Evaluation of long chain monoamide extractants for the reprocessing of U–Pu–Zr metallic fuel solution

Long chain monoamide extractants, N,N-di-decyloctanamide(DDOA), N,N-di-hexyldecanamide(DHDA), N,N-di-2-ethylhexyloctanamide(D2EHOA) and N,N-dihexyl-2-ethylhexanamide(DH2EHA) were synthesized and studied for the recovery of U(VI), Pu(IV) and Zr(IV) from a simulated dissolver solution of un-irradiated U–Zr metallic fuel. The results were compared with the results of N,N-dihexyloctanamide(DHOA) and tri-n-butylphosphate(TBP) under similar conditions. Solvent extraction studies were carried out for comparing the extraction behavior of U(VI), Pu(IV) and Zr(IV) in monoamide extractants with TBP system. The influence of length and branching of alkyl chains on either side of the amidic group on the extraction efficiency, third phase behaviour and metal ion selectivity in long chain monoamides has been discussed based on the results of above studies.

     

Uranium and Plutonium Extraction by N,N-dialkylamides Using Multistage Mixer-settler Extractors

N,N-Dialkylamides (monoamides) are known as extractants for U and Pu, and many studies have been carried out mainly by single-stage batch method. We have focused on two monoamides: N,N-di(2-ethylhexyl)-2,2-dimethylpropanamide (DEHDMPA) and N,N-di(2-ethylhexyl)butanamide (DEHBA), and proposed a multistage extraction process for recovering U and Pu by these monoamides. A continuous counter-current experiment was carried out to demonstrate the validity of this process. This process consisted of two cycles, and the 1st cycle and the 2nd cycle employed DEHDMPA and DEHBA as extractants, respectively. The feed solution for the 1st cycle was 5.1 mol/dm³ (M) nitric acid containing 0.92 M U, 1.6 mM Pu, and 0.6 mM Np. The raffinate collected in the 1st cycle was used as the feed for the 2nd cycle. The ratios of U recovered in the U fraction and U-Pu fraction were 99.1% and 0.8%, respectively, and the ratios of U in the used solvents were <0.04%. The ratio of Pu recovered in the U-Pu fraction was 99.7%, and the ratio of Pu in the used solvents was in the order of 10^–3–10^–4%. The concentration ratio of U with respect to Pu in the U-Pu fraction was 9, and this indicated that Pu was not isolated. The decontamination factor of U with respect to Pu in the U fraction was obtained as 4.5×10⁵. These results supported the validity of the proposed process.     

Synthesis,characterization, thermogravimetry,and structural study of uranium complexes derived from dibasic S-alkylated thiosemicarbazone ligands

Two pentagonal bipyramidal complexes, ethanol-(S-ethyl-N¹,N⁴-bis(3-methoxy-2-hydroxybenzaldehyde)-isothiosemicarbazide-N,N′,O,O′)-dioxidouranium(VI) (1) and ethanol-(S-ethyl-N¹-(2-hydroxyacetophenone)-N⁴-(5-bromo-2-hydroxybenzaldehyde)-isothiosemicarbazide-N,N′,O,O′)-dioxidouranium(VI) (2), have been prepared and characterized. Their structures have been determined by X-ray crystallography, and the structural parameters are discussed with those observed in related complexes. Electronic absorption, proton magnetic resonance, and FT-IR spectra have been recorded and analyzed. In both complexes, the U(VI) centers are surrounded by N₂O₂ donor ligands, two oxido groups, and one ethanol in a distorted pentagonal bipyramid. The thermal stability of the new complexes has also been determined.     

Transport of U(VI) from sulphuric acid medium across supported liquid membrane (SLM) containing di-(2-ethylhexyl) phosphoric acid (D2EHPA)/n-dodecane as a carrier

This paper reports on the supported liquid membrane (SLM) based transport studies of U(VI) from sulphate medium using di-(2-ethylhexyl) phosphoric acid/n-dodecane as carrier. Polytetrafluoroethylene membrane was used as solid support and H₂SO₄ as receiver phase. The effects of various parameters such as receiver phase concentration, feed acidity, carrier concentration, U(VI) concentration, membrane thickness and membrane pore size on U(VI) transport had been investigated. With increase in H₂SO₄ concentrations and pH of feed solution there is an increase in U(VI) transport across the SLM. Similarly with increase in membrane thickness the U(VI) transport decrease whereas in case of pore size variation reverse results are obtained. The membrane thickness variation results showed that the U(VI) transport across the SLM is entirely diffusion controlled and the diffusion coefficient the D _(o) was calculated as 1.36 × 10^?7 cm² s^?1. Based on optimized condition, a scheme had been tested for selective recovery of U(VI) from ore leach solution containing a large number of other metal ions.     

Affinity of An(VI) for N4-Tetradentate Donor Ligands: Complexation of the Actinyl(VI) Ions with N4-Tetradentate Ligands

In this report the affinity of four N₄-tetradentate ligands that incorporate the 2-methylpyridyl functionality with hexavalent actinides $(\mathrm{AnO}_{2}^{2+})$ has been investigated in methanol solution. The ligands studied include N,N??-bis(2-methylpyridyl)diaminoethane (BPMDAE), N,N??-bis(2-methylpyridyl)-1,3-diaminopropane (BPMDAP), N,N??-bis(2-pyridylmethyl)piperazine (BPMPIP), and trans-N,N-bis(2-pyridylmethyl)-1,2-diaminocyclohexane (BPMDAC). Conditional stability constants describing the strength of the interaction were determined by UV?Cvisible spectrophotometry. The log₁₀ K ₁₀₁ values for both U(VI) and Pu(VI) are comparable and show the same trend of stability with ligand structure. Dinuclear complexes are also indicated as being important. The log₁₀ K ₂₀₁ values for Pu(VI) complexation with the N₄-ligands are identical for the four ligands (within experimental error), indicating that the structure of the ligand backbone has little effect on the stability of the (PuO₂)₂L²⁺ complex. The exception to this trend is the behavior of N,N??-bis(2-pyridylmethyl)piperazine (BPMPIP) with Pu(VI). This ligand displays a tendency to reduce Pu(VI) within the experimental time frame of 45 minutes. BPMPIP is the only ligand tested that contains tertiary amines in the ligand backbone. The decomposition of BPMPIP by Pu(VI) suggests a susceptibility of tertiary amines to oxidative degradation.     

The effect of previous gamma-irradiation on the extraction of U(VI), Th(IV), Zr(IV), Eu(III) and Am(III) by various amides

The extraction behavior of U(VI), Th(IV), Zr(IV), Eu(III) and Am(III) from 3.5M nitric acid with a series of gamma-pre-irradiated symmetrical and unsymmetrical monoamides in benzene has been investigated up to a dose of 100 Mrad. The results indicated that the radiolytic stability is influenced by the structure of amides. Symmetrical monoamides seem to be less affected by radiation compared with unsymmetrical monoamides. Infrared studies identify the final products of radiolysis as the respective carboxylic acids and amines. The radiolytic degradation of the investigated monoamides has been estimated by quantitative IR spectroscopy. Extraction data obtained under similar experimental conditions for U(VI), Th(IV) and Zr(IV) with the TBP/benzene system have also been compared. This revised version was published online in August 2006 with corrections to the Cover Date.     

Extraction of U(VI) with N,N′-dimethyl-N,N′-dioctylmalonamide from nitrate media

The extraction of uranyl nitrate with the novel extractant N,N′-dimethyl-N,N′-dioctylmalonamide (DMDOMA) from aqueous sodium nitrate (and nitric acid) was investigated. The extraction mechanism was established and the stoichiometry of the main extracted species confirms to UO₂(NO₃)₂ · DMDOMA. The IR spectral study was also made of the extracted species. Methyl substituent improves the extraction ability of malonamide for U(VI) compared with that of N,N,N′,N′-tertrabutylmalonamide (TBMA).     

Selective uranium adsorption using modified acrylamide resins

Polymeric matrices composed of N,N′-Methylenebis(acrylamide)/glycidyl methacrylate was prepared and modified producing two resins (GMA/MBA/OH and GMA/MBA/SO₃H). The adsorption of U(VI) ions onto the modified acrylamide resins was studied from synthetic and granite samples. For better understanding around the uranium mineralization and the rock-forming minerals of the hosted granitic rocks, to facilitate the choice of the appropriate ore-processing techniques, it was necessary to identify the mineral composition and the radiometric specifications of the used granitic rock. The synthesized adsorbents revealed a promising selective adsorption toward the U(VI) ions from its bearing solutions even with the competence of other cations.

     

Exit reactor Thetis/Ghent (1967–2003): A recollection of its significant contribution to NAA and its leading role in the development of the k<Subscript>0</Subscript>-standardization

Resins with monoamides as functional groups have been synthesized and their fundamental adsorption behaviors have been examined for selective recovery of uranium(VI) from nitric acid media. The resins synthesized with porous silica support showed greatly different adsorptions for U(VI) depending on the chemical structures of the functional group. Some resins show little or no adsorption for U(VI) from 0.1 to 6 mol/dm³ HNO₃. While, resins consisting of dimethylacrylamide (DMAA) showed an increasing adsorption with an increasing concentration of HNO³ up to 9 to 12 mol/dm³. Other ions were not found to be adsorbed onto Silica-DMAA under similar solution conditions, which means that the resin is selective for U(VI) in HNO₃ media.     

8-Aminoquinoline as a new bidentate ligand for cis-MoO2: synthesis and characterization of a dioxomolybdenum(VI) amide [MoO2(NHC9H6N)2]

The reaction of (Bu₄N)₂[Mo₆O₁₉] with 8-aminoquinoline in the presence of DCC (N,N′-dicyclohexylcarbodiimide) afforded the cis-dioxo-Mo(VI) amide [MoO₂(NHC₉H₆N)₂], which was characterized by spectroscopy, mass spectrometry, ¹H NMR, and single-crystal X-ray analysis. X-ray crystallography shows that the complex exhibits a distorted octahedral geometry with each oxo ligand trans to the quinolyl nitrogen and the amido ligands are bound to the metal in an N,N-chelating fashion. The molecules form zigzag chains via C–H?···?O hydrogen bonds and the chains are connected into networks through interchain N–H?···?O hydrogen bonds.     

Synthese,EPR und Röntgenkristallstrukturanalyse von mer-Trichloro(2,2′-bipyridin)nitridotechnetium(VI), einem neuen Nitridokomplex des Technetium(VI)

Synthesis, EPR and X-Ray Structure of mer-Trichloro(2,2′-bipyridine)nitridotechnetium(VI) — a new Technetium(VI) Nitrido Complex mer-Trichloro(2,2′-bipyridine)nitridotechnetium(VI) has been prepared by the reaction of (NBu₄)[TcNCl₄] with 2,2′-bipyridine in acetonitrile, whereas the same procedure gives in methanol the technetium(V) cation [TcNCl(bipy)₂]⁺. The EPR spectrum of [TcNCl₃(bipy)] suggests a meridional coordination of the three chloro ligands. [TcNCl₃(bipy)] crystallizes monoclinic in the space group P2₁/n; a = 8.572(1), b = 15.462(1), c = 10.110(1) Å, β = 104.21(1)°, Z = 4. The R value converged at 0.034 on the basis of 3 040 reflections. The technetium atom is distorted octahedrally coordinated with the chloro ligands meridionally cis with respect to the nitrido nitrogen. The Tc? N(1) bond length is 1.669(4) Å, and the Tc? N(3) bond (2.371(4) Å) is significantly lengthened due to the structural trans labilizing influence of the “N^3?” ligand.     

Preparation and Characterisation of Bis (η5-Cyclopentadienyl) N,N-Disubstituted Dithiocarbamato Chloro Oxotungsten (VI) Complexes

Bis (η⁵-cyclopentaienyl) N,N-disubstituted dithiocarbamato chloro oxotungsten (VI) complexes of the type η⁵-Cp₂WO(S₂CNR₂)Cl and η⁵-Cp₂WO(S₂CNRR')Cl (where R=Me, Et and i-Pr and R'=Cyhx) have been prepared by the reaction of bis (η⁵-cyclopentadienyl) oxotungsten (VI) dichloride with sodium salts of dithiocarbamic acids in refluxing tetrahydrofuran. Infrared spectral studies demonstrate that in these complexes dithiocarbamate ligands are bidentate. Therefore, tungsten (VI) atom may be assigned a coordination number 6 in all these complexes. Elemental analyses of these compounds have also been carried out. Electronic spectra have been recorded for all the six complexes.     

Four cytotoxic N4‐substituted thiosemicarbazones derived from 2‐hydroxynaphthalene‐1‐carboxaldehyde

The X‐ray crystal structures are reported of four novel and potentially O,N,S‐tridentate donor ligands that demonstrate antitumour activity. These ligands are 1‐[(4‐methyl­thio­semicarbazono)methyl]‐2‐naphthol, C₁₃H₁₃N₃OS, (III), 1‐[(4‐ethylthio­semicarbazono)­methyl]‐2‐naphthol, C₁₄H₁₅N₃OS, (IV), 1‐[(4‐phenyl­thio­semicarbazono)­methyl]‐2‐naphthol, C₁₈H₁₅N₃OS, (V), and 1‐[(4,4‐di­methyl­thio­semicarbazono)­methyl]‐2‐naphthol di­methyl sulfoxide solvate, C₁₄H₁₅N₃OS·C₂H₆OS, (VI). These chelators are N4‐substituted thio­semicarbazones, each based on the same parent aldehyde, namely 2‐­zhydroxynaphthalene‐1‐carboxaldehyde isonicotinoylhydrazone. Conformational variations within this series are discussed in relation to the optimum conformation for metal‐ion binding.     

Weitere Reaktionen von 1,3-Dichlordisilazanen und 1,3-Dichlordisiloxanen

Zusammenfassung Spezielle Umsetzungen von 1,3-Dichlordisilazanen werden beschrieben. Die Umsetzung mit einem bestimmten Amin führte zu einer SiNSiN-Verbindung mit 6 verschiedenen Substituenten (I; Rk. 1). Analog bildeten sich mit Hydrazinen Bis(hydrazino)-disilazane der Strukturgruppe NNSiNSiNN (II, III; Rk. 2). Mit Äthylendiamin konnte ein Si₂N₃C₂-Siebenringsystem (IV), mit Bis(trimethylsilyl)harnstoff ein Sechsringsystem Si₂N₃C (VI), mit Diphenylsilandiol das Cyclotrisildioxazan-Sechsringsystem (VIII, IX) aufgebaut werden. 1,3-Dichlordisiloxan ergab in ähnlichen Umsetzungen erstmalig ein Si₂N₂OC₂-Siebenringsystem (V) und ein Si₂N₂OC-Sechsringsystem (VII).

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New reactions of 1.3-dichlorodisilazanes and 1.3-dichlorodisiloxanes. (chemistry of silicon-nitrogen compounds, XCVIII)

Special reactions of 1.3-dichlorodisilazanes give a) with a special amine a SiNSiN-compound with 6 different substituents (I; equ. 1); b) with hydrazines bis(hydrazino)disilazanes of the structural unit NNSiNSiNN (II, III; equ. 2); c) with ethylenediamine a novel Si₂N₃C₂-sevenmembered ring system (IV); d) with bis(trimethylsilyl)urea a sevenmembered ring system Si₂N₃C (VI); e) with diphenylsilanediol the cyclotrisildioxazane ring system (VIII, IX). Analogous reactions of 1.3-dichlorodisiloxanes lead to the novel sevenmembered ring system Si₂N₂OC₂ (V) and to the sixmembered Si₂N₂OC-ring system (VII).

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97. Mitt.:U. Wannagat, L. Gerschler undH. J. Wismar, Mh. Chem.102, 1834 (1971).

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Vorläufige Mitt. von Teilergebnissen:U. Wannagat, Angew. Chem.77, 626 (1965); Pure appl. Chem.13, 262 (1966).

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Mit Auszügen aus den DissertationenE. Bogusch, Techn. Hochschule Graz 1966, undF. Rabet, Techn. Univ. Braunschweig 1971, sowie nach Arbeiten vonP. Geymayer, Techn. Hochschule Graz 1965.     

Solid state N and C NMR study of dioxomolybdenum (VI) complexes of Schiff bases derived from trans-1,2-cyclohexanediamine

The ¹³C, ¹⁵N CP MAS NMR and FT-IR spectra of dioxomolybdenum (VI) complexes of trans-N,N′-bis-(R-salicylidene)-1,2-cyclohexanediamine (R=H, R=3,5-diCl, R=3,5-diBr, R=4,6-diOCH₃), trans-N,N′-bis-(2-OH-naphthylidene)-1,2-cyclohexanediamine and trans-N-(salicylidene)-N′-(2-OH-naphthylidene)-1,2-cyclohexanediamine have been measured. Comparative analysis of the NMR and IR spectra of the complexes with those of the corresponding ligands has shown that the complexation of the di-Schiff bases leads to changes in the conformation of the ligands and the charge redistribution. The asymmetric structure and non-planar structure of the complexes have been suggested.     

Intramolecular hydrogen‐bond‐directed coordination: trans‐bis(N‐benzoyl‐N′‐propyl­thio­urea‐κS)di­iodo­platinum(II) and trans‐bis(N‐benzoyl‐N′‐propyl­thio­urea‐κS)di­bromo­platinum(II)

In the title compounds, trans‐[PtI₂(C₁₁H₁₄N₂OS)₂], (I), and trans‐[PtBr₂(C₁₁H₁₄N₂OS)₂], (II), respectively, intramolecular N—H⋯O (propyl­amine side) hydrogen bonds in the potentially bidentate thio­urea ligands lock the carbonyl O atoms into six‐membered rings, determining the S‐mono­dentate mode of coordination of these ligands. Intramolecular N—H⋯X (X is I or Br) interactions (benzoyl­amine side) lead to slight distortions of the Pt^II coordination spheres from ideal square‐planar geometry. The Pt^II ion is located on an inversion centre in both structures.     

Retention of uranium(VI) by laumontite, a fracture-filling material of granite

Retention of U(VI) by laumontite, a fracture-filling material of granite was investigated by conducting dynamic and batch sorption experiments in a glove-box using a granite core with a natural fracture. The hydrodynamic properties of the granite core were obtained from the elution curve of a non-sorbing tracer, Br⁻. The elution curve of U(VI) showed a similar behavior to Br⁻. This reveals that the retention of U(VI) by the fracture-filling material was not significant when migrating through the fracture at a given condition. From the dynamic sorption experiment, the retardation factor R _a and the distribution coefficient K _a of U(VI) were obtained as about 2.9 and 0.16 cm, respectively. The distribution coefficient (K _d ) of U(VI) onto laumontite obtained by conducting a batch sorption experiment resulted in a small value of 2.3±0.5 mL/g. This low K _d value agreed with the result of the dynamic sorption experiment. For the distribution of uranium on the granite surface investigated by an X-ray image mapping, the fracture region filled with laumontite showed a relatively lower content of uranium compared to the surrounding granite surface. Thus, the low retention of U(VI) by the fracture-filling material can be explained by following two mechanisms. One is that U(VI) exists as anionic uranyl hydroxides or uranyl carbonates at a given groundwater condition and the other is the remarkably low sorption capacity of the laumontite for U(VI).     

Solvent extraction of uranium(VI) and thorium(IV) by N,N′-di-p-tolylpyridine-2,6-dicarboxamide from nitric acid solution

Synthesis and characterization of N,N′-di-p-tolylpyridine-2,6-dicarboxamide (DTPDA) was carried out and used for extraction of U(VI) and Th(IV) from nitric acid solutions. The processes of extraction were determined by the slope analysis and by analyzing a function that allows the simultaneous treatment of all the experimental points obtained in different conditions. The different factors affecting the extraction distribution ratio(D) of U(VI) and Th(IV) (extraction concentration, concentrations of nitric acid, salting-out agent NaNO₃ concentration, equilibration time and temperature) were investigated. The results obtained indicated that the extraction species of U(VI) and Th(IV) are mainly extracted as UO₂(NO₃)₂·1.5DTPDA and Th(NO₃)₄·1.5DTPDA. The related thermodynamic functions were calculated. Back-extraction of U(VI) and Th(IV) from organic phases was also studied.     

Effects of electron-rich ancillary ligands on green and yellow-emitting bis-cyclometalated iridium complexes

Abstract

Six new green to yellow-emitting heteroleptic bis-cyclometalated iridium(III) complexes of the type Ir(C?N)₂(L?X) (C?N?=?cyclometalating ligand, L?X?=?monoanionic chelating ancillary ligand) bearing two widely used cyclometalating ligands (C?N?=?2-(2-thienyl)pyridine (thpy) and 2-phenylbenzoxazole (bo)) and six different ancillary ligands were prepared. In this study, the complexes include structurally diverse ancillary ligands that allow us to investigate several aspects of structure-property relationships. Ancillary ligands used in this study are small-bite-angle N-phenylacetamidate (paa), N-isopropylbenzamidate (ipba) and N,N′-diisopropylbenzamidinate (dipba), and larger bite-angle β-ketoiminate (acNac), β-diketiminate (NacNac), and β-thioketoiminate (SacNac). The emission color is governed by the choice of the cyclometalating ligand, but the ancillary ligands influence the electrochemical and photophysical properties. Electrochemical analysis shows that the energy of the HOMO varies substantially as the L?X structure is altered, whereas the energy of LUMO remains nearly constant. The emission maxima range from 537?nm to 590?nm, with solution quantum yields between 0.0094 and 0.60 and microsecond lifetimes. The results here reveal the ancillary ligands provide a channel to control redox properties and excited-state dynamics in cyclometalated iridium complexes that luminesce in the middle regions of the visible spectrum.