Treatment of effluents from uranium oxide production

Ladeira, Ana Cláudia Queiroz; Gonçalves, João S. V.; Morais, Carlos A.

doi:10.1080/09593330.2010.488702

Cited by 6 publications

(3 citation statements)

References 5 publications

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“…Uranium fluorides are an important group of materials that are fundamental for uranium separation processes, are potential materials for use in long-term nuclear waste storage, and can play a role in the development of new classes of fuel rod assemblies. − Not surprisingly, the binary uranium fluorides, such as UF 4 and UF 6 , have been extensively investigated and are currently being used in a variety of nuclear processes. − In addition, over 20 ternary inorganic uranium fluorides (other than minerals), such as alkali uranium fluorides and some transition metal uranium fluorides (Na 2 UF 6 , Na 3 UF 7 , K 3 UF 7 , CsU 2 F 9 , AuU 2 F 11 ) have been synthesized, and their structures were reported in the literature. − Surprisingly, only a handful of quaternary uranium-containing fluorides, such as CaLi 2 UF 8 , have been reported. , Typically the U 4+ cations in these structures are found in large coordination environments of UF x ( x = 7, 8, 9) polyhedra that lead to the formation of complex structure types. Remarkably, the total number of transition metal-containing uranium fluorides is very small, considering the importance of uranium as an element.…”

Section: Introductionmentioning

confidence: 99%

Application of a Mild Hydrothermal Approach Containing an in Situ Reduction Step to the Growth of Single Crystals of the Quaternary U(IV)-Containing Fluorides Na₄MU₆F₃₀ (M = Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) Crystal Growth, Structures, and Magnetic Properties

et al. 2014

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A family of rare U(IV)-containing quaternary fluorides, Na4MU6F30 (M = Mn(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+)), was synthesized in single crystal form via a mild hydrothermal technique utilizing an in situ U(VI) to U(IV) reduction step. The modified hydrothermal route is described, and the conditions to obtain single crystals in high yield are detailed. The crystal structures were determined by single crystal X-ray diffraction. The isostructural fluorides crystallize in a new structure type in the trigonal space group P3̅c1. They exhibit a complex three-dimensional crystal structure consisting of corner- and edge-shared UF9 and MF6 polyhedra. The main building block, a U6F30(6-) group, is arranged to create two distinct hexagonal channels, inside which MF6 octahedra and Na(+) cations are located. The copper-containing member of the series, Na4CuU6F30, is unusual in that the Cu(2+) cation exhibits a rare symmetrical coordination environment consisting of six identical Cu-F bond distances, indicating the lack of the expected Jahn-Teller distortion. Magnetic susceptibility measurements of Na4ZnU6F30 yielded an effective magnetic moment of 3.42 μB for the U(4+) (f(2)) cation in the structure. Measurements of the other members containing magnetic transition-metal cations in addition to U(4+), Na4MU6F30 (M = Mn(2+), Co(2+), Ni(2+), and Cu(2+)) yielded total effective magnetic moments of 10.2, 9.84, 8.87, and 8.52 μB for the Mn-, Co-, Ni-, and Cu-containing materials, respectively. No evidence for long-range magnetic ordering was found down to 2 K. Measurements of the magnetization as a function of applied magnetic field at 2 K for Na4MnU6F30 confirmed that the U(4+) magnetic cation exhibits a nonmagnetic singlet ground state at low temperature. Thermal stability measurements and UV-vis diffuse reflectance spectroscopy are also reported.

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Section: Introductionmentioning

confidence: 99%

Application of a Mild Hydrothermal Approach Containing an in Situ Reduction Step to the Growth of Single Crystals of the Quaternary U(IV)-Containing Fluorides Na₄MU₆F₃₀ (M = Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) Crystal Growth, Structures, and Magnetic Properties

et al. 2014

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“…U(IV) containing fluorides are of particular interest among the many uranium containing materials due to their important roles in uranium separation and in the production of uranium oxides that are currently being used in the uranium enrichment process to create nuclear fuel. − Furthermore, investigations of U(IV) in fluoride hosts is of interest because of potential optical properties exhibited by these materials, such as luminescence, that may find use in applications ranging from UV solid-state lasers to visible light emitting phosphors. − …”

Section: Introductionmentioning

confidence: 99%

Mild Hydrothermal Crystal Growth, Structure, and Magnetic Properties of Ternary U(IV) Containing Fluorides: LiUF₅, KU₂F₉, K₇U₆F₃₁, RbUF₅, RbU₂F₉, and RbU₃F₁₃

et al. 2014

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Single crystals of several ternary alkali uranium fluorides, LiUF5, KU2F9, K7U6F31, RbUF5, RbU2F9, and RbU3F13, have been obtained in a mild hydrothermal process using UO2(CH3CO2)2(H2O)2 as the uranium source. Their crystal structures were determined by single crystal X-ray diffraction. The uranium in the starting reagent was successfully reduced from U(6+) to U(4+) in a dilute hydrofluoric acid environment, aided by the presence of a copper salt. All materials exhibit highly complex crystal structures that range from two-dimensional to three-dimensional. The U(4+) cations are found in high (UF8 and UF9) coordination environments. The magnetic susceptibility measurements yielded effective magnetic moments of 3.01-3.83 μB for the U(4+) cations. The temperature dependent magnetic susceptibility measurements confirmed that the U(4+) cation exhibits a nonmagnetic singlet ground state at low temperatures. No long-range magnetic order was observed for any of the above compositions down to 2 K. Optical and thermal behaviors of the fluorides were also investigated.

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“…In contrast to the chemistry of U(VI), which is synonymous with the chemistry of the uranyl UO 2 2+ group and is embodied by typical coordination environments of square-, pentagonal-, or hexagonal bipyramids, the larger U 4+ cation can exhibit larger coordination environments resulting in more complex crystal structures. Also, complex magnetic properties, especially when coupled with other magnetic ions, can be anticipated due to the presence of unpaired electrons in the 5f orbitals of U(IV). − We have focused on investigating a little-explored class of materials, that of the reduced solid-state uranium fluorides, because of their remarkable structural versatility − and important functions in the uranium separation and uranium oxide production processes. − Although a significant number of U(IV) fluorides have been reported, − ,− the majority of such compounds consist of ternary uranium fluorides; in other words, higher-order systems such as quaternary U(IV) fluorides have only rarely been prepared. In fact, only two quaternary compositions have been thoroughly structurally characterized, CaLiUF 8 , and Na 4 MU 6 F 30 (M = Mn 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ ), the latter of which was recently reported by our group.…”

Section: Introductionmentioning

confidence: 99%

Trivalent Cation-Controlled Phase Space of New U(IV) Fluorides, Na₃MU₆F₃₀ (M = Al³⁺, Ga³⁺, Ti³⁺, V³⁺, Cr³⁺, Fe³⁺): Mild Hydrothermal Synthesis Including an in Situ Reduction Step, Structures, Optical, and Magnetic Properties

et al. 2015

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A series of new, complex U(IV) fluorides, namely, Na3MU6F30 (M = Al(3+), Ga(3+), Ti(3+), V(3+), Cr(3+), and Fe(3+)), containing trivalent transition- and main-group metal cations were synthesized via an in situ reduction step of U(VI) to U(IV). Single crystals of the series were grown in high yield under mild hydrothermal conditions and were characterized by single-crystal X-ray diffraction. The reported compounds crystallize in the trigonal space group P3̅c1 and exhibit complex crystal structures with a three-dimensional (3-D) framework composed of corner- and edge-shared UF9 polyhedra. The arrangement of U2F16 dimers forms two types of hexagonal channels, where MF6 polyhedra and sodium atoms are located. The most interesting structural feature is the presence of the 3-D framework that can accommodate various transition-metal ions in low oxidation states, indicating that the framework acts as an excellent host. Trivalent transition metal ions, even reduced Ti(3+) and V(3+), were stabilized by both the rigid framework and by our synthetic conditions. Utilizing ionic radii of transition metal ions, a phase boundary was investigated, suggesting that there exists a size limit for the M site in the crystal structure. The valence state of uranium was studied by U 4f X-ray photoelectron spectroscopy, which confirmed the presence of U(4+). Temperature-dependent magnetic susceptibility measurements yielded effective magnetic moments of 3.50 and 3.35 μB for Na3MU6F30 (M = Al(3+) and Ga(3+)), respectively. For the other compounds, combined effective magnetic moments of 8.93, 9.09, 9.18, and 10.39 μB were obtained for Ti, V, Cr, and Fe members, respectively. In all cases, large negative Weiss constants were observed, which are indicative of the existence of a spin gap in U(4+). Field-dependent magnetic property measurements at 2 K for Na3FeU6F30 demonstrated that U(4+) attains a nonmagnetic singlet ground state at low temperature. Optical and thermal properties were measured and are reported.

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Treatment of effluents from uranium oxide production

Cited by 6 publications

References 5 publications

Application of a Mild Hydrothermal Approach Containing an in Situ Reduction Step to the Growth of Single Crystals of the Quaternary U(IV)-Containing Fluorides Na₄MU₆F₃₀ (M = Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) Crystal Growth, Structures, and Magnetic Properties

Application of a Mild Hydrothermal Approach Containing an in Situ Reduction Step to the Growth of Single Crystals of the Quaternary U(IV)-Containing Fluorides Na₄MU₆F₃₀ (M = Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) Crystal Growth, Structures, and Magnetic Properties

Mild Hydrothermal Crystal Growth, Structure, and Magnetic Properties of Ternary U(IV) Containing Fluorides: LiUF₅, KU₂F₉, K₇U₆F₃₁, RbUF₅, RbU₂F₉, and RbU₃F₁₃

Trivalent Cation-Controlled Phase Space of New U(IV) Fluorides, Na₃MU₆F₃₀ (M = Al³⁺, Ga³⁺, Ti³⁺, V³⁺, Cr³⁺, Fe³⁺): Mild Hydrothermal Synthesis Including an in Situ Reduction Step, Structures, Optical, and Magnetic Properties

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Treatment of effluents from uranium oxide production

Cited by 6 publications

References 5 publications

Application of a Mild Hydrothermal Approach Containing an in Situ Reduction Step to the Growth of Single Crystals of the Quaternary U(IV)-Containing Fluorides Na4MU6F30 (M = Mn2+, Co2+, Ni2+, Cu2+, and Zn2+) Crystal Growth, Structures, and Magnetic Properties

Application of a Mild Hydrothermal Approach Containing an in Situ Reduction Step to the Growth of Single Crystals of the Quaternary U(IV)-Containing Fluorides Na4MU6F30 (M = Mn2+, Co2+, Ni2+, Cu2+, and Zn2+) Crystal Growth, Structures, and Magnetic Properties

Mild Hydrothermal Crystal Growth, Structure, and Magnetic Properties of Ternary U(IV) Containing Fluorides: LiUF5, KU2F9, K7U6F31, RbUF5, RbU2F9, and RbU3F13

Trivalent Cation-Controlled Phase Space of New U(IV) Fluorides, Na3MU6F30 (M = Al3+, Ga3+, Ti3+, V3+, Cr3+, Fe3+): Mild Hydrothermal Synthesis Including an in Situ Reduction Step, Structures, Optical, and Magnetic Properties

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Application of a Mild Hydrothermal Approach Containing an in Situ Reduction Step to the Growth of Single Crystals of the Quaternary U(IV)-Containing Fluorides Na₄MU₆F₃₀ (M = Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) Crystal Growth, Structures, and Magnetic Properties

Application of a Mild Hydrothermal Approach Containing an in Situ Reduction Step to the Growth of Single Crystals of the Quaternary U(IV)-Containing Fluorides Na₄MU₆F₃₀ (M = Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) Crystal Growth, Structures, and Magnetic Properties

Mild Hydrothermal Crystal Growth, Structure, and Magnetic Properties of Ternary U(IV) Containing Fluorides: LiUF₅, KU₂F₉, K₇U₆F₃₁, RbUF₅, RbU₂F₉, and RbU₃F₁₃

Trivalent Cation-Controlled Phase Space of New U(IV) Fluorides, Na₃MU₆F₃₀ (M = Al³⁺, Ga³⁺, Ti³⁺, V³⁺, Cr³⁺, Fe³⁺): Mild Hydrothermal Synthesis Including an in Situ Reduction Step, Structures, Optical, and Magnetic Properties