Interaction of Aluminum with Am(III) and Certain REE(III) Ions in Alkaline Solutions

Precipitates prepared by addition of ammonia or NaOH into solutions containing Al and REE(III) (La, Nd) or Al and Am(III) were studied by thermogravimetry, UV-Vis and IR spectroscopy, X-ray diffraction analysis, and measurement of the dissolution rate. It was shown that the properties of the precipitates containing Al and the second element noticeably differ from the properties of straight aluminum hydroxide precipitate. In the IR spectra, new vibrational bands appear. In the electronic spectra, small shifts of Nd(III) and Am(III) absorption bands relative to the bands of the individual f-element hydroxides are observed. The rates of dissolution of the precipitates in HCl solutions noticeably differ. With increasing pH of coagulation to 13-14, a part of aluminum is captured with the precipitate. However, this fraction is small. In the precipitates obtained from 0.1-1 M NaOH, the interaction of f elements with aluminum is practically lacking.     

Oxidation of Am(III) to Am(IV) with ozone in solutions of heteropolyanions

Oxidation of Am(III) in the presence of K₁₀P2W₁₇O₆₁ and K₈SiW₁₁O₃₉ (L) at 20dGC was studied by spectrophotometry. Am(III) is oxidized with ozone to Am(IV) only in the pH range 3.5–1.0. In the case of formation of a complex with Am: L = 1: 1, the reaction is approximately first-order with respect to the metal, and its rate decreases with a decrease in pH from 3.5 to 1.0. Am(IV) in solution in the presence of ozone is slowly reduced with products of water α-ray radiolysis, predominantly with ?₂?₂. The rate constant of the reaction of Am(IV) with ?₂?₂ was estimated.     

Separation of Am(III) and Pu(IV) at Their Joint Oxalate Precipitation

A procedure was developed for purification of plutonium to remove americium by oxalate precipitation using diethyl oxalate as a precipitant. The developed procedure was tested under laboratory conditions and on an enlarged installation. It was shown that the decontamination factor of plutonium from americium can exceed 2 ×10³. The plutonium oxalate precipitate can be dissolved by heating with HNO₃ in the presence of V(V) catalyst and also by electrochemical dissolution at alternating current.     

Separation of REE(III) and Am(III) by Extraction with Compounds of Zirconium and Dibutyl Phosphoric Acid from Solutions of Nitric and Hydrochloric Acids

Radiochemistry - The behavior of rare-earth elements (REE) and americium during their extraction with compounds of zirconium and dibutyl phosphoric acid (DBPA) in various solvents from solutions of...     

Mechanism of Am(III) oxidation with ozone in carbonate solutions

The reaction of ozone with Am(III) in bicarbonate and carbonate solutions was studied by spectrophotometry. On adding ozone-saturated water to a 2 × 10⁻⁴ M Am(III) solution in 1 M NaHCO₃, about 1/3 of Am remains in the trivalent state and 2/3 is converted to Am(V), with no accumulation of Am(IV). The reaction of Am(III) with ozone involves replacement of H₂O molecules in the coordination sphere of Am(III) by O₃ molecule, followed by elimination of the O₂ molecule. The third O atom remains bonded with Am, converting it to the pentavalent state.     

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.     

Effect of Fe(III) on the extraction of U(VI), Th(IV), and REE(III) from HCl solutions with diphenyl(dibutylcarbamoylmethyl)phosphine oxide

The extraction of U(VI), Th(IV), and REE(III) from HCl solutions with solutions of diphenyl(dibutylcarbamoylmethyl)phosphine oxide in dichloroethane in the presence of Fe(III) was studied. An increase in the Fe concentration in the organic phase leads to a considerable increase in the distribution ratios of U(VI), Th(IV), and REE(III), which is caused by transfer into the organic phase of mixed complexes MCl _m?n (FeCl₄) _n solvated by the extractant molecules. A macroporous styrene-divinylbenzene copolymer impregnated with diphenyl(dibutylcarbamoylmethyl)phosphine oxide can be used for concentrating U(VI), Th(IV), and REE(III) from HCl solutions in the presence of Fe(III).     

Extraction of Am(III) and Eu(III) from Nitric Acid Solutions with Bidentate Neutral Organophosphorus Compounds

Extraction of HNO₃ and microamounts of Am and Eu from nitric acid solutions with solutions of bidentate butyl (phosphorylmethyl)phenylphosphinates R₂P(O)CH₂P(O)Ph(OBu) [R = octyl (I), phenyl (II), p-tolyl (III), p-anisyl (IV)] in 1,2-dichloroethane was studied. The stoichiometry of the extractable complexes was determined, and the apparent extraction constants were calculated. The extractive power of the reagents studied toward HNO₃ increases in the order II < III < IV < I, and toward Am(III), in the order I < II < III < IV.     

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 and sorption preconcentration of U(VI), Am(III), and Pu(IV) from nitric acid solutions with alkylenediphosphine dioxides

The extraction of U(VI), Am(III), and Pu(VI) from nitric acid solutions in the form of complexes with alkylenebis(diphenylphosphine) dioxides and their sorption with POLIORGS F-6 sorbent prepared by noncovalent immobilization of methylenebis(diphenylphosphine) dioxide (MDPPD) on a KhAD-7M? polymeric matrix were studied. The preconcentration conditions and distribution coefficients of U(VI), Am(III), and Pu(IV) in their sorption from 3 M HNO₃ were determined. The possibility of concentrating actinides from multicomponent solutions was demonstrated. The composition and nature of complexes of U(VI) with MDPPD were determined from the ³¹P NMR data.     

Extraction and sorption preconcentration of U(VI), Th(IV), and REE(III) from nitric acid solutions using amine-substituted tetraarylethylenediphosphine dioxides

Extraction of U(VI), Th(IV), and REE(III) from HNO₃ solutions in the form of complexes with amine-substituted tetraarylethylenediphosphine dioxides was studied. The effect of substituents at the P atoms in the extractant molecule on its extraction ability was examined. The stoichiometry of the extractable complexes was determined. The possibility of preconcentration of U(VI), Th(IV), and REE(III) with the complexing sorbent prepared by noncovalent immobilization of the examined extractants on a polymer matrix was demonstrated.     

Solid-Phase Extraction of Eu(III) and Am(III) with Synergistic Mixtures of Extractants

Solid-phase extraction (SPE) of Eu(III) and Am(III) in systems containing a chelating agent and a neutral electron-donor compound was studied. In the systems 1-phenyl-3-methyl-4-benzoylpyrazol-5-one-tetraphenylmethylenediphosphine dioxide and 1-phenyl-3-methyl-4-benzoylpyrazol-5-one-trioctylphosphine oxide, the distribution factors of Eu(III) and Am(III) showed a synergistic effect owing to adduct formation.     

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.     

Selectivity of extraction of U(VI), Th(IV), and REE(III) from perchloric acid solutions with bidentate phosphoryl-substituted butyl phenylphosphinates

Extraction of microamounts of U(VI), Th(IV), and REE(III) from HClO₄ solutions with solutions of bidentate phosphoryl-substituted butyl phenylphosphinates R₂P(O)CH₂P(O)Ph(OBu) [R = phenyl (I), octyl (II)] in dichloroethane was studied. The effect of substituents at the phosphorus atom in the phosphine oxide moiety of these compounds on their extraction ability and selectivity was examined, and the stoichiometry of the extractable complexes was determined. In going from nitric to perchloric acid solutions, the efficiency of the extraction of U(VI) and REE(III) considerably increases, the U/REE separation factors increase, but the Th/U separation factors decrease.     

Extraction of REE(III) Nitrates with Polymer-Supported Trialkylamine

Extraction of HNO₃ and La, Ce, Pr, Nd, and Sm nitrates with polymer-supported trialkylamine C₇-C₉ from 0.5 M HNO₃ containing 1-5 M NaNO₃ is studied. The extraction isotherms are described taking into account formation of (R₃NH)₃[Ln(NO₃)₆] in the extractant phase. The extraction constants decrease in the series La(III)-Sm(III).     

Preconcentration of U(VI), Th(IV), and REE(III) from nitric acid solutions using carbon nanotubes modified with bis(dioctylphosphinylmethyl)phosphinic acid

The extraction of microamounts of U(VI) and Th(IV) from HNO₃ solutions in the form of complexes with bis(dioctylphosphinylmethyl)phenylphosphinic acid was studied. The stoichiometry of the extractable complexes was studied, and the influence of the extractant structure on the efficiency and selectivity of the U(VI) and Th(IV) extraction was examined. U(VI), Th(IV), and REE(III) can be preconcentrated from nitric acid solutions with a complexing sorbent prepared by noncovalent immobilization of bis(dioctylphosphinylmethyl) phosphinic acid on the surface of carbon nanotubes.     

Extraction of Am(III) from Nitric Acid Solutions with Bis(diphenylphosphinylmethyl)phosphinic Acid

Extraction of trace quantities of Am(III) from aqueous HNO₃ solutions with solutions of bis(diphenylphosphinylmethyl)phosphinic acid (I), bis[2-(diphenylphosphinyl)phenoxymethyl]phosphinic acid (II), and bis[2-(diphenylphosphinylmethyl)phenoxymethyl]phosphinic acid (III) in dichloroethane was studied. The stoichiometry of the extractable complexes was determined; the effect of organic diluent on the extraction was considered. The extractive power of the reagents toward Am(III) grows in the order III < II < I. Acid I surpasses in the extractive power a neutral bidentate extractant, tetraphenylmethylenediphosphine dioxide (TPMDPD), by three orders of magnitude. A synergistic effect in extraction of Am with mixtures of TPMDPD and acid I was revealed.     

Extraction of U(VI), Th(IV), Pu(IV), and Am(III) from nitric acid solutions with polyfunctional organophosphorus acids

Extraction of microamounts of U(VI), Th(IV), Pu(IV), and Am(III) nitrates from aqueous HNO₃ solutions with solutions of (diphenylphosphinylmethyl)phenylphosphinic, (di-p-tolylphosphinylmethyl)phenylphosphinic, and (dioctylphosphinylmethyl)phosphinic acids and of butyl hydrogen (diphenylphosphinylmethyl)phosphonate in organic diluents was studied. The metal: extractant stoichiometric ratio in the extractable complexes was determined, and the diluent effect on the extraction efficiency was examined. The possibility of using a macroporous polymeric sorbent impregnated with (dioctylphosphinylmethyl)phenylphosphinic acid for concentrating metal ions from HNO₃ solutions was demonstrated.     

Extraction of Am(III) and Rare-Earth Elements from Nitric Acid Solutions with (Diphenylphosphinylmethyl)phenylphosphinic Acid

Extraction of microamounts of Am, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu nitrates from aqueous HNO₃ with solutions of (diphenylphosphinylmethyl)phenylphosphinic acid in dichloroethane was studied. The stoichiometry of the extractable complexes was determined. Synergistic enhancement of the extraction of rare-earth elements in the presence of tetraphenylmethylenediphosphine dioxide was revealed.     

Extraction of REE(III) Nitrates with Polymer-Supported Trialkylmethylammonium Nitrate

Extraction of La, Ce, Pr, Nd, Sm, and Y(III) nitrates with polymer-supported trialkylmethylammonium nitrate (Aliquat-336) in the presence 1-5 M NaNO₃ in the aqueous phase is studied. The extraction isotherms are described taking into account formation of (R₄N)₂[Ln(NO₃)₅] in the extractant phase. The extraction constants decrease from La to Sm. The extraction constant of Y(III) is considerably lower than those of La(III)-Sm(III).