An EXAFS study of uranyl ion in solution and sorbed onto silica and montmorillonite clay colloids

Dent, Andrew J.; Ramsay, J.D.F.; Swanton, S.W.

doi:10.1016/0021-9797(92)90267-p

Cited by 193 publications

(153 citation statements)

References 35 publications

Supporting

Mentioning

133

Contrasting

Unclassified

Order By: Relevance

“…Work by Vachet and Callahan [14] has suggested that the nitrate anion, within gas-phase transition metal complexes, is primarily a bidentate ligand. The acceptance of three additional ligands by the uranyl-nitrate ion pair is consistent with a hypothesis that ESI produces a gasphase complex with a pentagonal bipyramidal conformation reminiscent of the structure of uranyl complexes in the solution phase [5][6][7][8][9][10][11]. The fact that the uranylhydroxide containing complex ion, as generated by ESI, also incorporated a maximum of 3 additional H 2 O ligands is therefore interesting.…”

Section: Discussionsupporting

confidence: 76%

“…The solution chemistry of uranium is dominated by the uranyl dication, UO 2 2ϩ , which is known to form complexes with a range of ligands [1]. Specific interaction with solvent will significantly influence the physico-chemical behavior of the uranyl ion and its complexes, and this has motivated investigations of complex composition and stability using infrared spectroscopy and extended X-ray absorption fine structure [5][6][7][8][9][10][11]. Unfortunately, explicit control over the interactions of solvent and nonsolvent ligands with the uranyl ion is difficult, which makes the study of species-dependent uranium behavior complicated.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Elucidation of the collision induced dissociation pathways of water and alcohol coordinated complexes containing the uranyl cation

Stipdonk

Anbalagan

Chien

et al. 2003

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

Multiple-stage tandem mass spectrometry was used to characterize the dissociation pathways for complexes composed of (1) the uranyl ion, (2) nitrate or hydroxide, and (3) water or alcohol. The complex ions were derived from electrospray ionization (ESI) ϩ . The abundance of the species was greater than expected based on previous experimental measurements of the (slow) hydration rate for UO 2 ϩ when stored in the ion trap. To account for the production of the hydrated product, a reductive elimination reaction involving reactive collisions with water in the ion trap is proposed. T he speciation and reactivity of uranium is a topic of sustained interest because species-dependent chemistry [1] controls processes ranging from nuclear fuel processing [2] to mobility and fate in the geologic subsurface [3,4]. The solution chemistry of uranium is dominated by the uranyl dication, UO 2 2ϩ , which is known to form complexes with a range of ligands [1]. Specific interaction with solvent will significantly influence the physico-chemical behavior of the uranyl ion and its complexes, and this has motivated investigations of complex composition and stability using infrared spectroscopy and extended X-ray absorption fine structure [5][6][7][8][9][10][11]. Unfortunately, explicit control over the interactions of solvent and nonsolvent ligands with the uranyl ion is difficult, which makes the study of species-dependent uranium behavior complicated. To gain a better understanding of the intrinsic interactions between different uranyl species and solvent, we have begun an investigation of uranyl-anion complexes in the gas phase using ion-trap mass spectrometry (IT-MS). Several recent reports have demonstrated that intrinsic metal and metal complex chemistry can be investigated by the (controlled) addition of reagent gas to an ion trap [12][13][14][15][16][17][18][19][20][21][22], or by way of the presence of H 2 O and other small molecule contaminants within the He bath gas used to collisionally cool ions and improve trapping efficiency [23][24][25]. The reactions of uranium ions in the gas phase have been the subject of several earlier investigations. Studies by , and by Schwarz and coworkers [30] have probed the reactions between U ϩ and UO ϩ and organic compounds such as alkanes and alcohols. Armentrout and Beauchamp [31] investigated the oxidation of U ϩ using small molecules such as O 2 , CO, CO 2 , COS, and

show abstract

Section: Discussionsupporting

confidence: 76%

mentioning

confidence: 99%

Elucidation of the collision induced dissociation pathways of water and alcohol coordinated complexes containing the uranyl cation

Stipdonk

Anbalagan

Chien

et al. 2003

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

show abstract

“…In aqueous solutions, a hydration number of 5 is reported for the (U02)2+ ion [40] although a coordination number of 6 is expected for carbonate or other bidentate ligands [23,37]. The coordination geometry observed for the uranyl ion in the clay samples examined here is consistent with that observed in the aqueous phase, and in other studies of uranyl-clay complexes.…”

Section: Powder X-ray Diffractionsupporting

confidence: 84%

Speciation of uranium in surface-modified, hydrothermally treated, (UO{sub 2}){sup 2+}-exchanged smectite clays

Giaquinta¹,

Soderholm²,

Yuchs³

et al. 1997

View full text Add to dashboard Cite

I .--X-ray absorption spectroscopy (XAS) is used to determine the uranium speciation in exchanged and surface-modified clays. The XAS data from uranyl-loaded bentonite clay are compared with those obtained after the particle surfaces have been coated with alkylsilanes. These silane films, which render the surface of the clay hydrophobic, are added in order to minimize the ability of external water to exchange with the water in the clay interlayer, thereby decreasing the release rate of the exchangeduranium species. Mild hydrothermal conditions are used in an effort to mimic potential geologic conditions that may occur during long-term radioactive waste storage. The XAS spectra indicate that the uranyl monomer species remain unchanged in most samples, except in those samples that were both coated with an alkylsilane and hydrothermally treated. When the clay was coated with an organic film, formed by the acidic deposition of octadecyltrimethoxysilane, hydrothermal treatment results in the formation of aggregated uranium species in which the .. , 2 uranium is reduced from UvI to UIV. The implications of this reduction to efforts in environmental remediation are discussed.

show abstract

“…X-ray absorption fine structure spectroscopy (XAFSS) and X-ray photoelectron spectroscopy (XPS) have been used to provide information on the U oxidation state and the coordination environment of UO 2 2+ in solids (e.g., sediments) and at the solid-water interface (Table 1) [53,54,55]. Both in water and at the solid-water interface, the formation of multinuclear uranyl complexes may be detected as precursors to solid phase formation [56,57]. Fluorescent XAFSS is used for solids containing lower U concentrations, because of its higher sensitivity to U. Photothermal (photoacoustic) spectrometry (Table 1) has been used to effectively characterize the speciation of UO 2 2+ in solids, particularly amorphous phases [58].…”

Section: Sedimentmentioning

confidence: 99%

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

Markich

2002

The Scientific World JOURNAL

203

142

View full text Add to dashboard Cite

The speciation of uranium (U) in relation to its bioavailability is reviewed for surface waters (fresh-and seawater) and their sediments. A summary of available analytical and modeling techniques for determining U speciation is also presented. U(VI) is the major form of U in oxic surface waters, while U(IV) is the major form in anoxic waters. The bioavailability of U (i.e., its ability to bind to or traverse the cell surface of an organism) is dependent on its speciation, or physicochemical form. U occurs in surface waters in a variety of physicochemical forms, including the free metal ion (U 4+ or UO 2 2+ ) and complexes with inorganic ligands (e.g., uranyl carbonate or uranyl phosphate), and humic substances (HS) (e.g., uranyl fulvate) in dissolved, colloidal, and/or particulate forms. Although the relationship between U speciation and bioavailability is complex, there is reasonable evidence to indicate that UO 2 2+ and UO 2 OH + are the major forms of U(VI) available to organisms, rather than U in strong complexes (e.g., uranyl fulvate) or adsorbed to colloidal and/or particulate matter. U(VI) complexes with inorganic ligands (e.g., carbonate or phosphate) and HS apparently reduce the bioavailability of U by reducing the activity of UO 2 2+ and UO 2 OH + . The majority of studies have used the results from thermodynamic speciation modeling to support these conclusions. Time-resolved laser-induced fluorescence spectroscopy is the only analytical technique able to directly determine specific U species, but is limited in use to freshwaters of low pH and ionic strength. Nearly all of the available information relating the speciation of U to its bioavailability has been derived using simple, chemically defined experimental freshwaters, rather than natural waters. No data are available for estuarine or seawater. Furthermore, there are no available data on the relationship between U speciation and bioavailability in sediments. An understanding of this relationship has been hindered due to the lack of direct quantitative U speciation techniques for particulate phases. More robust analytical techniques for determining the speciation of U in natural surface waters are needed before the relationship between U speciation and bioavailability can be clarified.

show abstract

An EXAFS study of uranyl ion in solution and sorbed onto silica and montmorillonite clay colloids

Cited by 193 publications

References 35 publications

Elucidation of the collision induced dissociation pathways of water and alcohol coordinated complexes containing the uranyl cation

Elucidation of the collision induced dissociation pathways of water and alcohol coordinated complexes containing the uranyl cation

Speciation of uranium in surface-modified, hydrothermally treated, (UO{sub 2}){sup 2+}-exchanged smectite clays

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

Contact Info

Product

Resources

About