Understanding the unique paradigm in the extraction of tri- and tetravalent actinide/lanthanide ions by a diglycolamide-functionalized dendrimer in RTIL medium

A dendrimer of tris(2-aminoethyl)amine (TREN), containing six diglycolamide (DGA) pendent arms (TREN-G1-DGA) was evaluated for the extraction of different actinides and Eu3+ in a methylimidazolium-based room temperature ionic liquid (RTIL;...

Properties of the tetravalent actinide series in aqueous phase from a microscopic simulation self-consistent engine

Classical molecular dynamics hydration study for the An(iv) series performed using an automated iterative ab initio based engine.

Synthesis and reactivity of low-valent uranium and neptunium complexes

Chapter 1 reports the synthesis and characterization of U(IV) and Np(IV) selenium bis(phenolate) complexes. The reaction of the U(IV) complex with half an equivalent of p-benzoquinone results in the formation of a U(V)--U(V) species with a bridging reduced quinone. This represents a rare example of high-valent uranium chemistry as well as a rare example of a neptunium aryloxide complex. In Chapters 2 and 3 the synthesis and characterization of a rare U(III) hydrocarbyl complex, U[[eta]4-Me2NC(H)C6H5]3, and the first structurally characterized transuranic hydrocarbyl complex, Np[[eta]4-Me2NC(H)C6H5]3, complex, has been generated with four equivalents of the K[Me2NC(H)C6H5] ligand. In the analogous Th(IV) reaction, C-H bond activation of a methyl group of one dimethylamine was observed yielding Th[[eta]4-Me2NC(H)C6H5]2[[eta]5-(CH2)MeNC(H)C6H5] with a dianionic DMBA ligand. The utility of these complexes as starting materials has been analyzed using a bulky dithiocarboxylate ligand to yield tetravalent actinide species for U and Th but Np maintains the trivalent oxidation state. Chapter 4 describes the on-going synthesis and reactivity of Np(OAr)3 (Ar = 2,6-di-tert-butylphenoxide) utilizing Np[[eta]4-Me2NC(H)C6H5]3 as a Np(III) starting material. The coordination and oxidation chemistry is explored with [nBu4N]N3, (C6H5CO)2O2 and Ph2S2 resulting in a bridged Np(III)/Np(III) azide complex with an outer sphere nBu4N and Np(IV) species, respectively.

Self-Propagating Synthesis and Characterization Studies of Gd-Bearing Hf-Zirconolite Ceramic Waste Forms

Synroc is recognized as the second-generation waste matrice for nuclear waste disposal. Zirconolite is one of the most durable Synroc minerals. In this study, Gd and Hf were selected as the surrogates of trivalent and tetravalent actinide nuclides. Gd-bearing Hf-zirconolite (Ca1−xHf1−xGd2xTi2O7) ceramic waste forms were rapidly synthesized from a self-propagating technique using CuO as the oxidant. The results indicate that Gd can concurrently replace the Ca and Hf sites. However, Gd2O3 could not completely be incorporated into the lattice structure of zirconolite when the x value is higher than 0.8. The aqueous durability of selected Gd-Hf codoped sample (Hf-Gd-0.6) was tested, where the 42 days normalized leaching rates (LRi) of Ca, Cu, Gd and Hf are measured to be 1.57, 0.13, 4.72 × 10−7 and 1.59 × 10−8 g·m−2·d−1.