Molecular and Supramolecular Study of Uranium/Plutonium Liquid-Liquid Extraction with ,-Dialkylamides.

In the context of the separation of uranium and plutonium from spent fuel allowed by -dialkylamides, three regioisomers of -di(2-ethylhexyl) butyramide (DEHBA or ββ) and the diastereopure isomers of -(2-ethylhexyl)--(oct-3-yl)butyramide (EHOBA or αβ) were synthesized to assess their extraction performance and to study the mechanisms at the origin of the differences observed between the stereo- and regioisomers. The -dialkylamides showed differences in extraction, with a greater effect of regio- than stereoisomerism. A mechanistic study at both the molecular and supramolecular scales was initially applied to explain these effects.

Chronicles of plutonium peroxides: spectroscopic characterization of a new peroxo compound of Pu(IV).

Although hydrogen peroxide (HO) has been highly used in nuclear chemistry for more than 75 years, the preparation and literature description of tetravalent actinide peroxides remain surprisingly scarce. A new insight is given in this topic through the synthesis and thorough structural characterization of a new peroxo compound of Pu(IV).

Micrometric drilling of (meta-)studtite square platelets formed by pseudomorphic conversion of UO under high-frequency ultrasound.

Pseudomorphic transformations are related to chemical conversions of materials while conserving their shape and structural features. Structuring ceramic shapes this way can be used to tailor the physico-chemical properties of materials that can benefit particular applications. In the context of spent nuclear fuel storage interacting with radiolysis products, the sonochemical behavior of powdered UO was investigated in dilute aqueous solutions saturated with Ar/(20 %)O (20 °C).

Ultrasonically controlled synthesis of UO colloidal nanoparticles.

Actinide colloids and nanoparticles (NPs) currently constitute a topic of strong interest due to their potential role in advanced nuclear energetics and the environmental migration of radioactivity. A better understanding of the physico-chemical properties of nanoscale actinide oxides requires robust synthesis approaches. In this work, UO NPs were successfully prepared by sonochemistry from U(IV) solutions previously stabilised in a hydrochloric medium (20 kHz, 65 °C, Ar/(10%)CO).

Synthesis and multi-scale properties of PuO nanoparticles: recent advances and open questions.

Due to the increased attention given to actinide nanomaterials, the question of their structure-property relationship is on the spotlight of recent publications. Plutonium oxide (PuO) particularly plays a central role in nuclear energetics and a comprehensive knowledge about its properties when nanosizing is of paramount interest to understand its behaviour in environmental migration schemes but also for the development of advanced nuclear energy systems underway. The element plutonium further stimulates the curiosity of scientists due to the unique physical and chemical properties it exhibits around the periodic table.

First observation of [Pu(OH)O] cluster during the hydrolytic formation of PuO nanoparticles using H/D kinetic isotope effect.

New insights are provided about the formation mechanism of PuO nanoparticles (NPs) by investigating an unprecedented kinetic isotope effect observed during their hydrolytic synthesis in HO or DO and attributed to OH/OD zero point energy difference. The signature of a Pu(IV) oxo-hydroxo hexanuclear cluster, appearing as an important intermediate during the formation of the 2 nm PuO NPs (synchrotron SAXS/XAS), is further revealed indicating that their formation is controlled by H-transfer reactions occurring during hydroxo to oxo-bridge conversions.

Contribution of Molecular Dynamics in pNMR for the Structural Determination of An and An Complexes in Solution.

In this study, we propose to use classical molecular dynamics (MD) coupled with H NMR spectroscopy to study the conformations of different actinyl An (An = U, Np, and Pu) and An (An = Np) complexes with tetra-ethyl dyglicolamide (TEDGA) ligands in order to have a better representation of such complexes in solution. Molecular dynamics simulations showed its effectiveness in interpreting the experiments by the calculation of geometric factors needed for the determination of magnetic properties of these complexes. We demonstrated that different conformations of the An and An complexes with TEDGA exist in solution with different coordination modes, which is experimentally confirmed by H NMR and EXAFS spectroscopies.

Correction: Formation of plutonium(IV) silicate species in very alkaline reactive media.

Correction for 'Formation of plutonium(IV) silicate species in very alkaline reactive media' by Paul Estevenon , , 2021, , 12528-12536, DOI: 10.1039/D1DT02248B.

Characterization of a Hexanuclear Plutonium(IV) Nanostructure in an Acetate Solution via Visible-Near Infrared Absorption Spectroscopy, Extended X-ray Absorption Fine Structure Spectroscopy, and Density Functional Theory.

A new hexanuclear plutonium cluster has been stabilized in aqueous media with acetate ligands. To probe the formation of such a complex structure, visible-near infrared (vis-NIR) absorption spectroscopy, extended X-ray absorption fine structure (EXAFS) spectroscopy, and density functional theory (DFT) were combined. The presence of PuO(OH)(CHCOO) species in solution was first detected by vis-NIR and EXAFS spectroscopy.

Size and structure of hexanuclear plutonium oxo-hydroxo clusters in aqueous solution from synchrotron analysis.

The size and shape of a water-soluble hexanuclear plutonium cluster were probed by combining synchrotron small-angle X-ray scattering (SAXS) and extended X-ray absorption fine structure (EXAFS). A specific setup coupling both techniques and dedicated to radioactive samples on the MARS beamline endstation at Synchrotron SOLEIL is described. The plutonium hexanuclear cores are well stabilized by the 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid ligands and this allows a good evaluation of the setup to probe the very small plutonium core.

X-ray absorption spectroscopy and actinide electrochemistry: a setup dedicated to radioactive samples applied to neptunium chemistry.

A spectroelectrochemical setup has been developed to investigate radioactive elements in small volumes (0.7 to 2 ml) under oxidation-reduction (redox) controlled conditions by X-ray absorption spectroscopy (XAS). The cell design is presented together with in situ XAS measurements performed during neptunium redox reactions.

Formation of plutonium(IV) silicate species in very alkaline reactive media.

Studying the speciation of Pu(IV) in very alkaline and silicate ion rich reactive media allowed identification of the formation of plutonium(IV)-silicate colloidal suspensions which were stable for months. These colloids were stabilized in aqueous solution for pH > 13 and for concentrations around 10 mol L. Successive filtration processes allowed evaluation of their size, which was found to be smaller than 6 nm.

Ultrasonically assisted conversion of uranium trioxide into uranium(vi) intrinsic colloids.

Under oxidizing conditions, the corrosion of spent nuclear fuel may lead to the leaching of radionuclides including soluble uranyl-based species. The speciation of the generated chemical forms is complex and the related potential formation of colloidal species appears surprisingly poorly reported in the literature. Their formation could however contribute significantly to the mobility of radionuclides in the environment.

A 70-Year-Old Mystery in Technetium Chemistry Explained by the New Technetium Polyoxometalate [H O ] [Tc O ] ⋅ 4H O.

[H O ] [Tc O ] ⋅ 4H O [1] was prepared from an aqueous Tc O solution concentrated over anhydrous H SO . [Tc O ] is the first polyanionic species to be reported for Tc. The unit cell contains one centrosymmetric [Tc O ] polyanion as well as hydronium ions and water molecules.

Electrochemical and Spectroscopic Study of Eu and Eu Coordination in the 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide Ionic Liquid.

Separation processes based on room temperature ionic liquids (RTIL) and electrochemical refining are promising strategies for the recovery of lanthanides from primary ores and electronic waste. However, they require the speciation of dissolved elements to be known with accuracy. In the present study, Eu coordination and Eu /Eu electrochemical behavior as a function of water content in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIm][NTf ]) was investigated using UV-visible spectrophotometry, time-resolved laser fluorescence spectroscopy, electrochemistry, and X-ray absorption spectroscopy.

Coordination Structures of Uranium(VI) and Plutonium(IV) in Organic Solutions with Amide Derivatives.

Carbamide and monoamide derivatives are very promising molecules to achieve U(VI) and Pu(IV) extraction and separation from spent nuclear fuels through solvent extraction. Herein, coordination structures of U(VI) and Pu(IV) complexes with carbamide derivatives were characterized using X-ray crystallography as well as infrared, UV-visible, and EXAFS spectroscopies. Coordination structures are compared to those obtained for monoamide derivatives in order to better understand the role of coordination chemistry in extraction properties.

Probing the local structure of nanoscale actinide oxides: a comparison between PuO and ThO nanoparticles rules out PuO hypothesis.

Actinide research at the nanoscale is gaining fundamental interest due to environmental and industrial issues. The knowledge of the local structure and speciation of actinide nanoparticles, which possibly exhibit specific physico-chemical properties in comparison to bulk materials, would help in a better and reliable description of their behaviour and reactivity. Herein, the synthesis and relevant characterization of PuO and ThO nanoparticles displayed as dispersed colloids, nanopowders, or nanostructured oxide powders allow to establish a clear relationship between the size of the nanocrystals constituting these oxides and their corresponding An(iv) local structure investigated by EXAFS spectroscopy.

Formation of CeSiO from cerium(iii) silicate precursors.

Although the preparation of CeSiO4 has been already reported, the formation of pure cerium silicate from aqueous precursors appears as a challenge. An innovative way of synthesis has been identified in this study, allowing the formation of CeSiO4 after hydrothermal treatment starting from Ce(iii) silicate precursors. Among the experimental parameters examined, significant effects were found according to the nature of the precursor and of the reactive media considered, the pH of the reactive media and the temperature of the hydrothermal process.

Probing the existence of uranyl trisulfate structures in the AMEX solvent extraction process.

Knowledge of the complex microstructure in solvent extraction phases is mandatory for a full comprehension of ionic separation. Coupling EXAFS with MD simulations for uranyl extraction in sulfuric media with tertiary amine extractants enabled unravelling of the unprecedented uranyl tri-sulfate structure.

Deciphering the Crystal Structure of a Scarce 1D Polymeric Thorium Peroxo Sulfate.

The preparation and structural characterization of an original Th peroxo sulfate dihydrate, crystallizing at room temperature in the form of stable 1D polymeric microfibres is described. A combination of laboratory and synchrotron techniques allowed solution of the structure of the Th(O )(SO )(H O) compound, which crystallizes in a new structure type in the space group Pna2 of the orthorhombic crystal system. Particularly, the peroxide ligand coordinates to the Th cations in an unusual μ -η :η :η bridging mode, forming an infinite 1D chain decorated with sulfato ligands exhibiting simultaneously monodentate and bidentate coordination modes.

UO structure in solvent extraction phases resolved at molecular and supramolecular scales: a combined molecular dynamics, EXAFS and SWAXS approach.

A new polarizable force field for describing the solvation of the uranyl (UO22+) cation in solvent extraction phases has been developed for molecular dynamics simulations. The validity of the polarizable force field has been established by comparison with EXAFS and SWAXS experiments. This new force field allows for describing both the UO22+ hydration and solvation properties in good agreement with the experiments.

Insight of the Metal-Ligand Interaction in f-Element Complexes by Paramagnetic NMR Spectroscopy.

The magnetic properties of Ln and An complexes formed with dipicolinate ligands have been studied by NMR spectroscopy. To know precisely the geometries of these complexes, a crystallographic study by single-crystal X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) in solution was performed. Several methods to separate the paramagnetic shifts observed in the NMR spectra were applied to these complexes.

The electronic structure of f-element Prussian blue analogs determined by soft X-ray absorption spectroscopy.

In molecular solids derived from Prussian blue, intermetallic charge transfer is fostered through a cyano bridge two metal ions. In this study, isostructural trivalent lanthanide and tetravalent actinide Prussian blue analogs' valence orbitals are probed by soft X-ray absorption measurements.

Structural Characterization of Am(III)- and Pu(III)-DOTA Complexes.

The complexation of 1,4,7,10-tetrazacyclodecane-1,4,7,10-tetraacetic acid (DOTA) ligand with two trivalent actinides (Am and Pu) was investigated by UV-visible spectrophotometry, NMR spectroscopy, and extended X-ray absorption fine structure in conjunction with computational methods. The complexation process of these two cations is similar to what has been previously observed with lanthanides(III) of similar ionic radius. The complexation takes place in different steps and ends with the formation of a (1:1) complex [(An(III)DOTA)(HO)], where the cation is bonded to the nitrogen atoms of the ring, the four carboxylate arms, and a water molecule to complete the coordination sphere.