Pentavalent Uranium Oxide via Reduction of [UO2]2+ Under Hydrothermal Reaction Conditions†

Belai, Nebebech; Frisch, Mark; Ilton, Eugene S.; Ravel, Bruce; Cahill, Christopher L.

doi:10.1021/ic801534m

Cited by 79 publications

(63 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4 , whose structure and spectroscopic details were recently reported by Cahill and co-workers. [8] However, in 1 there are six crystallographically unique uranium sites. Four (2) of these sites yield normal UO 7 pentagonal bipyramids with standard uranyl cores.…”

Section: Resultsmentioning

confidence: 99%

“…[1] As expected, all of the bonds to U(1) in 1 and U(5) in 2 are notably shorter than those found for the U V site in 4 . [8] The remaining five sites also have bond-valence sums consistent with U VI . The high negative charge that this moiety bears is compensated for by coordination of the tetraoxido core to six neighboring uranyl cations as shown in Figure 2 (a, b).…”

Section: General Aspectsmentioning

confidence: 99%

See 1 more Smart Citation

Uranium(VI) Adopts a Tetraoxido Core

Ling

Wang

et al. 2009

Eur J Inorg Chem

View full text Add to dashboard Cite

Section: Resultsmentioning

confidence: 99%

Section: General Aspectsmentioning

confidence: 99%

Uranium(VI) Adopts a Tetraoxido Core

Ling

Wang

et al. 2009

Eur J Inorg Chem

View full text Add to dashboard Cite

“…A U(V)-U(VI) oxyhydroxide phase provided the standard for U(V). The synthesis and characterization of this compound has been described in detail in previous work (Belai et al, 2008). The U(V) component was derived by fitting the mixed valence phase with the U(VI) component (obtained from schoepite) and solving for the U(V) component.…”

Section: X-ray Photoelectron Spectroscopymentioning

confidence: 99%

Comparative dissolution kinetics of biogenic and chemogenic uraninite under oxidizing conditions in the presence of carbonate

Ulrich

Ilton

Veeramani

et al. 2009

Geochimica et Cosmochimica Acta

Self Cite

100

149

View full text Add to dashboard Cite

The long-term stability of biogenic uraninite with respect to oxidative dissolution is pivotal to the success of in situ bioreduction strategies for the subsurface remediation of uranium legacies. Batch and flow-through dissolution experiments were conducted along with spectroscopic analyses to compare biogenic uraninite nanoparticles obtained from Shewanella oneidensis MR-1 and chemogenic UO 2.00 with respect to their equilibrium solubility, dissolution mechanisms, and dissolution kinetics in water of varied oxygen and carbonate concentrations. Both materials exhibited a similar intrinsic solubility of $10 À8 M under reducing conditions. The two materials had comparable dissolution rates under anoxic as well as oxidizing conditions, consistent with structural bulk homology of biogenic and stoichiometric uraninite. Carbonate reversibly promoted uraninite dissolution under both moderately oxidizing and reducing conditions, and the biogenic material yielded higher surface areanormalized dissolution rates than the chemogenic. This difference is in accordance with the higher proportion of U(V) detected on the biogenic uraninite surface by means of X-ray photoelectron spectroscopy. Reasonable sources of a stable U(V)-bearing intermediate phase are discussed. The observed increase of the dissolution rates can be explained by carbonate complexation of U(V) facilitating the detachment of U(V) from the uraninite surface. The fraction of surface-associated U(VI) increased with dissolved oxygen concentration. Simultaneously, X-ray absorption spectra showed conversion of the bulk from UO 2.0 to UO 2+x . In equilibrium with air, combined spectroscopic results support the formation of a near-surface layer of approximate composition UO 2.25 (U 4 O 9 ) coated by an outer layer of U(VI). This result is in accordance with flowthrough dissolution experiments that indicate control of the dissolution rate of surface-oxidized uraninite by the solubility of metaschoepite under the tested conditions. Although U(V) has been observed in electrochemical studies on the dissolution of spent nuclear fuel, this is the first investigation that demonstrates the formation of a stable U(V) intermediate phase on the surface of submicron-sized uraninite particles suspended in aqueous solutions.

show abstract

“…The presence of mixedvalent U V /U VI systems has been reported in few naturally occurring oxide minerals [28] and in rare examples of oxide compounds obtained under hydrothermal conditions. [29][30][31] The first example of mixed-valent Np V /Np VI cation-cation complex was isolated only very recently. [5] Temperature-dependent magnetic data were collected in the temperature range 2-300 K. At 300 K, 4 displays an effective magnetic moment of 1.96 m B per uranium ion, which is lower that the theoretical value calculated for the free f 1 ion in the L-S coupling scheme (m eff = 2.54 m B ), but within the range of values reported for U V compounds.…”

mentioning

confidence: 99%

Stable Pentavalent Uranyl Species and Selective Assembly of a Polymetallic Mixed‐Valent Uranyl Complex by Cation–Cation Interactions

et al. 2009

View full text Add to dashboard Cite

Cation-cation interactions are a key feature of actinide chemistry. These interactions can be used in two areas that currently attract great interest, namely the expansion of felement supramolecular chemistry and the enhancement of magnetic interactions in actinide compounds. [1][2][3][4][5][6][7][8][9][10][11][12] Moreover, oligomeric cation-cation species that present mutually coordinated actinyl ions are likely to play a crucial role in nuclear waste reprocessing and in the migration of radioactive actinides in the environment. [1] Cation-cation interactions are known to be important in neptunyl(V) structural chemistry, [13] but are more rarely found in uranyl(VI) compounds because of the lower basicity of the UO 2 2+ oxygen atoms. Dimeric compounds formed through the mutual binding of pentavalent uranyl(V) ions have been proposed as intermediates in the disproportionation of pentavalent uranyl ions to UO 2 2+ and U IV species.[14]As a result, bulky ligands have been used in the past few years to disfavor cation-cation interactions and allow the synthesis of rare UO 2 + complexes, [15][16][17][18][19][20][21] which have been the subject of two recent reviews.[ [8] The presence of antiferromagnetic coupling between the oxo-bridged uranium centers was unambiguously demonstrated for the dimetallic complex but is less evident for the tetrametallic complex. [8] The decomposition of these polymetallic complexes of pentavalent uranyl ions to UO 2 2+ and U IV species starts rapidly after dissolution in organic solvents and is accelerated by traces of water. From these reactivity studies, it occurred to us that the stability of these polymeric systems could possibly be modulated by fine-tuning the electronic and steric properties of the ligand and coordinating cation. Herein, we report the first example of a UO 2 + ···UO 2 + complex that is highly stable in organic solvents and, significantly, is stable toward hydrolysis. We also describe the selective synthesis and the structure of the first mixed-valent UO 2 + ···UO 2 2+ molecular complex, which provides a rare example of functionalization of the U VI =O group. [20,22] By breaking away from the current trend of using steric bulk to prevent dimer formation and the associated disproportionation of UO 2 + complexes, we show that the non-bulky Schiff base ligand salen 2À (N,N'-bis(salicylidene)ethylenediamine) can stabilize pentavalent uranyl ions through the formation of a highly stable cation-cation complex. Moreover, we demonstrate that the resulting tetrameric uranyl(V) complex exhibits unambiguous antiferromagnetic coupling between the uranium centers.The reaction of the recently reported UO 2 + complex [(UO 2 Py 5 )(KI 2 Py 2 )] n (2; Py = pyridine) [23] with salenK 2 in pyridine led to the formation of the complex of pentavalent uranyl 3 as a violet powder that was insoluble in pyridine. The elemental analysis of 3 indicates the presence of a complex of general formula [(UO 2 )(salen)K(Py)]·1.4 KI, which most likely has a solid-state polymeric structure. Compound ...

show abstract

Pentavalent Uranium Oxide via Reduction of [UO₂]²⁺ Under Hydrothermal Reaction Conditions^†

Cited by 79 publications

References 54 publications

Uranium(VI) Adopts a Tetraoxido Core

Uranium(VI) Adopts a Tetraoxido Core

Comparative dissolution kinetics of biogenic and chemogenic uraninite under oxidizing conditions in the presence of carbonate

Stable Pentavalent Uranyl Species and Selective Assembly of a Polymetallic Mixed‐Valent Uranyl Complex by Cation–Cation Interactions

Contact Info

Product

Resources

About