Tamara J. Haverlock

A Striking Effect of Ionic‐Liquid Anions in the Extraction of Sr2+ and Cs+ by Dicyclohexano‐18‐Crown‐6

Abstract The nature of the ionic‐liquid (IL) anion has been found to have a remarkable effect on the solvent extraction of Sr2+ and Cs+ by dicyclohexano‐18‐crown‐6 dissolved in ionic liquids. In particular, the extraction efficiency increases with the hydrophobicity of the IL anion as reflected by the solubility in water of ILs having a common cation. Since a cation‐exchange mechanism is operating in these systems, the influence of the IL anion is in large part attributable to an expected Le Chatelier effect in which a greater aqueous concentration of IL cation, obtained when using an IL anion of lower hydrophobicity, opposes cation exchange. This dependence is opposite to that found for IL cations, indicating a significant advantage of using ILs with hydrophobic anions for cation extraction. Furthermore, the extraction selectivity for Sr2+ over Na+, K+, and Cs+ can be significantly improved through the use of hydrophobic anions for the ILs containing 1‐ethyl‐3‐methylimidazolium or 1‐butyl‐3‐methylimidazolium cations.

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.

Analysis of Equilibria in the Extraction of Cesium Nitrate by Calix[4]arene-bis(t-Octylbenzo- Crown-6) in 1,2-Dichloroethane

The extraction of CsNO3 by the highly lipophilic calixarene-crown ether calix[4]arene-bis(t-octylbenzo-crown-6) (CABOBC6) in 1,2-dichloroethane (1,2-DCE) at 25 °C has been shown to be consistent with the formation of both 1 : 1 and 2 : 1 metal : ligand species. Variation of the aqueous-phase CsNO concentration up to 1.0 M and variation of the organic-phase calixarene concentration up to 0.10∼M was modeled by the program SXLSQI. Formation of the organic-phase species CsBNO3 (B = calixarene) was confirmed as well as the organic-phase dissociation products CsB+ and NO3-. Good evidence for the 2 : 1 metal : ligand organic-phase species Cs2B(NO3)2 was also found, although the dissociation of nitrate from this complex was not observed. Binding of the second Cs+ cation by the ligand is approximately two orders of magnitude weaker than binding of the first Cs+ cation. The logarithm of the apparent partition ratio (log PB) of the calixarene between water and 1,2-DCE was found by 1H-NMR techniques to be > 5.1.

SOLVATOCHROMIC SOLVENT POLARITY MEASUREMENTS OF ALCOHOL SOLVENT MODIFIERS AND CORRELATION WITH CESIUM EXTRACTION STRENGTH

Solvatochromic solvent polarity measurements reveal that the cesium extraction strength afforded by solutions composed of calix[4]arene-bis-(tert-octylbenzocrown-6) at 0.005 M in 1,2-dichloroethane containing a variety of novel alcohol phase modifiers at 0.25 M correlates well with the hydrogen-bond donor (HBD) ability of the alcohol. The alcohols comprise a small library of derivatives of 2-(4-tert-octylphenoxy)-1-ethanol, in which the alcohol carbon atom contains a substituent of variable electron-withdrawing ability. The betaine dye 4-(2,4,6-triphenylpyridinium)-2,6-diphenylphenoxide, also known as Dimroth-Reichardt dye #30, was used to obtain ET(30) and ET N values. Alcohols containing substituents with fluorine atoms gave rise to both higher ET N values and higher cesium distribution values. The trend observed in HDB parallels the expected trend in alcohol acidity. †This research was sponsored by the Office of Science, Office of Basic Energy Sciences, U.S. Department of Energy, under contract number DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC.

Dideoxygenated calix[4]arene crown-6 ethers enhanced selectivity for caesium over potassium and rubidium

Calix[4]arene crown-6 ethers derived from dideoxygenated calix[4]arene exhibit enhanced extraction selectivity for caesium over potassium; the crystal stucture of the uncomplexed calix[4]arene monobenzocrown-6 ether exists in the 1,3-alt conformation in the solid state.

Synthesis and Properties of Calix[4]arene‐bis[4‐(2‐ethylhexyl)benzo‐crown‐6], A Cesium Extractant with Improved Solubility

Abstract The new cesium‐selective macrocycle calix[4]arene‐bis[4‐(2‐ethylhexyl) benzo‐crown‐6] (“BEHBCalixC6”) has been found to have improved solubility in a modified alkane diluent over calix[4]arene‐bis(4‐tert‐octylbenzo‐crown‐6) (“BOBCalixC6”). The synthesis of this new calixcrown extractant, together with its solubility and extraction properties, is described in this report. The solubility, cesium extraction, and potassium loading behavior are compared with those of BOBCalixC6, the macrocycle currently employed in the caustic‐side solvent extraction (CSSX) process for extracting cesium from alkaline nitrate solutions such as high‐level nuclear waste. Replacement of the tert‐octyl alkyl chains on the benzo‐crown portion of the calixcrown by 2‐ethylhexyl chains improves the equilibrium solubility of the free calixcrown in aliphatic diluents while not affecting the cesium extraction strength. Equilibrium concentrations of BEHBCalixC6 in Isopar L diluent modified with 0.5 M 1‐(2,2,3,3‐tetrafluoropropoxy)‐3‐(4‐sec‐butylphenoxy)‐2‐propanol (Cs‐7SB) over the course of 41 weeks of gentle agitation at 25°C maintained the initial concentration of 57 ± 2 mM, with no evidence of precipitation or third‐phase formation. In contrast, 57 ± 2 mM solutions of BOBCalixC6 prepared using sonication were not stable, with precipitation occurring to afford an equilibrium concentration of only 6.7 ± 0.2 mM after 41 weeks. Third‐phase tests showed that BEHBCalixC6 resists third‐phase formation as well as, or better than, BOBCalixC6. With increasing potassium loading from an alkaline sodium nitrate solution, both calixcrowns at 20 mM in modified Isopar L exhibited comparable onset of third‐phase formation, gauging by the decreasing mass balance in cesium extraction from the same solutions. However, the BEHBCalixC6 solvent exhibited no visible indications of third‐phase formation until the aqueous potassium concentration reached 0.75 M, whereas the BOBCalixC6 suffered visible third‐phase formation when the aqueous potassium nitrate concentration reached 0.25 M. Calixcrowns with higher solubility in alkane diluents may find application in cesium extraction from waste matrices containing moderate (≥0.2 M) quantities of potassium, such as that stored at the US Department of Energys Hanford Site, where higher concentrations of the calixcrown extractant may be required to obtain practical cesium distribution coefficients for process flowsheets.

Binding Cesium Ions with Nucleosides: Templated Self-Assembly of Isoguanosine Pentamers

[*] Prof. J. T. Davis, M. Cai, Dr. A. L. Marlow, Dr. J. C. FettingerDepartment of Chemistry and BiochemistryUniversity of MarylandCollege Park, MD 20742 (USA)Fax: ( ⁄1)301-314-9121E-mail: jd140@umail.umd.eduProf. D. FabrisDepartment of Chemistry and BiochemistryUniversity of MarylandBaltimore County, Baltimore, MD 21228 (USA)T. J. Haverlock, Dr. B. A. MoyerChemical and Analytical Sciences DivisionOak Ridge National Laboratory, P.O. Box 2008Oak Ridge, TN 37831-6119 (USA)[**] This research was supported by the Separations and AnalysisProgram, Division of Chemical Sciences, Office of Basic EnergySciences, U.S. Department of Energy. J.T.D. thanks the DreyfusFoundation for a Teacher-Scholar Award. We thank Drs. BryanEichhorn, Steve Rokita, and Lyle Isaacs for advice.Supporting information for this article is available on the WWWunderhttp://www.wiley-vch.de/home/angewandte/ or from the author.

Aqueous leachability of lanthanide and plutonium titanates

Abstract The leachabilities of titanate and zircono-titanate solid solutions, Ce 2 Ti 2 O 7 , Er 1.78 Ce 0.22 Ti 2 O 7 , Er 1.78 Pu 0.22 Ti 2 O 7 (9.5 wt% Pu) Er 1.78 Ce 0.22 Ti 0.5 Zr 1.5 O 7 , SrCe 2 Ti 4 O 12 , SrPu 2 Ti 4 O 12 (50.7 wt% Pu) and Sr 2 Ce 2 Ti 5 O 16 , have been investigated in WIPP ‘A’ brine, 0.1 M NaCl, and 0.1 M HCl solutions using a modified MCC-3 procedure with a duration of 60 days. The concentrations of plutonium leached by the brine were less than 1 ppm. Where cerium was used as a surrogate for plutonium, its concentration in WIPP brine was below the limit of detection (10 ppm) established for the inductively coupled plasma (ICP) atomic emission spectrometer used. Concentrations of strontium leached by WIPP brine from stable strontium-containing titanate compounds, considered as possible immobilizers of both 90 Sr and actinide elements, were on the order of 30–60 ppm.

Enhanced liquid–liquid anion exchange using macrocyclic anion receptors: effect of receptor structure on sulphate–nitrate exchange selectivity

When certain macrocyclic anion receptors are added to a chloroform solution of the nitrate form of a lipophilic quaternary ammonium salt (methyltri-C8,10-ammonium nitrate, Aliquat 336N), the extraction of sulphate from an aqueous sodium nitrate solution via exchange with the organic-phase nitrate is significantly enhanced. Eight macrocycles were surveyed, including two derivatives of a tetraamide macrocycle, five derivatives of calix[4]pyrrole and β-decafluorocalix[5]pyrrole. Under the hypothesis that the enhancement originates from sulphate binding by the anion receptors in the chloroform phase, it was possible to obtain reasonable fits to the sulphate distribution survey data based on the formation of 1:1 and 2:1 receptor:sulphate complexes in the chloroform phase. Apparent 1:1 sulphate-binding constants obtained from the model in this system fell in the range . Comparison of the results for the various anion receptors included in this study reveals that sulphate binding is sensitive to the nature of the substituents on the parent macrocycle scaffolds in a way that does not follow straightforwardly from simple chemical expectations, such as electron-withdrawing effects on hydrogen-bond donor strength.

Compounds of cerium, titanium and oxygen

Abstract The solubility of Ce 2 Ti 2 O 7 in Ln 2 Ti 2 O 7 (LnGd, Er and Lu) was determined experimentally. It was found that the solubility increases as the ionic radius of the host lanthanide element decreases. The lattice parameters of Ce 2 O 3. 4TiO 2 have been measured. The solubility of TiO 2−m in Ce 2 O 3 .3TiO 2−m ( m ≈0.11) was determined and the resulting solutions were investigated; the results indicate that an additional 2.5 TiO 2− m can be dissolved without significantly changing the lattice parameters. Limits for the solubility of Ce 4+ in compounds such as Ce 2 O 3 . n TiO 2 in which n =2 or 4 were also estimated.