Differentiating between trivalent lanthanides and actinides

The reactions of LnCl(3) with molten boric acid result in the formation of Ln[B(4)O(6)(OH)(2)Cl] (Ln = La-Nd), Ln(4)[B(18)O(25)(OH)(13)Cl(3)] (Ln = Sm, Eu), or Ln[B(6)O(9)(OH)(3)] (Ln = Y, Eu-Lu). The reactions of AnCl(3) (An = Pu, Am, Cm) with molten boric acid under the same conditions yield Pu[B(4)O(6)(OH)(2)Cl] and Pu(2)[B(13)O(19)(OH)(5)Cl(2)(H(2)O)(3)], Am[B(9)O(13)(OH)(4)]·H(2)O, or Cm(2)[B(14)O(20)(OH)(7)(H(2)O)(2)Cl]. These compounds possess three-dimensional network structures where rare earth borate layers are joined together by BO(3) and/or BO(4) groups. There is a shift from 10-coordinate Ln(3+) and An(3+) cations with capped triangular cupola geometries for the early members of both series to 9-coordinate hula-hoop geometries for the later elements. Cm(3+) is anomalous in that it contains both 9- and 10-coordinate metal ions. Despite these materials being synthesized under identical conditions, the two series do not parallel one another. Electronic structure calculations with multireference, CASSCF, and density functional theory (DFT) methods reveal the An 5f orbitals to be localized and predominately uninvolved in bonding. For the Pu(III) borates, a Pu 6p orbital is observed with delocalized electron density on basal oxygen atoms contrasting the Am(III) and Cm(III) borates, where a basal O 2p orbital delocalizes to the An 6d orbital. The electronic structure of the Ce(III) borate is similar to the Pu(III) complexes in that the Ce 4f orbital is localized and noninteracting, but the Ce 5p orbital shows no interaction with the coordinating ligands. Natural bond orbital and natural population analyses at the DFT level illustrate distinctive larger Pu 5f atomic occupancy relative to Am and Cm 5f, as well as unique involvement and occupancy of the An 6d orbitals.     

Extraction of trivalent lanthanides and actinides by primary amines

Extraction of trivalent lanthanides and actinides by primary amines from nitric acid solution in presence of potassium phosphotungstate (K₁₀P₂W₁₇O₆₁) has been investigated. The effect of nitric acid, potassium phosphotungstate and extractant concentrations, of the organic solvents and the length of primary amine alkyl chain has been studied. Primary amines in chloroform can be used for separtion of lanthanides and actinides and their group isolation.     

Separation of trivalent actinides from lanthanides by solvent extraction

A method is presented for separating the trivalent actinides, mainly Am and Cm, from trivalent lanthanides by the use of only two solvent extractants. The first solvent removes the heavy lanthanides, leaving the Am, Cm and the lighterlanthanides; the second removes the Am and Cm. Because additional complexing agents are not required, waste-disposal and corrosion problems are reduced. Overall separation factors may be as high as several thousand for the separation of Am and Cm from lanthanides in the fission waste products from reactor fuel processing.     

Synergistic extraction of trivalent actinides and lanthanides using macrocyclic compounds

The combination of lipophilic macrocyclic oxygen donors with the extractant thenoyltrifluoroacetone /HTTA/ has been shown to have a significant synergistic effect on the extractions of trivalent actinides and lanthanides. The results show that the nitrogen containing cryptand /222BB/ is a more effective synergist than the crown ether compound /15-C-5/ with only oxygen donors.     

The extraction of trivalent actinides and lanthanides by a novel unsymmetrical diglycolamide

Journal of Radioanalytical and Nuclear Chemistry - N,N′-dioctyl-N,N′-di-dodecyl-3-oxapentane-1,5-diamide ((DdO)2DGA) is a novel unsymmetrical diglycolamide. Herein, we analyzed the...     

On the mechanism of extraction of trivalent actinides and lanthanides with alkylamine hydrochlorides

The method to study the mechanism of actinides (III) and lanthanides (III) liquid-liquid amine extraction from chloride media has been suggested. The technique is based on the determination of distribution coefficients for extraction of these elements from mixed salting-out agent solutions with common anion. Distribution coefficients were found to be independent of mean ion activity of lithium cation at constant water activity, when extraction of trace amounts of Eu (III) and Cm(III) by tri-n-octylammonium hydrochloride from mixed LiCl−CaCl₂ solutions occurred. It has been concluded that lithium cation does not enter into the complexed extracted.     

Extraction of trivalent actinides and lanthanides by tertiary and quaternary amines from concentrated chloride solutions

Extraction of some trivalent actinides and lanthanides from 11.9 M LiCl (pH 2.0) by some primary, secondary, tertiary and quaternary amines in xylene has been studied. Negligible extraction of the metal ions was found with primary and secondary amines whereas they are appreciably extracted with tertiary and quaternary amines, the trivalent actinides always being extracted to a greater extent. The separation factors Kd An(III)/Kd Ln(III) for several trivalent actinides with respect to Eu(III) and Tm(III) are found to be much greater when tertiary amines are used as extractants compared to when quaternary amines are used which has been ascribed to the extraction of higher chloro complexes of the metal ions by tertiary amines. Absorption spectra of Am(III) and Nd(III) extracted into the long chain amines from 11.0 M LiCl (pH 2.0) indicate that octahedral hexachloro complexes are present in the tertiary amine extracts whereas lower complexes are predominantly extracted by the quaternary amines leading to the observed lower separation factors for the trivalent actinides with reference to the lanthanides. Possible role of hydrogen bonding in the stabilization of chloro complexes extracted by tertiary amines as well as the extraction of hydrated chloro complexes by the quaternary amines are discussed.     

用于三价锕镧分离的萃取剂的合成与表征

以6,6'-二氰-2,2'-联吡啶为原料,经两步反应,合成了6,6'二(5,6二乙基-1,2,4-三嗪-3-基)-2,2'-联吡啶.第一步改变条件使反应时间由17d缩短到3d,得到的中间体和目标产物经元素分析、IR,1 HNMR和MS等表征确认.此外,对反应机理进行了初步探讨.     

Adsorption behaviors of trivalent actinides and lanthanides on pyridine resin in lithium chloride aqueous solution

The adsorption behaviors of trivalent actinides and lanthanides on pyridine resin in lithium chloride aqueous solution were investigated. The adsorbed amounts of lanthanides and the degree of mutual separation of lanthanides increased with an increase in the concentration of lithium chloride in aqueous solution. The group separation of the trivalent actinides and lanthanides was observed. This separation phenomenon is similar in a hydrochloric acid solution. However, the adsorption behavior of lanthanides in lithium chloride is different from their behavior in a hydrochloric acid solution. This fact shows that the adsorption mechanisms of lanthanides in a lithium chloride aqueous solution and in a hydrochloric acid solution are different; the adsorption mechanisms are attributed to the ion exchange in a hydrochloric acid solution, and to the complex formation with pyridine group in a lithium chloride solution.     

Quasirelativistic f-in-core pseudopotentials and core-polarization potentials for trivalent actinides and lanthanides: molecular test for trifluorides

Calibration studies of actinide and lanthanide trifluorides are reported for actinide and lanthanide scalar-relativistic energy-consistent f-in-core pseudopotentials, respectively, accompanying valence basis sets as well as core-polarization potentials. Results from Hartree–Fock and coupled-cluster singles, doubles, and perturbative triples f-in-core pseudopotential calculations are compared to corresponding data from f-in-valence pseudopotential and all-electron calculations as well as to experimental data. In general, good agreement is observed between the f-in-core and f-in-valence pseudopotential results, whereas due to the lack of experimental data for the actinides only a good agreement of the calculated and experimentally determined bond lengths of the lanthanide systems can be established. Nevertheless, the results indicate that the core-polarization potentials devised here for actinides improve the f-in-core results.     

Group separation of trivalent actinides and lanthanides by tertiary pyridine-type anion-exchange resin embedded in silica beads

The separation of trivalent actinides and lanthanides was studied by using newly developed tertiary pyridine-type anion-exchange resin embedded in silica beads. Chromatographic elution experiments were carried out by using a packed column of the new resin and methanol-hydrochloric acid solution as an effluent. We confirmed that the actinides were eluted well from the elution bands of lanthanides. Actinides and lanthanides were eluted according to the reverse order of their atomic number.     

Liquid-liquid extraction of trivalent actinides and lanthanides with 1-phenyl-3-methyl-4- trifluoroacetyl pyrazolone-5

Extraction of the trivalent actinides Am, Cm and Cf and lanthanides Eu, Tb, Tm and Lu has been studied with 1-phenyl-3-methyl-4-trifluoroacetyl pyrazolone- 5(HPMTFP) in chloroform and benzene. The formation of a self-adduct species M(PMTFP)₃·HPMTFP has been observed with Am, Cm and Eu but only the chelate species M(PMTFP)₃ with Cf, Tb, Tm and Lu. The reasons for the formation of a self-adduct species with lighter actinides and lanthanides and not with the heavier ones of the pyrazolones have been discussed.     

Atomic interaction parameters for lanthanides and actinides

A correlation between the Mie-Lennard-Jones interatomic potential and the position of the element in the Periodic Table is used to correct the parameters for lanthanides and to estimate the parameters of the interatomic potential of promethium (Pm-61) for two structures. From the similarity in the double periodicity for the lanthanides and actinides, the minimum coordinates of the interatomic potential r _o are estimated for the elements from curium (Cm-96) through dubnium (Db-105). From the fact that, for Z _a > 60, r _o decreases with increasing atomic number Z _a for the elements of one column, r _o for roentgenium (Rg-111) is estimated. The corrected parameters of the potential are predicted for the elements from francium (Fr-87) through dubnium (Db-105). From the derived parameters of the interatomic potential, the Debye temperatures and the Grüneisen parameters are calculated for neptunium (Np-93) and americium (Am-95).     

Sulphate complexing of some trivalent actinides

The sulphate complexing of the trivalent actinides Pu(III), Am(III) and Cm(III) in aqueous solutions was studied by the dinonylnaphthalene sulphonic acid extraction method, at ionic strengths of 1 and 2, at 25°C and the respective stability constant values obtained are reported. The extraction of the actinide ions from sulphuric acid into amines indicated the existence of their anionic sulphate complex species.     

Phosphate ester hydrolysis by hydroxo complexes of trivalent lanthanides stabilized by 4-imidazolecarboxylate

The anion of 4-imidazolecarboxylic acid (HL) stabilizes hydroxo complexes of trivalent lanthanides of the type ML(OH)+ (M = La, Pr) and M2L(n)(OH)(6-n) (M = La, n = 2; M = Pr, n = 2, 3; M = Nd, Eu, Dy, n = 1-3). Compositions and stability constants of the complexes have been determined by potentiometric titrations. Spectrophotometric and (1)H NMR titrations with Nd(III) support the reaction model for the formation of hydroxo complexes proposed on the basis of potentiometric results. Kinetics of the hydrolysis of two phosphate diesters, bis(4-nitrophenyl) phosphate (BNPP) and 2-hydroxypropyl 4-nitrophenyl phosphate (HPNPP), and a triester, 4-nitrophenyl diphenyl phosphate (NPDPP), in the presence of hydroxo complexes of five lanthanides were studied as a function of pH and metal and ligand concentrations. With all lanthanides and all substrates, complexes with the smallest n, that is M2L2(OH)4 for La and Pr and M2L(OH)5 for Nd, Eu, and Dy, exhibited the highest catalytic activity. Strong inhibitory effects by simple anions (Cl-, NO3-, (EtO)2PO2-, AcO-) were observed indicating high affinity of neutral hydroxo complexes toward anionic species. The catalytic activity decreased in the order La > Pr > Nd > Eu > Dy for both diester substrates and was practically independent of the nature of cation for a triester substrate. The efficiency of catalysis, expressed as the ratio of the second-order rate constant for the ester cleavage by the hydroxo complex to the second-order rate constant for the alkaline hydrolysis of the respective substrate, varied from ca. 1 for NPDPP to 10(2) for HPNPP and to 10(5) for BNPP. The proposed mechanism of catalytic hydrolysis involves reversible bridging complexation of a phosphodiester to the binuclear active species followed by attack on the phosphoryl group by bridging hydroxide (BNPP) or by the alkoxide group of the deprotonated substrate (HPNPP).     

Simplified speciation and improved phosphodiesterolytic activity of hydroxo complexes of trivalent lanthanides in aqueous DMSO

Potentiometric titrations of La(III), Nd(III), and Eu(III) perchlorates by Me 4N(OH) in 80% vol aq DMSO revealed formation of predominantly mononuclear complexes M(OH)n(3- n) (n = 1, 2, or 3) and a single binuclear complex M2(OH)(5+). Kinetics of the cleavage of two phosphate diesters, bis (4-nitrophenyl) phosphate (BNPP) and 2-hydroxypropyl 4-nitrophenyl phosphate (HPNPP), and a triester, 4-nitrophenyl diethyl phosphate (paraoxon), were studied as a function of metal and Me4N(OH) concentrations in the same medium. Rate of BNPP cleavage is second-order in metal and is proportional to the product of concentrations of M(OH)2(+) and M(OH)3 species. Rate of HPNPP cleavage is proportional to [M(OH)3](3) for La(III) and Nd(III) and to [M(OH)3](2) for Eu(III). Proposed mechanism for BNPP hydrolysis involves formation of M2(OH)5(diester) intermediate followed by intramolecular nucleophilic attack of hydroxide anion on the phosphoryl group of the substrate. Proposed mechanism for HPNPP cleavage involves formation of M3(OH)9(diester)(-) or M2(OH)6(diester)(-) intermediates followed by the general base-assisted intramolecular cyclization of HPNPP. The latter mechanism is supported by observation of the solvent kinetic isotope effect k H/kD = 2.9 for Eu(III) catalyzed HPNPP cleavage. The efficiency of catalysis in 80% DMSO is much higher than in water. The reaction rate observed in the presence of 1 mM metal in neutral solution surpasses the rate of background hydrolysis by a factor of 10(12)-10(13) for BNPP and 10(10) for HPNPP. The increased catalytic activity is attributed principally to the preferable solvation of lanthanide ions by DMSO, which creates an anhydrous microenvironment favorable for reaction in the coordination sphere of the catalyst. The catalytic activity of lanthanides in paraoxon hydrolysis is much lower with the estimated efficiency of catalysis about 10(5) for 1 mM La(III).     

Analytical separations of lanthanides and actinides by capillary electrophoresis

The separation of lanthanide and actinide elements belongs to one of the most challenging tasks of the separation science, due to a great similarity in their physical and chemical properties. The electrophoretic separation can be accomplished in the presence of suitable complex-forming agents, from which alpha-hydroxyisobutyric acid (HIBA) has been used most often. In the most effective capillary electrophoretic mode--capillary zone electrophoresis (CZE)--a complete separation of lanthanide ions can be accomplished within a few minutes. Various electrophoretic methods can be relatively easily adopted for the determinations of individual lanthanide elements in certain kinds of technical materials, concentrates, precursors, etc., where the high speed and low costs of analysis characteristics of capillary electrophoresis (CE) may be advantageously exploited. Electrophoretic techniques may also be employed for speciation studies, especially for examinations of the behavior of actinides in the environment.     

Interaction of granitic biotite with selected lanthanides and actinides

The interaction of granitic biotite with aqueous solutions of La, Nd, Th and U (concentration 10 to 1000 mg·l^-1) was studied using instrumental neutron activation analysis (INAA) and ¹²C-Rutherford backscattering spectroscopy (¹²C-RBS). For comparison, the sorption of La and Nd by granitic feldspar and natural zeolite heulandite was also investigated. The experimental results showed that biotite exhibits higher sorption ability towards La and Nd, (maximum uptake 2.09 and 7.98 mg/g, respectively) than the feldspar and the heulandite. The interaction of biotite with Th is also intense, the metal being preferably concentrated at the near-surface layers of the crystals. This indicates that other sorption mechanisms (adsorption and surface precipitation) than ion-exchange take place at the solid/solution interface. The same phenomenon was also observed in the case of U, although the corresponding metal uptake was found to be considerably lower.     

Stabilization of actinides and lanthanides in high oxidation states

The stabilization of actinides and lanthanides in unusually high oxidation states can be rationalized on the basis of the interplay of crystal-lattice, acid-base, charge, size and redox factors. In this paper we apply arguments based on such influences to selected high-valent actinide and/or lanthanide compounds. Two new structural studies of the incorporation of f-element cations into the important perovskite structure are briefly discussed. Recently developed superoxidizer-superacid techniques which hold great promise for synthesis of new high-valent f-element fluorides are also mentioned.     

Mixed-ligand chelate extraction of trivalent lanthanides and actinides with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 and dihexyl-N,N-diethylcarbamoylmethyl phosphonate

Mixed-ligand chelate extraction of trivalent lanthanides such as La, Eu and Lu and a trivalent actinide, Am into xylene with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) and dihexyl-N,N-diethylcarbamoylmethylphosphonate (CMP) has been studied by tracertechniques. These trivalent metal ions are found to be extracted from 0.01 mol/dm³ chloroacetate buffer solutions as M(PMBP)₃·HPMBP type self adducts with HPMBP alone and in the presence of CMP as M(PMBP)₃·CMP (where M=La, Eu, Lu and Am) into the organic phase. The equilibrium constants of the above species are deduced by non-linear regression analysis. The synergistic constants of trivalent lanthanides do not increase monotonically with atomic number but have a maximum at Eu and that of Am was found to lie between that of La and Eu.