Solution and Solid-State Structural Chemistry of Actinide Hydrates and Their Hydrolysis and Condensation Products

Knope, Karah E.; Soderholm, L.

doi:10.1021/cr300212f

Cited by 324 publications

(439 citation statements)

References 296 publications

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“…This condensation process can occur through olation (hydroxo bridge) or oxolation (oxo bridge) reactions. [5] In nature, the chemistry and the constituent of uranium complexes is highly dependable on the immediate environment constitution. In soils, the decomposition of organic matter produces an infinite library of organic complexants that can modulate the chemistry of actinides.…”

Section: +mentioning

confidence: 99%

“…[4,[10][11][12] So far, the study dedicated to the crystallization of tetravalent uranium-based carboxylate complexes remains relatively rare. [4,5,7] This lack of interest is mainly explained by the difficulty in avoiding the oxidation process and the formation of hexavalent uranium. In spite of the instability of the tetravalent uranium form, this cation naturally occurs thanks to the specific environment combining reductive species and anaerobic biotic conditions.…”

Section: +mentioning

confidence: 99%

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Solvothermal Synthesis of Tetravalent Uranium with Isophthalate or Pyromellitate Ligands

et al. 2015

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Three new coordination polymers bearing tetravalent uranium have been isolated with the O‐donor ligands such as isophthalate (1,3‐bdc) or pyromellitate (btec). The compounds 1 and 3 have been solvothermaly synthesized in N,N‐dimethylformamide (DMF). The crystal structure of U(1,3‐bdc)2(DMF) (1) is built up from discrete tricapped trigonal‐primastic UO9 units, for which one carbonyl oxygen atom from DMF is bound to uranium. The connection of the UO9 units with the isophthalate linkers occurs in a chelating and bidentate fashion and gives rise to the formation of a 3D framework, delimiting narrow channels running along the [101] direction. Upon heating, the DMF molecules are removed, generating the second phase U(1,3‐bdc)2 (2) compound, closely related to 1. Indeed, the coordination environment of uranium is reduced to eight with a distorted square‐antiprismatic geometry. This transition induces the relative shrinkage of the network (ΔV = 23 %). The structure of the compound U(btec)(DMF)2 (3) also exhibits a 3D framework composed of an isolated bicapped square‐antiprismatic UO10 unit, for which two carbonyl oxygen atoms from DMF are bonded to uranium. Pyromellitate ensures the connection of the UO10 units through the carboxylate arms in a chelating mode. This results in the formation of a network with diamond‐shaped channels, developed along the c axis and encapsulating the DMF molecules. In contrast to 1, no stable phase is observed upon removing the DMF species by heating.

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Section: +mentioning

confidence: 99%

Section: +mentioning

confidence: 99%

Solvothermal Synthesis of Tetravalent Uranium with Isophthalate or Pyromellitate Ligands

et al. 2015

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“…Atomic force microscopy confirms that plutonium is present as discrete nanoparticles. Thorium's tendency to hydrolyze and polymerize is less pronounced than plutonium's (Knope and Soderholm, 2012), thus it is expected that Th only begins to polymerize at higher interfacial concentrations. Therefore the central question appears to be to understand what factors control the interfacial Th concentration and consequently allow it to become sufficiently high for nanoparticle formation at the interface.…”

Section: Potential Mechanisms For Background Electrolyte Effectsmentioning

confidence: 99%

“…hydrolysis, and subsequent oligomerization. These reactions and their thermodynamics have been studied in great detail (Baes et al, 1958;Brown et al, 1983;Ryan and Rai, 1987;Felmy et al, 1991;Ekberg et al, 2000;Neck et al, 2002;Wilson et al, 2007;Rand et al, 2008;Walther et al, 2008;Knope et al, 2011;Knope and Soderholm, 2012), and it has become increasingly clear that condensation reactions can significantly impact Th(IV) solution chemistry, even at relatively low pH and low Th concentration.…”

Section: Introductionmentioning

confidence: 99%

Effects of the background electrolyte on Th(IV) sorption to muscovite mica

Schmidt

Hellebrandt

Knope

et al. 2015

Geochimica et Cosmochimica Acta

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The adsorption of tetravalent thorium on the muscovite mica (0 0 1) basal plane was studied by X-ray crystal truncation rod (CTR) and resonant anomalous X-ray reflectivity (RAXR) measurements and alpha spectrometry in the presence of perchlorate background electrolytes LiClO 4 , NaClO 4 , and KClO 4 ([Th(IV)] = 0.1 mM, I = 0.1 M or 0.01 M, pH = 3.3 ± 0.3). RAXR data directly reveal a strong influence of the background electrolyte on the actinide sorption. No significant Th adsorption was observed in 0.1 M NaClO 4 , i.e., the Th coverage h(Th), the number of Th per unit cell area of the muscovite surface (A UC = 46.72 Å 2 ), was 60.01 Th/A UC , whereas limited uptake (h(Th) $ 0.04 Th/A UC ) was detected at a lower ionic strength (I = 0.01 M). These results are in stark contrast to the behavior of Th in 0.1 M NaCl which showed a coverage of 0.4 Th/A UC (Schmidt et al., 2012a). Th uptake was also influenced by the electrolyte cation. Weak adsorption was observed in 0.1 M KClO 4 (h(Th) $ 0.07 Th/A UC ) similar to the results in NaClO 4 at lower ionic strength. In contrast, strong adsorption was found in 0.1 M LiClO 4 , with h(Th) = 4.9 Th/A UC , a $10-fold increase compared with that previously reported in NaCl. These differences are confirmed independently by ex situ alpha spectrometry, which shows no measurable Th coverage in 0.1 M NaClO 4 background in contrast to a large coverage of 1.6 Th/A UC in 0.1 M LiClO 4 . Alpha spectrometry cannot be obtained in situ, but sample preparation requires several washing steps that may affect Th(IV) sorption, RAXR, however, is considered to reflect the in situ sorption structure. The CTR/RAXR analyses of Th-LiClO 4 show the sorption structure consisting of Th species that are broadly distributed, centered at heights of 4.1 Å and 29 Å distance from the interface. Neither the very large distribution height of the second species nor the high coverage can be explained with (hydrated) ionic adsorption, suggesting that the enhanced uptake is presumably due to the formation and sorption of Th nanoparticles.

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“…Detailed information about the local structure around the atoms of a specific element can be obtained from X-ray absorption fine structure (XAFS). Numerous XAFS studies of the coordination structure of uranium complexes have been conducted and reviewed [2][3][4][5][6][7]. The technique enables the identification of the valence states of uranium during the redox reactions from the X-ray absorption near-edge structure (XANES [8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

An in-situ X-ray absorption spectroelectrochemical study of the electroreduction of uranium ions in HCl, HNO₃, and Na₂CO₃ solutions

et al. 2015

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Solution and Solid-State Structural Chemistry of Actinide Hydrates and Their Hydrolysis and Condensation Products

Cited by 324 publications

References 296 publications

Solvothermal Synthesis of Tetravalent Uranium with Isophthalate or Pyromellitate Ligands

Solvothermal Synthesis of Tetravalent Uranium with Isophthalate or Pyromellitate Ligands

Effects of the background electrolyte on Th(IV) sorption to muscovite mica

An in-situ X-ray absorption spectroelectrochemical study of the electroreduction of uranium ions in HCl, HNO₃, and Na₂CO₃ solutions

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Solution and Solid-State Structural Chemistry of Actinide Hydrates and Their Hydrolysis and Condensation Products

Cited by 324 publications

References 296 publications

Solvothermal Synthesis of Tetravalent Uranium with Isophthalate or Pyromellitate Ligands

Solvothermal Synthesis of Tetravalent Uranium with Isophthalate or Pyromellitate Ligands

Effects of the background electrolyte on Th(IV) sorption to muscovite mica

An in-situ X-ray absorption spectroelectrochemical study of the electroreduction of uranium ions in HCl, HNO3, and Na2CO3 solutions

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An in-situ X-ray absorption spectroelectrochemical study of the electroreduction of uranium ions in HCl, HNO₃, and Na₂CO₃ solutions