EXTRACTION OF CESIUM NITRATE FROM CONCENTRATED SODIUM NITRATE SOLUTIONS WITH 21-CROWN-7 ETHERS: SELECnVITY AND EQUILIBRIUM MODELING

ABSTRACT

The extraction of cesium nitrate from a high concentration of sodium nitrate by a family of 21-crown-7 ethers in 1,2-dichloroethane has been investigated. Dibenzo-21-crown-7 (DB21C7) and bis[4(5),4′(5′)-rm-butylbenzo]-21-crown-7 (BtBB21C7) ethers have higher selectivity for cesium but lower extraction efficiency than dicyclohexano-21-crown-7 (DC21C7) ether. As measured by the distribution coefficient ratio D_cs/D_Na, the cesium selectivity averaged 78 and 93 for DB21C7 and BtBB21C7, respectively. However, in the case of DC21C7, the cesium selectivity was lower and decreased approximately three-fold from 10 to 3 as cesiüm loading increased. Alkyl substitution on the benzo group has only a small effect on the extraction behavior. It was shown by use of the equilibrium modeling program SXLSQI that the extraction of sodium and cesium could be adequately modeled by augmenting the previously determined cesium nitrate equilibrium model with a 1:1 Na⁺:crown organic-phase complex. No evidence for a mixed-metal species was found. In accord with our previous study, cesium nitrate extraction entails formation of a 1:1 Cs⁺:crown complex, but a minor 1:2 complex also forms in the case of DC21C7. Although the sodium and cesium made possible by the U. S. Department of Energy Postgraduate Research Program administered by the Oak Ridge Associated Universities.     

RADIUM SEPARATION THROUGH COMPLEXATION BY AQUEOUS CROWN ETHERS AND ION EXCHANGE OR SOLVENT EXTRACTION

ABSTRACT

The effect of three water-soluble, unsubstituted crown ethers (15-crown-5 (15C5), 18-crown-6 (18C6) and 21-erown-7 (21C7) on the uptake of Ca, Sr, Ba and Ra cations by a sulfonic acid cation exchange resin, and on the extraction of the same cations by xylene solutions of dinonylnaphthalenesulfonic acid (HDNNS) from aqueous hydrochloric acid solutions has been investigated. The crown ethers enhance the sorption of the larger cations by the ion exchange resin, thereby improving the resin selectivity over calcium, a result of a synergistic interaction between the crown ether and the ionic functional groups of the resin. Similarly, the extraction of the larger alkaline earth cations into. xylene by HDNNS is strongly synergized by the presence of the crown ethers in the aqueous phase. Promising results for intra-Group IIa cation separations have been obtained using each of the three crown ethers as the aqueous ligands and the sulfonic acid cation exchange resin. Even greater separation factors for the radium - calcium couple have been measured with the crown-ethers and HDNNS solutions in the solvent extraction mode. The application of the uptake and extraction results to the development of radium separation schemes it discussed and a possible flowchart for the determination of ²²⁶Ra/²²⁸Ra in natural waters is presented.

     

Ion-Pair Extraction of Alkali Mental Nitrate Salts by Lipophilic,Benzo-Substituted 24-Crown-8 Ethers

Abstract

The extraction of alkali metal nitrate salts by 24-crown-8 ethers bearing multiple benzo substituents has been surveyed in 1,2-dichloroethane diluent at 25 °C. The results reveal that the addition of benzo-substituents onto the 24-crown-8 increases both the extraction efficiency and the selectivity for the larger cations. Substitution of branched alkyl groups onto the benzo rings of 24-crown-8 ethers has a relatively small influence on their extraction properties.     

Studies of the Size-Selective Extraction of Alkali Metal Ions by the Synergistic Extraction System,Crown Ether-DI(2-Ethylhexyl) Phosphoric Acid-Benzene

Abstract

In order to take practical advantage of the size-selective cation-coordinating ability of the cyclic polyethers (crown ethers), experiments seeking a means of avoiding the problem of solubilizing a mineral-acid anion in a nonpolar organic diluent were performed. Mixtures of several known extractants and crown ethers were tried. Results presented indicate that organic soluble cation exchangers mixed in solution with crown ethers produce a synergistic extractant mixture that largely exhibits the size-selective properties expected of the crown ether. Data are presented for the extraction of macro concentrations of alkali metals by di(2-ethylhexyl) phosphoric acid—dicyclohexyl-18-crown-6 mixtures at a single pH, and at nonloading condition(σ metal cone < 0.04 M) as a function of pH, 2 to 6. In both cases potassium is synergized most strongly presumably because of its best fit to the crown ether cavity. Other data indicate, however, that the size-fit principle is not as consistent for all alkali metal ions and crown ethers as for potassium and dicyclohexyl-18-crown-6. Other effects such as competition for ion hydration and aqueous-phase distribution of the complex may have important effects that have not been elucidated.     

The Synerqistic Solvent Extraction of Manganese by Macrocyclic Crown Ethers in Combination with Didodecylnaphthalene Sulfonic Acid: Effect of Macrocycle Substituents

Abstract

Crown ethers in combination with organophilic cation exchangers synergize the extraction of certain metai ions from aqueous solutions, and their selectivity has been thought largely dependent on the correspondence between the crown other's cavity diameter and the metal ion diameter. This work focuses on two crown ethers, tert. -butylbenzo -15-crown-5 (tBB15C5). and tert, -butylcyclohexano 15-crown-5 (tBC15C5) each of which has a cavity diameter of 1.7 to 2.2 × 10^?10 m. and their extraction of Mn²⁺ (ionic diameter 1.4 to 2.2 × 10^?10 m) from aqueous nitrate solutions. The organophilic cation exchanger used was didodecylnaphthalene sulfonic acid (HDDNS). The data show no observable complexes of the manganese salt of HDDNS     

SURVEYING THE EXTRACTION OF CESIUM NITRATE BY 1,3-ALTERNATECALIX[4]ARENE CROWN-6 ETHERS IN 1,2-DICHLOROETHANE

ABSTRACT

The extraction of cesium nitrate from a mixture of alkali metal nitrates by calix7lsqb;4]arene crown-6 ethers in 1,2-dichloroethane diluent has been surveyed at 25 °C. The results reveal that smaller substituents (but larger than C₂,) at the phenolic positions of the calixarene opposite the crown ether increase both the extraction efficiency and the cesium selectivity. Benzo substituents on the crown ether tend to decrease extraction strength while increasing cesium-to-sodium selectivity. Conversely, a cyclohexano group on the crown ether has a negative impact on both extraction strength and selectivity.     

Silver complexes with large crown ethers in propylene carbonate

The complex formation between large crown ethers – e.g. dibenzo-30-crown-10 – and Ag⁺ in propylene carbonate has been studied using potentiometric and calorimetric titrations. The values of the reaction enthalpies with larger crown ethers than 18-crown-6 especially with dibenzo-30-crown-10 indicate that more than six donor atoms are taking part in the interaction with the complexed cation. The values of the reaction entropies of the largest crown ethers examined indicate the high sterical requirements of the complex formation. Obviously large crown ethers are able to encapsulate the complexed cation. The effectiveness of the encapsulation however depends upon the ring size and flexibility of the crown ethers.     

硅杂原子提升冠醚对锂离子络合能力的机理理论研究

将Si引入冠醚有希望大幅度提升其对阳离子的络合能力,但其中的调控机理尚不清晰。基于量子化学密度泛函理论计算,以12-冠-4、1,1-2甲基-1-硅杂12-冠-4、1,1,2,2-4甲基-1,2-2硅杂12-冠-4、1,1,2,2,4,4,5,5-8甲基-1,2,4,5-4硅杂12-冠-4和1,1,2,2,7,7,8,8-8甲基-1,2,7,8-4硅杂12-冠-4络合Li⁺为计算模型,探究了冠醚与Li⁺之间的相互作用机理。结果表明,由于O—Li⁺配位键的键长增加,掺杂Si的数量为2和4的Si杂12-冠-4对Li⁺的共价相互作用略弱,但静电相互作用和色散相互作用更强、Pauli排斥作用更小,最终导致所有Si杂12-冠-4对Li⁺的络合能力都比12-冠-4更强。上述有利因素源于Si—O键中Si的电子显著向O极化,同时,Si杂12-冠-4中—SiMe₂—SiMe₂—和—CH₂—SiMe₂—单元远离Li⁺,有效避免了Si—Li⁺之间的静电排斥。揭示的冠醚-Li⁺相互作用机理将为未来设计与合成杂原子冠醚提供理论指导。     

EXTRACTION SYSTEMS USING BIS-1,2-0ICARBCILYLC0BALTATE ANO POLYOXONIUM COMPOUNDS FOR LANTHANIOE SEPARATIONS

ABSTRACT

The extraction of rare earths (lanthanides, Y, Sc) by voluminous bis-1,2-dicarbollylcobaltate anions disolved in nitrobenzene and in a nitrobenzene - carbon tetrachloride mixture has been investigated and the exchange extraction constants for both solvents, individual extraction constants anddG for ion transfer across the water - nitrobenzene phase boundary has been determined. Extraction decreases with increasing atomic number of the lanthanide.

The influence of several polyoxonium compounds on the distribution ratios and the extraction selectivity has been investigated. In the extraction systems with bis-1,2-dicarbollylcobaltate - 18-crown-6 in nitrobenzene, synergism was found for the light lanthanides but antagonism was observed for the heavy ones. The overall separation factor is Ctla/10 compared to in the absence of crown la/²     

Spacer-chromoionophores — polymethine dye substituted aza-crown ethers with increased complexation ability

Aromatic aldehyde derivatives of N-phenyl-aza-15-crown-5 ( 2 ), N-phenyl-aza-18-crown-6 ( 8 ), and benzo-15-crown-5 ( 10 ) are condensed with malononitrile and 2-amino-1,1,3-tricyano-1-propene to give light yellow to orange colored crown ether derivatives 4 , 5a , 9a , 11 , and 12 . 5a and 9a were acylated with ethyl chloroformate to give the magenta colored dyes 5b and 9b , respectively. By condensation of N-(4-nitrosophenyl)-aza-15-crown-5 3 with 2-amino-1,1,3-tricyano-1-propene the magenta dye 6a is obtained. Acylation of 6a with ethyl chloroformate leads to the deep blue colored dye 6b . In these derivatives the nitrogen or oxygen atoms of the crown ethers are part of the chromophoric system, and binding properties are affected. Further chromophoric derivatives of aza-crown ethers are studied in which these are separated from the chromophoric moiety by a spacer. N-(ω-chloroalkyl)-N-alkylanilines 14a-c were attached to aza-15-crown-5 13a-c and aza-18-crown-6 13b-c to yield the spacer crown ether derivatives 15a-c and 16a-c , respectively. The formylated spacer crown ether derivatives 17a-c and 18b were condensed with 2-amino-1,1,3-tricyano-1-propene to give the orange spacer-chromoionophores 19a-c and 20 . In these crown ether derivatives the extended conjugation is interrupted by the spacer, and good binding properties are obtained. The complex formation constants of the crown ether derivatives with Na⁺ and K⁺ are determined using ¹H NMR spectroscopy.     

Synergistic Enhancement and Separation of Zirconium(IV) and Hafnium(IV) with 3-Phenyl-4-Benzoyl-5-Isoxazolone in the Presence of Crown Ethers

Abstract

3-Phenyl-4-benzoyl-5-isoxazolone (HPBI) was synthesized and examined with regard to the synergistic solvent extraction behavior of zirconium(IV) and hafnium(IV) in the presence of various crown ethers (CEs), namely, 18-crown-6 (18C6), dicylohexano-18-crown-6 (DC18C6) and benzo-15-crown-5 (B15C5) from hydrochloric acid solutions. The results demonstrated that zirconium(IV) and hafnium(IV) were synergistically extracted into chloroform with mixtures of HPBI and CEs as ZrO(PBI)₂ · CE and HfO(PBI)₂ · CE, respectively. The complexation strength follows the order DC18C6 >18C6 > B15C5. The addition of CEs not only enhances the extraction efficiency of zirconium(IV) and hafnium(IV) but also significantly, especially in the presence of B15C5, improves the selectivity (Zr/Hf = 4.73) between these metal ions as compared to HPBI alone (Zr/Hf = 2.09). On the other hand, selectivity has been moderately decreased by the addition of 18C6 or DC18C6 to the metal-chelate system.     

Oxidative desulfurization of diesel fuels in the presence of crown ethers and transition metal peroxo complexes

The catalytic activity of crown ethers and their complexes with transition metal cations in diesel fuel desulfurization has been investigated. With dibenzo-18-crown-6 in combination with NbCl₅, the total sulfur content of the fuel can be reduced by a factor of 2 or larger. The effects of the reaction temperature, nature of metal and crown ether, and sorbent acidity on the residual sulfur content are reported. Methods of separation of oxidized compounds, namely adsorption chromatography and extraction are compared in terms of desulfurization efficiency. The latter method is demonstrated to be preferable.     

Extractive Separation of Lithium Isotopes by Crown Ethers

Abstract

Separative abilities of crown ethers to lithium isotopes were investigated for the number of oxygen atoms composing crown rings and for the substituted groups to 15-crown-5. The separation factors at 0°C were 1.057 for 12-crown-4, 1.042 for benzo-15-crown-5, 1.041 for lauryloxymethyl-15-crown-5, 1.043 for tolyloxymethyl-15-crown-5, and 1.024 for dicyclohexano-18-crown-6. The enthalpy change of the isotopic equilibrium in the absolute value was the greatest for 12-crown-4; ΔH° = ?0.78 kJ/mol. In the substituted 15-crown-5s the separation factor was greatest for tolyloxymethyl-15-crown-5, and ΔH° values decreased in the order: benzo- > tolyloxymethyl- > lauryloxymethyl-15-crown-5. For enthalpy changes, benzo-15-crown-5 has the possibility of giving a larger separation factor than the present one, α = 1.042, by choosing more suitable conditions. In spite of its large distribution coefficient, dicyclohexano-18-crown-6 is not superior for isotopic separation of lithium in regard to the small enthalpy change of isotopic equilibrium; ΔH° = ?0.15 kJ/mol. The addition of DMSO to the initial solution of LiI caused a remarkable increase in the distribution coefficient without changing the isotopic separation factors.     

NUCLEAR SIZE AND SHAPE EFFECTS IN CHEMICAL ISOTOPE ENRICHMENT OF NEODYMIUM USING A CROWN ETHER

ABSTRACT

Neodymium was extracted and isotopically fractionated in the liquid-liquid extraction using a crown ether of dicyclohexano-18-crown-6. The maximum value in isotope enrichment factor was observed on the isotope pair ¹⁴²Nd-₁₅₀Nd, and was ε_142,150 = 0.00084±0.00009: this was 0.00011±0,00001 in terms of the unit mass enrichment factor The isotope enrichment factors showed breakdown of the conventional mass-dependent theory. We presented the advanced theory by use of the nuclear size and shape effect and the nuclear spin effect. The field shift effect was proved to give larger contribution than the nuclear mass effect. The predominance of the field shift effect in this study agreed with our previous studies on samarium and gadolinium.     

LUMINESCENCE STUDY OF Eu( III) COMPLEXES EXTRACTED IN THE ORGANIC PHASE

Luminescence lifetimes have been measured for Eu(III) extracted into benzene solutions. The extrac-tants were HDEHP, HTTA, and mixtures of HTTA with crown ethers, TBP, and TOPO. The results were consistent with no residual hydration for Eu(DEHP)₃, and three molecules of hydration for Eu(TTA) ₃,. The Eu(TTA) ₃,-(TOPO)? _n (n = 1,2) complexes have one water molecule or less. The hydration numbers from the luminescence lifetimes compare well with the values from Karl Fischer titrations. The hydration of the crown ether complexes can be related to the degree of steric hindrance by the aliphatic or aromatic groups attached to the crown ethers.     

Effect of Ring-Size Variation within Dibenzocrown Ether Resins upon Ion-Pair Sorption of Alkali-Metal Cations from Aqueous and Aqueous Methanol Solutions

Abstract

A batch analysis method has been developed for evaluation of metal salt sorption by crown ether polymers. Selectivity in competitive alkali-metal chloride sorption by a series of formaldehyde condensation polymers of dibenzocrown ethers is influenced by the relationship between the crown ether cavity size and metal ion diameter, as well as the degree of hydration of the metal salt. Effective and selective sorption of KCl from the other alkali-metal chlorides was obtained with a dibenzo-18-crown-6 resin. Excellent sorption selectivity for the monovalent metal chlorides was noted for competitive ion-pair sorption of NaCl, KCl, MgCl₂, and CaCl₂ by this resin. This resin was examined as a stationary phase for selective column separation of KCl from alkali-metal chlorides and of KCl and NaCl from alkali-metal and alkaline-earth chloride mixtures in 80% methanol—20% water.     

SMALL ANGLE NEUTRON SCATTERING INVESTIGATION OF THE SPECIES FORMED IN THE EXTRACTION OF Sr(II) BY MIXTURES OF DI-n-OCTYLPHOSPHORIC ACID AND DICYCLOHEXANO-18-CROWN-6

ABSTRACT

Deuterated toluene solutions of di-n-octylphosphoric acid, HDOP, containing Sr⁺ extracted from 0.1 M LiNO₃ aqueous solutions, were investigated by small angle neutron scattering (SANS). The extractions were also performed in the presence of either the cis-syn-cis or the cis-anti-cis stereoisomer of dicyclohexano-18-crown-6 (DCH18C6) in combination with HDOP in the toluene phase. The addition of the crown ether increased metal extraction into the organic phase over that observed with HDOP alone (synergistic extraction), The cis-syn-cis isomer was more effective than the cis-anti-cis isomer in enhancing Sr(II) extraction in the synergistic system. The SANS results confirmed that when the metal cation is extracted by HDOP present in large stoichiometric excess, the predominant species formed in the organic phase can be described as Sr(H(DOP)₂)₂ with 2 extra HDOP molecules solvating the complex. In the synergistic crown ether-HDOP system, the SANS data are consistent with solvent extraction data suggesting the formation of complexes containing one crown ether and two HDOP dimers. In the extraction of Sr(II) by HDOP alone, the SANS data reveal the presence of small amounts of large aggregates. Both the cis-syn-cis and cis-anti-cis isomers of DCH18C6 inhibit the formation of these aggregates. The cis-anti-cis isomer, however, despite its weaker complexation of strontium, is more effective in preventing aggregate formation.     

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.     

Selectivity in Stripping of Alkali-Metal Cations from Crown Ether Carboxylate Complexes

Abstract

The potential of crown ethers (macrocyclic polyethers) as the next generation of specific extracting agents for metal ions was markedly enhanced by the introduction of crown ethers which bear pendent proton-ionizable groups (1–5). It has been shown that metal ion extraction does not require concomitant transfer of an aqueous phase anion into the organic medium (6). For potential practical applications of these proton-ionizable crown ethers in which hard aqueous phase anions (chloride, nitrate, sulfate) would be involved, this factor is of immense importance. In addition, the combination of ion binding cavities possessing fixed dimensions with protonionizable groups creates novel bifunctional chelating agents. A final factor is the case with which extracted metal ions may be stripped from the organic phase by shaking with aqueous mineral acid.     

The conductivity of non-aqueous electrolyte solutions containing crown-ethers

The conductance of NaI and RbI in acetonitrile solutions at 25°C in presence of different crown-ethers was measured. Analysis of the data in pure acetonitrile and in presence of the crown compounds was carried out using the Fuoss-Onsager-Skinner equations. Addition of crown ethers to the salt solutions generates a decrease in the conductivity in the order of 12-crown-4 < 15-crown-5 < 18-crown-6 < disubstituted 18-crown-6. The difference between the Λ₀ values of the two systems investigated with the same crown compounds decreases as the complexity of the crown-ether used increases. The results, also compared to those of KI systems, are discussed in terms of competitive interaction forces of the crown-ethers and the solvent molecules on the ionic species present in solution.