Andrew H. Bond

Novel Extraction of Chromatographic Resins Based on Tetraalkyldiglycolamides: Characterization and Potential Applications

Abstract Two new extraction chromatographic resins containing the diglycolamide class of molecules have been prepared and characterized, and potential applications identified. The new resins consist of 40 weight percent N,N,N′N′ tetraoctyldiglycolamide (TODGA) and N,N,N′N′ tetrakis‐2‐ethylhexyldiglycolamide (TEHDGA) sorbed onto 50–100 µm particle size Amberchrom® CG‐71. The new resins have capacities for Eu of approximately 0.086 mmol/mL of bed and are quite stable to extractant leaching. The resins were characterized by measuring the batch uptake of actinides, lanthanides, and yttrium, alkaline earths and 13 selected transition and post‐transition elements from HNO3 and HCl. Based on the uptake data, a number of very efficient separations were achieved using 0.5–2 mL bed volume columns and room temperature operation.

Metal ion separations in polyethylene glycol-based aqueous biphasic systems : correlation of partitioning behavior with available thermodynamic hydration data

Abstract Solvent extraction, utilizing an oil-water mixture (e.g, chloroform-water) and a suitable complexant, is a proven technology for the selective removal and recovery of metal ions from aqueous solutions. Aqueous biphasic systems (ABS), formed by mixing certain inorganic salts and water-soluble polymers, or by mixing two dissimilar water-soluble polymers, have been studied for more than 40 years for the gentle, non-denaturing separation of fragile biomolecules, yet ABS have been virtually ignored as a possible extraction technology for metal ions. In this report we review our metal ion partitioning work and discuss the three major types of partitioning: (1) those rare instances that the metal ion species present in a given solution partitions to the PEG-rich phase without an extractant; (2) the use of halide salts which produce a metal anion complex that partitions to the PEG-rich phase; and (3) the use of a water-soluble extractant which distributes to the PEG-rich phase. In addition, we correlate the partitioning behavior we observed with available thermodynamic data for metal ions and their complexes.

Metal Ion Separations in Polyethylene Glycol-Based Aqueous Biphasic Systems

Solvent extraction utilizing an oil-water mixture (e.g., chloroform-water) and a suitable complexant, is a proven technology for the selective removal and recovery of metal ions from aqueous solutions. Aqueous biphasic systems (ABS), formed by mixing certain inorganic salts and water-soluble polymers, or by mixing two dissimilar water-soluble polymers, have been studied for more than 40 years for the gentle, non-denaturing separation of fragile biomolecules, yet ABS have been virtually ignored as a possible extraction technology for metal ions. In this report we review our metal ion partitioning work and discuss the three major types of partitioning: (1) those rare instances that the metal ion species present in a given solution partitions to the PEG-rich phase without an extractant; (2) the use of halide salts which produce a metal anion complex that partitions to the PEG-rich phase; and (3) the use of a water-soluble extractant which distributes to the PEG-rich phase. In addition, we correlate the partitioning behavior we observed with available thermodynamic data for metal ions and their complexes.

Influence of aggregation on the extraction of trivalent lanthanide and actinide cations by purified Cyanex 272, Cyanex 301, and Cyanex 302

Summary The extraction of trivalent lanthanide (Sm3+, Eu3+) and actinide (Am3+, Cm3+) cations from 1.0 M NaNO3 into n-dodecane solutions of bis(2,4,4-trimethylpentyl)phosphinic acid (HC272), bis(2,4,4-trimethylpentyl)monothiophosphinic acid (HC302), and bis(2,4,4-trimethylpentyl)dithiophosphinic acid (HC301) is reported. In each case, the dependence of the distribution ratios on the total extractant concentration is approximately second power. Using NMR, the dimerization constant of HC301 is determined to be 0.67 ± 0.06 at 25.0 °C in deuterated n-heptane, implying that the average aggregation of the extractant changes greatly across the extractant concentration range studied. When the effect of aggregation is considered for each of the extractants, the stoichiometries of the extracted complexes are found to be M(H(C272)2)3, M(C302)3, and M(C301)3.

Crown ether complexes of lead(II) nitrate. Crystal structures of the 12-crown-4, 15-crown-5, benzo-15-crown-5 and 18-crown-6 complexes

Abstract The straightforward reaction of common crown ethers with Pb(NO3)2 in CH3CN and CH3OH mixtures has produced several crystalline complexes which have been structurally characterized. Crystallographic analysis reveals the following formulations: [Pb(NO3)(12-crown-4)2][Pb(NO3)3(12-crown-4)] (1), [PbL2][Pb(NO3)3L]2 (L=15-crown-5 (2) or benzo-15-crown-5 (3)), and [Pb(NO3)2(18-crown-6)] (4). As anticipated the cavity size of 18-crown-6 matches the ionic radius of Pb2+ and the lead ion resides exactly in the center of the crown ether. For all four structures, the PbO separations range from 2.645(8)–3.06(1) A (crown ether) and 2.53(1)–2.809(8) A (nitrate). Variations in bond distances are noted relating to differences in coordination number, geometry and ionic charge, however, a lone pair effect is not distinguished. The crystallographic parameters are as follows: 1: monoclinic, P21/c with (at 22 °C) a=8.237(5), b=28.464(9), c=16.331(8) A, β=93.77(7)°, Dcalc=2.07 g cm−3 for Z=4 formula units, and R=0.038 utilizing 4596 independent observed (Fo⩾5σ(Fo)) reflections; 2: orthorhombic, Pccn with (at 22 °C) a=37.462(5), b=9.586(2), c=17.378(4) A, and Dcalc=2.00 g cm−3 for Z=4 (severe disorder precluded a complete structure determination); 3: triclinic, P 1 with (at 22 °C) a=10.392(2), b=18.799(6), c=21.069(8) A, α=112.11(3), β=98.01(2), γ=104.32(2)°, Dcalc=1.92 g cm−3 for Z=2, and R=0.052 (8505 reflections); 4: monoclinic, P21/c with (at 22 °C) a=8.171(8), b=15.499(9), c=7.856(8) A, β=105.08(7)°, Dcalc=2.06 g cm−3 for Z=2 and R=0.034 (1018 reflections).

PARTITIONING BEHAVIOR OF 99Tc AND,129I FROM SIMULATED HANFORD TANK WASTES USING POLYETHYLENE-GLYCOL BASED AQUEOUS BIPHASIC SYSTEMS

ABSTRACT Three simulated Hanford tank wastes, SY-101, NCAW, and SST, were prepared and contacted with aqueous solutions of 20-60% (w/w) polyethylene glycol (PEG)-2000. The combined salting out action of OH-, C03 2’, SO4 2rsquo;, PO4 3\ and possibly other minor constituents in the waste simulants, results in the formation of aqueous biphasic systems (ABS). Investigation of the partitioning behavior of 99Tc (as 99Tc04) and 129I (as 99T) from the waste simulant phase to the upper PEG-rich phase at 25 and 50°C revealed distribution ratios as high as 190 for 99Tc04 and 7.5 for 129I. The partitioning of several of the other major species in these solutions (Na+, P04 3, C03 2’, S04 2\ PEG), as well as the general physical characteristics of the ABS were also investigated. In general, the observed distribution ratios are affected (increased if they prefer the PEG-rich phase, decreased if they prefer the salt-rich phase) by increasing the concentration of PEG-2000 used to form the ABS which increases the differenc...

Isomer Effects in the Extraction of Metal Ionsfrom Acidic Nitrate Media by Dicyclohexano-18-crown-6†

The extraction of Strontium and potassium from nitric acid by the cis-syn-cis and cis-anti-cis isomers of dicyclohexano-18crown-6 (DCH18C6) in 1-octanol is examined. Both isomers are shown to extract significant amounts of undissociated nitric acid. This extraction, along with the formation of metal-nitrato and metal-crown ether complexes in the aqueous phase, is shown to be important in determining the efficiency of metal ion extraction by the two isomers. The DCH18C6 isomer yielding the more efficient extraction of potassium or Strontium is shown to depend upon the crown ether concentration and the aqueous nitric acid concentration.

The crown ether extraction of group 1 and 2 cations in polyethylene glycol-based aqueous biphasic systems at high alkalinity

The crown ethers 1,4,7,10,13-pentaoxacyclopentadecane (15- crown-5) and 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) have been utilized to study the partitioning of Group 1 and 2 cations between aqueous layers in an aqueous biphasic system formed by the salting out of PEG-2000 (polyethylene glycol of 2000 average molecular weight) with NaOH. Partitioning to the PEG-rich phase is generally only achieved by the addition of high concentrations of NaNO,. In the presence of NO3-, the metal ion partitioning results correlate with the log K values for 18-crown-6 complexation in H,O. This trend does not hold for 15-crown-5.

Aqueous Biphase Systems for Liquid/Liquid Extraction of f-Elements Utilizing Polyethylene Glycols

Abstract Aqueous biphasic systems formed by adding a H2O soluble polymer (polyethylene glycol) to an aqueous salt solution ((NH4)2SO4 or K2CO3) have been investigated for use in extracting aqueous Am3+, Pu4+, UO2 2+, and Th4+ ions into the polymer-rich phase. Extraction occurs only in the presence of complexing dyes which preferentially partition to the polymer-rich phase. Three such dyes, arsenazo III, alizarin complexone, and xylenol orange were investigated. Arsenazo III extracts all four metal ions from SO4 2- media but not from CO3 2- solutions. Alizarin complexone quantitatively extracts Th4+ and Pu4+ from SO4 2- media, while Am3+ is the best extracted ion in CO3 2- solution. Xylenol orange extracts only Am3+ from CO3 2- media. In SO4 2- solutions low concentrations of xylenol orange extract Th4+ and Pu4+, while Am3+ and UO2 2+ are extracted at higher concentrations of xylenol orange. H2SO4 can be used to strip the metal ions, while NH4OH often but not always enhances the extraction.

STRUCTURAL STUDIES OF POLYETHER COORDINATION TO MERCURY(II) HALIDES: CROWN ETHER VERSUS POLYETHYLENE GLYCOL COMPLEXATION

Abstract The crystal structures of several crown ether and polyethylene glycol complexes of HgX2 (X=Cl, Br, I) have been investigated. The crown ether complexes studied are [HgX2(18-crown-6)] (X=Br, I) and [HgI2(dibenzo-18-crown-6)]·CH3CN. In each case Hg resides in the cavity of the ether resulting in hexagonal bipyramidal geometry with axial, terminal halides. The covalently bonded halides reside closer to Hg than the oxygen donor atoms. Five polyethylene glycol complexes have been structurally characterized: [(HgCl2)3(EO3)], [HgX2(EO4)] (X=Br, I), [HgCl2(EO5)], and [HgBr2(EO5)HgBr2]2 (EO3=triethylene glycol, EO4=tetraethylene glycol, EO5=pentaethylene glycol). The EO4 and EO5 glycols mimic crown ethers by forming an equatorial girdle around Hg although in each case one alcoholic terminal end does not coordinate to the metal ion. Each complex also has two covalent, nearly linear, axial halides coordinated to Hg. In [(HgCl2)3(EO3)], the glycol is linear and coordinates to three Hg atoms all on the same s...