Sorption recovery of U(VI), Pu(IV), and Am(III) from nitric acid solutions with solid-phase extractants based on Taunit carbon nanotubes and polystyrene supports

Sorption procedures were developed for recovering U(VI), Pu(IV), and Am(III) with solid-phase extractants (SPEs) prepared by impregnation of Taunit carbon nanotubes and polystyrene supports with diphenyl( dibutylcarbamoylmethyl)phosphine oxide (CMPO) and tri-n-octylphosphine oxide (TOPO) The impregnation and actinide recovery were performed in the batch mode and using microcolumns. Procedures for support impregnation and SPE preparation are described. Conditions were found for sorption recovery of U(VI), Pu(IV), and Am(III) from 3 M HNO₃ solutions. The possibility of actinide desorption was demonstrated. The effect of macrocomponents on the degree of actinide recovery was examined.     

Solid-phase extractant with dipicolinic acid N,N’-diethyl-N,N’-di(p-tolyl)diamide for preconcentration and separation of actinides and lanthanides

The sorption ability of a solid-phase extractant with dipicolinic acid N,N’-diethyl-N,N’-di(p-tolyl) diamide groups on fibrous polyacrylonitrile (PAN) matrix was studied. The conditions for immobilization of the reagent on PAN disks were determined, and the possibility of sorption preconcentration and separation of U(VI), Pu(IV), Am(III), and Eu(III) from 2–6 M HNO₃ solutions was examined. The solid-phase extractant obtained exhibits good kinetic properties and can be used for separation of Am(III) + EU(III).     

Extraction of U(VI), Th(IV), and rare-earth elements from nitric acid solutions with phosphoryl-and carbonyl-containing podands

The distribution of HNO₃ and microamounts of nitrates of U(VI), Th(IV), La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y between aqueous solutions of HNO₃ and solutions of N,N′-dimethyl-N,N′-diphenyl-3-oxapentanediamide (I) and 1,3-bis(diphenylphosphinoyl)-2-oxapropane (II) in organic diluents was studied. The stoichiometry of the extractable complexes was determined, and the effect exerted by the extractant structure and by the organic diluent on the efficiency of recovery of rare-earth elements (REE) into the organic phase was examined. In nitric acid solutions, carbonyl-containing podand I surpasses in the extraction ability phosphoryl-containing podand II. The possibility of using a macroporous polymeric sorbent impregnated with compound I for recovering REE from nitric acid solutions was demonstrated. Original Russian Text A.N. Turanov, V.K. Karandashev, V.E. Baulin, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 3, pp. 226–232.     

Extraction of U(VI), Th(IV), and REE(III) from nitric acid solutions with (N,N-dialkylcarbamoylmethyl)- and (N-alkylcarbamoylmethyl)phenylphosphinic acids

Extraction of microamounts of U(VI), Th(IV), and REE(III) from HNO₃ solutions with solutions of (N,N-dialkylcarbamoylmethyl)- and (N-alkylcarbamoylmethyl)phenylphosphinic acids in dichloroethane was studied. The stoichiometry of the extractable complexes was determined, and the influence exerted on the efficiency of the U(VI), Th(IV), and REE(III) recovery into the organic phase by the extractant structure, organic diluent, and aqueous phase composition was examined. The possibility of selective recovery and concentration of U(VI), Th(IV), and REE(III) from nitric acid solutions with a complexing sorbent prepared by noncovalent immobilization of the examined polyfunctional organophosphorus acids on a macroporous polymeric matrix was demonstrated.     

Extraction properties of polyfunctional P,N-containing podands with diphenylphosphorylacetamide terminal groups in nitric acid solutions

The extraction of HNO₃ and microamounts of U(VI), Th(IV), Sc(III), and REE(III) nitrates from HNO₃ solutions with dichloroethane solutions of phosphorus-containing podands containing two terminal Ph₂P(O)CH₂C(O)NH groups linked by a di-or triethylene glycol chain was studied, and the stoichiometry of the extractable metal complexes was determined. The compounds extract the metal ions from nitric acid solutions more efficiently than does (dibutylcarbamoylmethyl)diphenylphosphine oxide. With increasing length of the polyethylene glycol chain, the extraction of HNO₃ increases, but the degree of recovery of REE(III) ions from HNO₃ solutions of the concentration exceeding 3 M decreases.     

Extraction of U(VI), Th(IV), and REE(III) from nitrate solutions with diaryl(dialkylcarbamoylalkyl)phosphine oxides containing a dialkylcarbamoylmethyl substituent in the alkylene bridge

The extraction of microamounts of U(VI), Th(IV), and REE(III) from HNO₃ and NH₄NO₃ solutions with solutions of diaryl(dialkylcarbamoylalkyl)phosphine oxides containing a dialkylcarbamoylmethyl substituent in the alkylene bridge was studied. The stoichiometry of the complexes extracted from nitric acid solutions with N,N,N',N'-tetrabutyl-2-(di-p-anisylphosphinyl)butanedioic diamide I was determined. The influence of the extractant structure and aqueous phase composition on the efficiency and selectivity of the extraction of U(VI), Th(IV), and REE(III) into the organic phase was examined. Introduction of the–CH₂C(O)NAlk₂ fragment into the methylene bridge of the diaryl(dialkylcarbamoylmethyl)phosphine oxide molecule considerably enhances the extraction of REE(III) from neutral nitrate solutions. Such modification of the extractant molecule only slightly influences the extraction of REE(III) from nitric acid solutions, but leads to a considerable increase in the U(VI) extraction and to a decrease in the Th(IV) extraction. The selectivity of the extraction of U(VI) and REE(III) is thus considerably increased.     

Extraction of metal ions from aqueous solutions of mineral acids with crown ether-ionic liquid systems

The extraction of U(VI), Sr, and Cs from solutions of mineral acids (HNO₃, HCl) with a crown ether, cis-syn-cis-dicyclohexyl-18-crown-6 (DCH18C6-A), dissolved in ionic liquids (ILs), 1-butyl-3-methyl-imidazolium derivatives (bmimPF₆, bmimBF₄, bmimTf₂N), was studied. The best physicochemical characteristics (solubility in the aqueous phase, viscosity, hydrophobicity, etc.) are exhibited by a solution of DCH18C6-A in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (bmimTf₂N). The metal distribution ratios (D _M) in the extraction with a 0.01 M DCH18C6-A solution are 80 for CsNO₃, 78 for CsCl, and 162 for Sr(NO₃)₂. With an increase in the HNO₃ and HCl concentrations, D _M decreases, and with 1 M acids it does not exceed 1. The U(VI) extraction from nitric acid solutions with a 1 M solution of DCH18C6-A in bmimTf₂N initially increases with an increase in the aqueous phase acidity, with D _U(VI) reaching 5.4 in 4 M HNO₃, but then decreases in the interval 4–8 M HNO₃, whereas in the extraction with a 1 M solution of tributyl phosphate (TBP) in bmimTf₂N D _U(VI) monotonically increases with an increase in the HNO₃ concentration to 8 M. From hydrochloric acid solutions, U(VI) is extracted with solutions of DCH18C6-A in bmimTf₂N with the D _U(VI) values characteristic of solutions of DCH18C6-A in nonpolar organic diluents. On the whole, ILs as solvents exhibit unusual properties in the extraction of alkali and alkaline-earth elements from neutral solutions and of U(VI) with TBP from concentrated nitric acid solutions.     

Extraction of REE(III), U(VI), and Th(IV) from Nitric Acid Solutions with Carbamoylmethylphosphine Oxides in the Presence of Bis[(trifluoromethyl)sulfonyl]imide Ions

Extraction of microamounts of REE(III), U(VI), and Th(IV) with solutions of carbamoylmethylphosphine oxides (CMPOs) in organic diluents from aqueous HNO₃ solutions containing lithium bis[(trifluoromethyl) sulfonyl]imide (LiTf₂N) was studied. The efficiency of the REE(III), U(VI), and Th(IV) extraction from nitric acid solutions with CMPO solutions considerably increases in the presence of Tf₂N^– ions in the aqueous phase. The stoichiometry of the extractable complexes was determined, and the influence of the structure of the CMPO molecule, kind of organic diluent, and aqueous phase composition on the efficiency of the U(VI), Th(IV), and REE(III) extraction into the organic phase was considered.     

Synthesis, thermal, photoluminescent, and electroluminescent properties of a novel quaternary Eu(III) complex containing a carbazole hole-transporting functional group

A novel quaternary Eu(III) complex containing a carbazole fragment as hole-transporting functional group was synthesized, and its thermal stability, photoluminescent (PL), electroluminescent (EL) properties were studied. Its glass transition temperature (T _g) was 131 °C and 5% weight loss temperature was 325 °C. In studies of its EL properties, two devices with the Eu(III) complex as red light-emitting materials were fabricated and measured. Device 1: ITO/NPB (40 nm)/Eu(III) complex (30 nm)/Alq₃ (30 nm)/LiF (0.7 nm)/Al (100 nm), NPB was N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine as the hole-transporting layer, Alq₃ was tris(8-hydroxyquinoline) aluminum as the electron-transporting layer. Device 1 gave two emission bands of the Eu(III) complex and Alq₃ with the maximum luminance of 437 cd/m² at 17.34 V, and its turn-on voltage was 10 V. In device 2, an electron-transporting/hole-locking layer of BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 30 nm) was added between the Eu(III) complex and Alq₃ layers, only a sharp red emission band of the Eu(III) complex was given with the maximum luminance of 186 cd/m² at 20.08 V, and its turn-on voltage was 12 V.     

Recovery of actinides from their dioxides using organic reagents saturated with nitric acid

The TBP-HNO₃ and N,N′-dimethyl-N,N′-dioctylhexylethoxymalonamide-HNO₃ adducts effectively recovery actinides from solid solutions of their oxides in UO₂ matrix. The adduct of methyl isobutyl ketone and HNO₃ selectively recovers uranium from PuO₂-UO₂ solid solution, separating uranium from plutonium. The optimal composition of TBP-HNO₃ adducts for the recovery of actinides from the dioxide solid solutions was determined. Uranium is recovered with the adduct more rapidly at lower temperatures and smaller volume of the organic phase, as compared to the dissolution of the oxide fuel in aqueous nitric acid. This approach to the processing of spent nuclear fuel can substantially decrease the volume of highly toxic radioactive aqueous and organic wastes arising with the existing technologies.     

Multistage extraction separation of Am(III) and Cm(III) in planet centrifuges

Countercurrent chromatography (CCC), a support-free partition chromatography, allows realization of multistep extraction separations in specially designed planet centrifuges. Highly efficient Am(III)/Cm(III) separation in nitric acid solutions in the dynamic mode was obtained using two-phase systems based on diamide extractants such as N, N-dimethyl-N,N-dibutyltetradecylmalonamide (DMDBTDMA), N,N-dimethyl-N,N-dioctylhexylethoxymalonamide (DMDOHEMA), and N,N-dimethyl-N,N-dibutyldodecylethoxymalonamide (DMDBDDEMA). All these extractants could be recommended to use for CCC separation of ²⁴³Am and ²⁴⁴Cm. Increasing coil length and decreasing pumping rate of the mobile phase increase the stationary phase retention in the column and improves the resolution of the Am(III) and Cm(III) elution curves. The basic chromatographic parameters of the column (number of theoretical plates and peak resolution of the elements to be separated) are optimized. CCC could be used for separation of elements with similar properties and also for testing quality of radionuclidic products. Single-stage chromatographic separation, when realized under optimal conditions, gives the Cm fraction containing 99.5% Cm(III) and 0.6% Am(III), and the Am fraction containing 99.4% Am(III) and 0.5% Cm(III). Separation is carried out by the isocratic elution method.Translated from Radiokhimiya, Vol. 46, No. 6, 2004, pp. 549–554.Original Russian Text Copyright © 2004 by Maryutina, Litvina, Malikov, Spivakov, Myasoedov, Lecomte, Hill, Madic.     

Extraction of f Elements and Technetium from HNO3 Solutions with Solutions of Alkyl (N,N-Diethylcarbamoylmethyl)phenylphosphinates

Phosphinic acid derivatives, alkyl (N,N-diethylcarbamoylmethyl)phenylphosphinates (ADPs) were synthesized, studied, and tested as extractants for f elements and technetium at the Mayak Production Association. The distribution factors of these elements D were studied in relation to the ADP and HNO₃ concentrations. The influence exerted by the structure of the alkoxy group at the P atom on DAm and DEu in extraction of Am(III) and Eu(III) (chosen as examples) from nitric acid solutions with solutions of ADPs in dichloroethane was examined. The differences between the distribution factors of Am(III), Pu(IV), U(VI), and Tc(VII) are sufficiently high for complete separation of these elements with a high degree of purification in one step of extraction with ADP solutions. The changes observed in the IR spectrum of the 2-ethylhexyl ADP upon complexation with Pr(III) suggest high complexing power of this reagent toward lanthanide ions. The spectrometric data suggest bidentate coordination of the metal with the chelating groups of the reagent.     

Extraction of REE(III), U(VI), and Th(IV) from HNO<Subscript>3</Subscript> and HClO<Subscript>4</Subscript> solutions with (α-pyridyl)tetraphenylmethylenediphosphine <Emphasis Type="Italic">N,P,P</Emphasis>'-trioxide

Extraction of microamounts of U(VI), Th(IV), and REE(III) from HNO₃ and HClO₄ solutions with solutions of (α-pyridyl)tetraphenylmethylenediphosphine N,P,P'-trioxide in dichloroethane was studied. The stoichiometry of the extractable complexes was determined, and the influence of the extraction structure and aqueous phase composition on the efficiency and selectivity of the extraction of U(VI), Th(IV), and REE(III) into the organic phase was studied. Introduction of the pyridine N-oxide fragment into the methylene bridge of the tetraphenylmethylenediphosphine dioxide molecule to obtain (α-pyridyl)tetraphenylmethylenediphosphine N,P,P'-trioxide leads to a decrease in its ability to extract U(VI), Th(IV), and REE(III) from nitric acid solutions, whereas the U/REE separation factors increase. The REE(III) extraction efficiency considerably increases in going from nitric acid to perchloric acid solutions.     

Extraction of rare-earth elements from nitric acid solutions with bidentate neutral organophosphorus compounds in the presence of l-butyl-3-methylimidazolium hexafluorophosphate

The distribution of microamounts of La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y nitrates between aqueous HNO₃ solutions and solutions of tetraphenylmethylenediphosphine dioxide, diphenyl(diethylcarbamoylmethyl)phosphine oxide, and dibutyl(diethylcarbamoylmethyl)phosphine oxide in organic solvents in the presence of l-butyl-3-methylimidazolium hexafluorophosphate (BMImPF₆) was studied. The stoichiometry of the extractable complexes was determined. The influence of the HNO₃ concentration and the nature of the extractant and organic solvent on the synergistic effect observed in the REE extraction in the presence of BMImPF₆ in the organic phase was analyzed. The possibility of using a macroporous polymeric sorbent impregnated with a mixture of tetraphenylmethylenediphosphine dioxide and BMImPF₆ for the recovery of REE(III), U(VI), and Th(IV) from HNO₃ solution was demonstrated.     

Transmission electron microscopy study on the superstructure and the precipitation of γ′-Fe4N in initially homogeneous ɛ-iron nitride powders

Annealed and quenched ɛ-Fe_2-3N powders with an initially homogeneous composition of Fe₃N_1.0 were studied by transmission electron microscopy (TEM). TEM specimens were successfully prepared from the powder using a sandwiching technique. The superstructure in ɛ-powders was identified as ɛ′-Fe₃N type (space group P6₃22), and no other type of superstructure was observed. γ′-Fe₄N nitride precipitated from ɛ powders as individual grains during the annealing process, which is different from the typical fine lamellar structure observed in bulk iron-nitride samples. The observed orientation relationships between γ′ and ɛ grains are also different from that reported in the lamellar structure of bulk iron-nitride samples. This suggests that in the powder investigated by us there is no one specific orientation of the precipitated γ′ grains with respect to the parent ɛ grains.     

Interaction of InAs and InSb with aqueous solutions of nitric acid

InSb dissolution in 7.8–15.6 N HNO₃ is controlled by the oxidizer diffusion to the surface. InAs dissolution in 15.6 N HNO₃ is controlled by diffusion in solution; at low acid concentrations, the dissolution rate is limited by diffusion through the loose oxide layer forming on the sample surface. The different dissolution kinetics of InAs and InSb in HNO₃ can be explained by the different properties of the surface layers of hydrous arsenic and antimony oxides.     

Synthesis and property study on Eu(III) complexes of modified poly(N-isopropylacrylamide)

Poly(N-isopropylacrylamide) with aromatic end groups (Ar-PNIPAM) were synthesized by atom transfer radical polymerization of N-isopropylacrylamide in isopropanol using phenyl 2-chloropropionate, (4′-phenyl)phenyl 2-chloropropionate, and (2′,6′-diphenyl)phenyl 2-chloropropionate as initiators and CuCl/tris(2-dimethylaminoethyl)amine (Me₆TREN) as a catalytic system. The resulting polymers had narrow polydispersity index of 1.10–1.14 and molecular weights of 3700–4600 g mol⁻¹. Then, novel functional complexes of Ar-PNIPAM, Europium(III) (Eu(III)), and α-Thenoyltrifluoroacetone (TTA) (Ar-PNIPAM/Eu(III)/TTA) with thermosensitive and fluorescent properties were synthesized and characterized by Fourier transform infrared spectra and fluorescence spectroscopy. Metal Eu(III) was not only bonded to oxygen and nitrogen atoms of polymer chain in PNIPAM, but also bonded to TTA. The maximum emission intensity of the complexes at 613 nm was enhanced about 22, 27, 33 times compared with that of the corresponding Eu(III). The lower critical solution temperatures (LCSTs) of Ar-PNIPAM/Eu(III)/TTA were slightly greater compared with that of PNIPAM. Eu(III) complexes had excellent fluorescence performance, the fluorescence spectrum presented characteristic emission of Eu(III) at 613 nm.     

Properties of magnetic poly(glycidyl methacrylate) and poly(N-isopropylacrylamide) microspheres

Iron oxide colloids were prepared by coprecipitation of Fe(II) and Fe(III) salts in alkaline media and stabilized by perchloric acid, oleic acid, or poly(acrylic acid). In an attempt to obtain magnetic polymer microspheres differing in size, dispersion polymerization of glycidyl methacrylate (GMA) in ethanol containing HClO₄-stabilized magnetite, dispersion copolymerization of GMA and 2-hydroxyethyl methacrylate (HEMA) in toluene/2-methylpropan-1-ol mixture in the presence of oleic acid-coated magnetite, and inverse suspension copolymerization of N-isopropylacrylamide (NIPAAm) and N,N′-methylenebisacrylamide (MBAAm) in cyclohexane in the presence of poly(acrylic acid)-coated maghemite were compared. The microspheres were characterized by morphology, size, polydispersity, and some magnetic properties.     

Extraction of U(VI), Th(IV), and REE(III) from Nitric Acid Solutions with 2,6-Bis(diphenylphosphorylmethyl)pyridine <Emphasis Type="Italic">N</Emphasis>-Oxide

The extraction of microamounts of U(VI), Th(IV), and REE(III) from HNO₃ solutions in the form of complexes with 2,6-bis(diphenylphosphorylmethyl)pyridine N-oxide (I) was studied in relation to the kind of organic diluent and to the HNO₃ concentration in the equilibrium aqueous phase. The stoichiometry of the extractable complexes was determined. With respect to the ability to extract Th(IV) and REE(III), compound I considerably surpasses tetraphenylmethylenediphosphine dioxide and tetraalkyl-substituted analogs of I.     

Preparation of nanocrystalline VMg(OH)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> and VO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> · MgO from organometallic precursors

A process is proposed for the synthesis of nanocrystalline VMg(OH) _x and VO _x · MgO with specific surface areas of up to 1200 and 470 m²/g, respectively. The synthesized VO _x · MgO oxides consist of nanocrystals (2′–5 nm), which form platelike agglomerates. As distinct from conventional impregnation of magnesium oxide, the aerogel process for VO _x · MgO synthesis ensures a uniform vanadium distribution in MgO.