Extraction of Americium(III) from Nitric Acid Solutions with Neat Diphenyl(dibutylcarbamoylmethyl)phosphine Oxide in the Presence of Metal Salts

Extraction of Am(III) from nitric acid solutions with a liquid complex of diphenyl(dibutylcarbamoylmethyl)phosphine oxide (Ph₂Bu₂) with nitric acid as influenced by concentration of Al, Ca, Na, Ni, Co, Cr, Fe, Zr, and Mo nitrates was studied. Nonextractable (Al, Ca, Na) and poorly extractable (Ni, Co, Cr) nitrates at their widely varied concentration do not interfere with the exhaustive extraction of americium from 3 M HNO3. These salts facilitate both formation of the extraction-active liquid phase on contact of Ph₂Bu₂ with 1 M HNO₃ and exhaustive extraction of americium from the acid. Extraction of Fe(III) at its widely varied concentration insignificantly interferes with extraction of americium, but this effect increases with increasing acidity and phase contact time. Americium is extracted with a powdered reagent from 0.1 M HNO₃ when liquid extractant is not formed in the visible amounts. In extraction of americium from weakly acidic solutions in the presence of salts the solid reagent, apparently, partially transforms into the liquid extractant, and two different extraction mechanisms are operative. It was shown that the neat liquid complex of Ph₂Bu₂ with HNO₃ can be used for exhaustive extraction of americium from high-level saline wastes from plants for processing nuclear fuel.     

Extraction of rare-earth and transplutonium elements with dibutyl hydrogen phosphate in <Emphasis Type="Italic">m</Emphasis>-nitrobenzotrifluoride

The extraction of rare-earth (REE) and transplutonium (TPE) elements, with Ce, Eu, and Am as examples, from aqueous HNO₃ with dibutyl hydrogen phosphate (HDBP) in m-nitrobenzotrifluoride (MNBTF) was studied. The diluent effect on the Eu and Am extraction with dibutyl hydrogen phosphate was examined at various HNO₃ concentrations in the aqueous phase. Based on the data obtained, a mechanism of REE extraction was suggested and the parameters of extraction equations for the initial lanthanide concentrations in the aqueous phase from 0.1 to 100 g l^?1 (counting on metal), HDBP concentration in MNBTF of 0.1–2 M, and HNO₃ concentration in the range 0.5–8 M were calculated. Isotherms of HNO₃ extraction with HDBP solutions of various concentrations were obtained. The possibility of attaining higher concentrations of REE solvates in their extraction with HDBP in MNBTF was demonstrated.     

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.     

Extraction of lanthanide(III) nitrates with composite solid extractants based on a polymeric support impregnated with trialkylmethylammonium nitrate or TBP

Extraction of lanthanides(III) and Y(III) from 1–5 M aqueous NaNO₃ with composite solid extractants based on a polymeric support impregnated with trialkylmethylammonium nitrate (Aliquat-336) or TBP was studied, and the extraction constants were determined. The extraction isotherms were analyzed assuming that lanthanides are extracted with the solid extractants in the form of complexes (R₄N)₂[Ln(NO₃)₅] and Ln(NO₃)₃(TBP)₃.     

Extraction of Rare-Earth Elements and Americium from Nitric Acid Solutions with Polyphosphine Oxides

Extraction of HNO₃ and microamounts of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Am from solutions of NH₄NO₃ and HNO₃ with solutions of polyphosphine oxides containing o-oxyphenylenemethylene fragments in dichloroethane was studied. The stoichiometry of the extractable complexes was determined, and the apparent extraction constants were calculated. As the number of phosphoryl groups in the extractant molecule is increased, the extraction of cerium-group lanthanides increases and that of yttrium-group lanthanides decreases.     

Isolation of Actinides from Irradiated Neptunium and Uranium Targets and Purification with TRU Resin

Within the framework of nuclear-physical experiments on determination of the yields of plutonium and americium isotopes in nuclear reactions ²³⁷Np(³He,xnyp), and also of neptunium and plutonium isotopes in nuclear reactions ²³⁶U(³He,xnyp), a procedure was developed for preparing samples containing americium, plutonium, neptunium, and uranium with a high degree of separation from each other and from the fission and activation products. A new resin for extraction chromatography, TRU-Spec (Eichrom Industries, the United States) was used for isolation of americium, plutonium, neptunium, and uranium from irradiated targets. New data were obtained on the behavior of some fission products in the course of chemical purification with TRU-Spec resin. A procedure was suggested for separation of americium from cerium-group lanthanides.     

Effect of TBP on Extraction of REE and TPE with 4d Element Salts of Dibutylphosphoric Acid

Extraction properties of 4d element (Ti, Zr, and Hf) salts of dibutylphosphoric acid (HDBP) are examined. In extraction of Eu from nitric acid solutions, the optimal [HDBP]/[M] ratio depends on the presence of TBP and a diluent in the extraction system and also on the HNO₃ concentration in solutions. With decane used as a diluent instead of xylene, the distribution coefficients of the extracted elements increase, and the extracting properties of the Zr and Hf salts become more similar. The extraction characteristics of these salts are similar over the entire examined range of HNO₃ concentrations. At the same time, the difference between the Zr and Hf salts in the extractive power applies to all the lanthanides. The extraction properties of the Ti salt strongly differ from those of the Zr and Hf salts. Thorough study of the behavior of the Ti salt is complicated by its limited solubility in organic solvents.     

Separation of Am and Cm by Extraction from Weakly Acidic Nitrate Solutions with Tributyl Phosphate in Isoparaffin Diluent

Trivalent transplutonium (TPE) and rare earth (REE) elements are extracted to more than 80% with 30% TBP in Isopar M from solutions containing 0.06–0.5 M HNO₃ and a salting-out agent, NH₄NO₃, in a concentration of ≥6 M. The elements are stripped from the organic phase with 0.1 M HNO₃. The Am(III)/Eu separation factors vary from 1.8 to 2, which can be used for their extraction separation. The Cm/Am(III) separation factors in 0.06–3 M HNO₃ are in the range from 1.1 to 1.2; therefore, to separate these elements, higher oxidation states of Am, Am(VI) and Am(V), should be used. The effect of various factors on the stability of Am(VI) was examined, and the conditions of the existence of Am(VI) and Am(V) in ≤0.1 M HNO3 solutions containing ~8 M NH₄NO₃ were determined. Curium is extracted with 30% TBP in Isopar M virtually completely, whereas americium only partially (≤30%) passes into the organic phase in the form of Am(III). In the process, high degree of separation of Cm from Am(V) remaining in the aqueous phase is reached (≥99.9%).     

Selective binding of ions of uranium and of transuranium and rare-earth metals with functionally substituted crown ethers

The extraction of uranium and of transuranium and rare-earth elements from nitric acid solutions with solutions of 4,4′(5′)-bis(dialkylphosphoryl)-,-bis(diphenylphosphoryl)-, and-bis[(O-alkyl)phosphoryl]-benzo-n-crown-m ethers (n = 18, m = 6; n = 21, m = 7; n = 24, m = 8) in 1,2-dichloroethane and chloroform was studied. The distribution ratios of U(VI), Pu(IV), Am(III), and Eu(III) in the extraction depend both on the experimental conditions and on the structural features of the ligands. In the range [HNO₃] = 0.02–1.0 M, the metal distribution ratios D _M depend on the mutual steric orientation of the phosphoryl groups. With the cis (4,4′) isomers, D _M is higher than with the trans (4,5′) isomers and with the isomer mixtures. With the compound containing the (n-BuO)₂P(O) groups in the cis position as example, it was found that the highest distribution ratios D _U = 0.98 were observed in 3 M HNO₃; D _Pu = 5.1, in 0.5 M HNO₃; and D _Am = 0.007, at pH 2. For the trans conformer under the same conditions, D _M of U(VI), Pu(IV), and Am(III) is 0.091, 1.8, and 0.003, respectively. The macroring size (number of carbon atoms n), under other conditions equal, also significantly affect the extraction activity of the reagent. With the extraction of Am(III) from 0.01–3 M HNO₃ as example, it was shown that the crown ethers with n = 21 are the most efficient with all the substituents. The maximum of D _Am shifts toward higher HNO₃ concentrations with increasing n. The coordinating power of phosphoryl-containing ligands based on functionally substituted benzo-21-crown-7 ether in the extraction of Am(III) from 0.01–3 M HNO₃ decreases in the order (n-BuO)(OH)P(O)-? (n-BuO)₂P(O)-> Ph₂P(O)-, under other conditions equal. The extraction ability of di(n-BuO)(OH)P(O)-dibenzo-21-crown-7 (D _Am = 814 in extraction from 0.1 M HNO₃) exceeds that of the other compounds studied by more than two orders of magnitude. Conditions were found for the selective extractive separation of Am(III) and Eu(III) using bis[(O-alkyl)(OH)phosphoryl]dibenzo-21-crown-7, with a separation factor of >90 at [HNO₃] = 0.01 M.     

Radiation-Chemical Resistance of Anion Exchangers and Safety of Sorption Processes in Nitric Acid Solutions: III. Radiation-Chemical Resistance of VP-1AP Anion Exchanger

Variation of physicochemical characteristics of VP-1AP anion-exchange resin in HNO₃ solutions on heating and under the action of external -radiation up to the absorbed dose of 5 MGy was studied. It was shown that at thermal treatment of anion exchanger with increasing HNO₃ concentration and temperature and under the action of ionizing radiation the total exchange capacity (TEC) and capacity with respect to strongly basic groups (C _{s b g}) decrease. The swelling coefficients K _{s w} noticeably vary only in treatment in 12 M HNO₃ solutions and reach a maximum of 1.4. In this case, the specific surface area of the sorbent decreases from 15.7 to 1.2 m² g^{- 1}. Under the action of ionizing radiation the specific surface area of the irradiated anion exchanger somewhat increases and reaches 18 m² g^{- 1}.     

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).     

Extraction of lanthanide nitrates with trioctylmethylammonium di(2,4,4-trimethylpentyl)phosphinate

A binary extractant based on trioctylmethylammonium di(2,4,4-trimethylpentyl)phosphinate R₄NA was prepared. The extraction of lanthanide (Gd-Lu) nitrates from aqueous solutions with 0.6 M toluene solutions of R₄NA and trioctylmethylammonium nitrate was studied. The extraction isotherms of lanthanide nitrates with these extractants were obtained and physicochemical and mathematical models of extraction of lanthanides were developed. The extraction isotherms with the binary extractant were analyzed assuming that the Ln(III) extractable complexes LnA₃, (R₄N)₂[Ln(NO₃)₅], (R₄N)₃[Ln(NO₃)₆], (R₄N)₂[Ln(NO₃)₃A₂], and (R₄N)[Ln(NO₃)₃A] [A is di(2,4,4-trimethylpentyl)phosphinate anion] are formed in the organic phase. The extraction constants were calculated.     

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.     

Enhancement of titania by doping rare earth for photodegradation of organic dye (Direct Blue)

Lanthanide ions (La³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, and Yb³⁺)/doped TiO₂ nanoparticles were successfully synthesized by sol–gel method. Their photocatalytic activities were evaluated using Direct Blue dye (DB53) as a decomposition objective. The structural features of TiO₂ and lanthanide ions/TiO₂ were investigated by XRD, SEM, UV-diffuse reflectance, and nitrogen adsorption measurements. Our findings indicated that XRD data characteristic anatase phase reflections and also XRD analysis showed that lanthanides phase was not observed on Lanthanide ions/TiO₂. The results indicated that Gd³⁺/TiO₂ has the lowest bandgap and particle size and also the highest surface area and pore volume (V_p) as well. Lanthanide ions can enhance the photocatalytic activity of TiO₂ to some extent as compared with pure TiO₂ and it was found that Gd³⁺/TiO₂ is the most effective photocatalyst. The photocatalytic tests indicate that at the optimum conditions; illumination time 40 min, pH ∼4, 0.3 g/L photocatalyst loading and 100 ppm DB53; the dye removal efficiency was 100%. Details of the synthesis procedure and results of the characterization studies of the produced lanthanide ions/TiO₂ are presented in this paper.     

Regular Trends in Variation of Crystal Structures of Actinide Metals and Their Alloys

The regular trends in variation of crystal structures of 5f actinide metals in their alloys, under theaction of a high pressure, also in alloys of 4f lanthanide metals with plutonium can by explained by par-ticipation of 5f electrons in formation of the interatomic bond. By analogy with the criterion R _m R _4f (the ratio of "metallic" radius R _m to the radius of 4f shell), used for lanthanide metals, the ratio of the metallic radius to the radius of the trivalent ion (R _m/R ^{3 +}) was selected as a measure of this participation. The changes occurring in crystal lattices of americium, curium, and samarium in their alloys with plutonium, phase transitions in transplutonium metals under a high pressure, and also the order of variation of metallic radii along the actinide series are considered.     

Synergic extraction of Ce(III) from HNO<Subscript>3</Subscript> solutions with a mixture of CCD and HDBP ZS in a polar diluent

The extraction of Ce(III) from HNO₃ solutions with a mixture of chlorinated cobalt dicarbollide (CCD) and dibutyl hydrogen phosphate (HDBP) or its zirconium salt (HDBP ZS) in m-nitrobenzotrifluoride was studied by the method of isomolar series. A considerable synergic effect S was observed, reaching a maximum in a mixture of HDBP with CCD at the molar ratio HDBP : CCD = 7 : 1 (S = 100). The highest Ce(III) distribution ratios D _Ce are observed with mixtures of CCD and HDBP ZS (1 : 6 and 1 : 4). An increase in the HNO₃ concentration causes changes in D _Ce and S to different extents depending on the type of HDBP ZS. The synergic effect was attributed to the formation of coordination compounds that are more hydrophobic than the initial compounds and have stronger bonds of Ce(III) with the ligands.     

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.     

Synergistic extraction of rare earth elements from HNO3 solutions with a mixture of CCD and HDBP in a polar diluent

The extraction of Ln(III) (except Pm), La(III), and Y(III) from HNO3 solutions with dibutyl hydrogen phosphate (HDBP), chlorinated cobalt dicarbollide (CCD), and their mixture in a polar diluent, mixture of o-chloronitrobenzene (OCNB) and CCl₄ (1: 1), was studied. A synergistic effect is observed for all the examined elements. For the series La-Dy, it reaches a maximum at the HDBP to CCD molar ratio of 3: 1, and for the series Tb-Lu, at the HDBP to CCD molar ratio of 9: 1. The synergistic effect is observed at the HDBP to CCD molar ratios of up to 700: 1 and 1500: 1 for heavy and light lanthanides, respectively. At higher ratios, the magnitude of the synergistic effect does not exceed the uncertainty of its determination. This fact indicates that one CCD molecule can activate several hundreds of HDBP molecules, enhancing their extraction ability. The degrees of separation of neighboring lanthanides do not noticeably change on introducing CCD into the extraction system. The key component of the hypercomplex is the CCD anion, with the role of the CCD proton being insignificant. A complex of variable composition, containing lanthanide, CCD, and HDBP, is formed in the organic phase.     

Study of Extraction of Palladium from Nitric Acid Solutions with Nitrogen-Containing Compounds,as Applied to Recovery of Fission Palladium from Spent Nuclear Fuel of Nuclear Power Plants: 2. Effect of Radiation on Palladium Recovery and Condition of Extraction Systems

Extraction of palladium nitrate complexes from 1-3 M HNO₃ with tri-n-octylamine (TOA) and tricaprylmethylammonium nitrate (Aliquat 336 nitrate) in diethylbenzene under irradiation at a dose of up to 100 W h l^{- 1} is studied. In irradiated extraction systems, the acidity of the aqueous and organic phases decreases and HNO₂ is formed. With increasing radiation dose the degree of Pd recovery decreases by virtue of partial degradation of the organic phase. The radiation effects on the condition of extraction systems are discussed.     

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

Extraction of HNO₃ and trace amounts 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 dibutyl diphenylphosphinylmethylphosphonate in dichloroethane was studied. The stoichiometry of the extractable solvates was determined, and the apparent extraction constants were calculated.