. The hot test results showed that the average DFs of total α activity, Sr and Cs were 3.57×103, 2.25×104 and 1.68×104 after the hot test reached equilibrium, respectively. During the hot test, 72-stage 10-mm-dia ACCs worked stable, continuously with no stage failing or interruption of the operation.

Thiacalix-monocrown ethers with terminal functional groups at the lower rim: Synthesis and structure

170 Nowadays, one of the intensively developed areas in organic chemistry focuses on design, synthesis, and studying the properties of nanoscale molecular sys tems containing several structural blocks capable of fulfilling different functions, for example, receptor and sensor functions. Such molecules can serve the basis for design of “smart” materials in various areas of nanoengineering and materials science. The most effi cient strategy of obtaining such nanosystems involves combination of appropriate structural fragments. In particular, combination of a calixarene and crown ether moieties in one molecule led to the appearance of a new class of receptors, calix crown ethers 1a, which exhibit extremely high alkali metal ion bind ing selectivities [1–9]. Polyether bridged calix[4]arenes 1b [1, 2] exhibit a high Cs+/Na+ selectivity (more than 30 000) in solution. They are widely used as iono phores and carriers in liquid membranes [3, 4]. However, no attempts to fix them onto a solid sub strate for creating ion selective electrodes and sen sors have been described so far, since no efficient ways of synthesis have been developed for calix crown ethers in which the acyclic substituent R contains functional groups capable of fixing the molecule onto a solid surface and forming regularly arranged nanolayers and films. In this context, it is of definite interest to introduce thiol groups into such structures, since they can be efficiently fixed on the gold and silver surface [10]. CHEMISTRY

Efficient removal of caesium ions from aqueous solution using a calix crown ether in ionic liquids: mechanism and radiation effect

The removal of radioactive (137)Cs from nuclear waste is of great importance for both the environment and energy saving. Herein, we report a study on the removal of Cs(+) using a calix crown ether bis(2-propyloxy)calix[4]crown-6 (BPC6) in ionic liquids [C(n)mim][NTf(2)], where [C(n)mim](+) is 1-alkyl-3-methylimidazolium and [NTf(2)](-) is bis(trifluoromethylsulfonyl)imide. The BPC6/[C(n)mim][NTf(2)] system is highly efficient in removing Cs(+) from aqueous solution, even at a low concentration of BPC6. HNO(3) and metal ions such as Na(+), Al(3+) in the aqueous phase interfered with the extraction of Cs(+) by competitive interaction with BPC6 and/or salting-out effect. UV analysis confirmed that the extraction of Cs(+) by the BPC6/[C(n)mim][NTf(2)] system involves a dual extraction mechanism, i.e., via exchange of BPC6.Cs(+) complex or Cs(+) by [C(n)mim](+). Irradiation of [C(4)mim][NTf(2)] dramatically decreases Cs(+) partitioning in the ionic liquid phase by the competitive interaction of radiation-generated H(+) with BPC6, while irradiation of BPC6/[C(4)mim][NTf(2)] decreases Cs(+) partitioning more markedly due to the radiolysis of BPC6.

Macrocycle carriers for separation of metal ions in liquid membrane processes—a review

A review with more than 60 references covering macrocycle and macromolecular compounds, i.e. crown ethers, ionizable lariat ethers, calixarenes, calix crowns, as well as macrocycle polymers (for example, cyclodextrins), and macromolecular compounds, i.e. acyclic polyethers used as ion carriers in transport across liquid membranes for metal ions selective removal will be presented. The recent literature data as well as our own research results (published in the last 8 years) on metal ions removal and separation will be summarized. Recent developments of the lariat ethers application as ion carriers for alkali metal and alkaline earth metal cations, as well as heavy metal ions removal and separation will be presented in this review. The effect of structural studies of crown ring size variation, lipophilic and acidic group attachments for lariat ethers with carboxylic and other acidic groups on the selectivity and efficiency of metal cations transport will also be presented. Also, the effect of a counter anion presence will be performed. The examples of metal ions selective removal using various other ion carriers such as calixarenes, calixcrown ethers, cyclodextrins and their polymers as well as acyclic polyethers will also be shown.

New Fluorescent Calix Crown Ethers, Part II: Synthesis and Complex Formation in Solution and the Solid State

AbstractNew luminescent 1‐aza‐15‐crown‐5 ethers bearing a coumarin unit were synthesised leading to the cavitand‐based calix crown ether 9. The solid‐state structures of crown ethers 5 and 6 and the solid‐state structures of the sodium and potassium iodide complexes of crown ether 5 are presented. The association constants for the complex formation with alkali metal ions in methanol were determined. Only weak complexes were formed (KNa = 286 M–1, KK = 392 M–1). The aza‐15‐crown‐5 ether was attached by a methylene unit to a cavitand to give the new fluorescent calix crown ether 9. The association constants for the sodium and potassium complexes in methanol were investigated as well, and an enhancement for the association constant of the sodium complex was found (KNa = 1215 M–1, KK = 497 M–1). Selected equilibrium structures of the complexes of 9 were examined by Kohn–Sham density functional calculations to give a detailed understanding of the interplay between the two involved building blocks. Based on these results, a sidewise cation binding of the host 9 can be assumed. These complex geometries are distinct from our findings in our previous work for a larger crown ether attached to a cavitand.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

A New Fluorescent Calix Crown Ether: Synthesis and Complex Formation with Alkali Metal Ions

We synthesised a new N-benzylaza-21-crown-7 ether 5 with a dihydroxy coumarin as a fluorescence sensor and investigated the binding behaviour towards alkali metal cations in methanol by fluorescence titrations. The association constants are within one order of magnitude, with the exception of sodium. Potassium is the preferred binding partner (K(Na)=330 M(-1); K(K)=8600 M(-1); K(Rb)=8200 M(-1); K(Cs)=4400 M(-1)). The corresponding aza-21-crown-7 ether (6) was attached by a methylene unit to a resorcarene to give fluorescent calix crown ether 12. The binding abilities of the calix crown ether towards alkali metal ions in methanol have also been investigated, and an increasing complex stability, distinct for potassium and rubidium in comparison with 5, was found: K(Na)=440 M(-1); K(K)=110,000 M(-1); K(Rb)=63,000 M(-1); K(Cs)=20,000 M(-1). Like bis(crown ether)s, a cooperative complexation of the crown ether and the cavitand scaffold can be assumed. The proposed complex geometry is supported by Kohn-Sham DFT calculations for the potassium and caesium complexes.

Chromoionophoric Recognition of Alkylamines by Nitro Derivative of Calix[4]arene-crown-5 Ether

Department of Chemistry, Chung-Ang University, Seoul 156-756, KoreaReceived December 4, 2003Key Words : Calix-crown ether, Alkylamine, Chromoionophore, OR logic gate The molecular design of efficient and selective chromo-genic and fluorogenic ionophore systems for the sensing ofchemically and biologically important ionic guests hasattracted much attention in the past decade.

Analytical Potentialities of Calix-Crown Ethers

Analytical Potentialities of Calix-Crown Ethers

A solution to stripping problems caused by organophilic anion impurities in crown-ether-based solvent extraction systems: a case study of cesium removal from radioactive wastes

A problem related to stripping efficiency has been identified in the use of crown ether derivatives to extract alkali metal salts, and a simple solution is proposed. Focusing on the specific case of cesium extraction from simulants of alkaline nuclear waste by a calix-crown ether, calix[4]arene-bis( tert-octylbenzo-crown-6) (BOBCalixC6), it has been shown that low concentrations of a common surfactant, dodecylsulfonate, seriously impairs stripping. This surfactant has been identified as a trace component in laboratory simulants and was subsequently studied in experiments in which it was added in controlled amounts. Computer modeling of stripping behavior is consistent with the formation of a 1:1:1 organic-phase complex of the calix-crown with cesium and its nitrate counterion. In the presence of an organophilic surfactant anion, cesium ion can only effectively be stripped from the solvent until its organic-phase concentration becomes equivalent to that of the surfactant anion. Cleanup of nuclear waste requires a high decontamination factor for 137Cs, and insufficient stripping therefore leads to process failure. This difficulty raises a generic issue for use of crown ethers for waste decontamination or for other hydrometallurgical applications. However, remediation is possible by simply adding an alkylamine to the solvent. The alkylamine in its ammonium form acts as a counterion of the organophilic anion, suppressing the deleterious effects of the organophilic anion and allowing the cesium cation to be stripped efficiently. Trioctylamine (TOA) at a concentration of only 1 mM was found effective at restoring stripping performance while not affecting extraction. Ultimately, this solvent amendment enabled the development of a robust solvent for the Caustic-Side Solvent Extraction (CSSX) process and its successful demonstration on actual nuclear waste.

Calixcrown oligomers as cation carriers in a bulk liquid membrane

One monomeric calixcrown ( 1) and four calixcrown oligomers ( 2– 5) were used as carriers in a bulk liquid membrane. All the carriers transported K + selectively, the order of the transport rate being: the calixcrown amide oligomer 4>the calixcrown ether oligomer 2>the calixcrown ester oligomer 3>the calixcrown siloxane oligomer 5, and the K +/Na + selectivity decreased in the reverse order. These results demonstrate that the transport rate and the selectivity of calixcrown oligomers are related to the type of second component linking the calixcrown unit. In two-cation transport experiments, at high [K +]/[Na +] ratios, all the carriers transported K + over Na +. As the ratio decreased, the transport of Na + becomes favored, indicating that the cation flux depends, in part, on the relative concentrations of the cations in the source. Under our experimental conditions, the transport rate of Na + remains almost unchanged with a constant concentration of Na + and various concentration of K +.

Selective transport of cesium ion in polymeric CTA membrane containing calixcrown ethers

A series of calixcrown ethers for which the cavity size of the crown ring is varied from crown-6 to crown-7 to crown-8 were examined for the transport abilities toward alkali metal ions. These ligands were incorporated into supported liquid membranes (SLMs) and into polymer inclusion membranes (PIMs) composed of cellulose triacetate (CTA) as a support and 2-nitrophenyl octyl ether (NPOE) and tris(2-butoxyethyl) phosphate (TBEP) as a plasticizer. In both membrane systems, calixcrown-6 showed the best selectivity toward a cesium ion over other alkali metal ions. The polymeric CTA membrane showed more rapid transport rate as well as higher durability than did the SLMs.

Calix[4]arenes Bridged with Two Different Crown Ether Loops: Influence of Crown Size on Metal Ion Recognition

A series of calix[4]arene-bis-crownethers were synthesized in a fixed 1,3-alternateconformation with good yields by the reaction of amonocyclic calixcrown ether with multi-ethyleneglycoldi-p-toluenesulfonate in the presence of cesiumcarbonate. In the preparation of the monocycliccalixcrown ethers (1 and 2), the use ofpotassium carbonate as a base provided the best yieldregardless of the template concept. In two phaseextraction and competitive transport experiments forligand-metal complexation, calix[4]arene biscrown(5) provided the best selectivity for potassiumion. When a calixbiscrown ether (4) bearingdifferent sized crown ether loops coordinates to K+and Cs+, respectively, the changes of peak splittingpatterns and chemical shift on 1H NMR spectra aredependent on the complexed metal ion species.

New Calix[4]arene Dibenzocrown Ethers for Selective Sensing of Cesium Ion in an Aqueous Environment

1,3-Dialkoxycalix[4]arene dibenzocrown ethers (6, 7, 8, 9) were successfully synthesized in the fixed 1,3-alternate conformation, with greater than 90% yields by reaction of the corresponding 1,3-dialkoxycalix[4]arenes 2–5 with dibenzodimesylate 13 in acetonitrile as a solvent in the presence of cesium carbonate as a base. In view of the cyclization yield, dimesylate is better than dibenzoditosylate. Because of an unusualABpattern in the1H NMR spectrum for compound 9, it is suggested that the conformational structure of 1,3-diallyloxy calix[4]arene dibenzocrown ether is less flexible than that of usual 1,3-alternate calixcrown ether, probably due to steric effects of two allyl groups. Complexation of the corresponding calix[4]arene ethers 6–9 to alkali metal ions using the single-flux method through a bulk liquid membrane system was found to give high cesium selectivity.

Synthesis of supramolecular structures via combination of calix[4]arenes with other medium-sized building blocks

Abstract