On the Structure of the Hydrolysis Products of Thorium.

Johansson, Georg; Kierkegaard, Peder; Fontell, Krister; Larsen, Charles; Pedersen, C. Th.; Rosén, Ulf

doi:10.3891/acta.chem.scand.22-0399

Cited by 31 publications

(23 citation statements)

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“…Overall, it is clear that condensation of hydrolysed Th plays an important role in its solution chemistry, particularly with the observed presence of dissolved polynuclear species even at relatively low concentrations and acidic pH. Complementary solid-state studies provide insight into the stable structures of Th hydroxo-bridged dimers (Johansson, 1968;Wilson et al, 2007b), tetramers (Harrowfield et al, 1991), and hexamers (Takao et al, 2009;Knope et al, 2011). This chemistry must be considered when describing the sorption behavior of Th(IV) onto surfaces in contact with these solutions.…”

Section: Introductionmentioning

confidence: 97%

Sorption of tetravalent thorium on muscovite

Schmidt

Lee

Wilson

et al. 2012

Geochimica et Cosmochimica Acta

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Adsorption of tetravalent thorium to the (0 0 1) basal surface of the phyllosilicate muscovite from an aqueous solution (1 Â 10 À4 mol/L Th(IV) in 1 Â 10 À1 mol/L NaCl, pH = 3.2) was studied by crystal truncation rod (CTR) and resonant anomalous X-ray reflectivity (RAXR) measurements. Th uptake to the muscovite surface from solutions with total Th concentrations [Th] tot = 1 Â 10 À6 -4.88 Â 10 À3 mol/L and 1 Â 10 À1 mol/L NaCl, pH = 3.2 was quantified by alpha-spectrometry. The uptake measurements showed that Th adsorption to the muscovite surface follows a Langmuir isotherm with an apparent adsorption constant K app = 2 Â 10 4 L/mol up to [Th] tot = 1.02 Â 10 À3 mol/L. The CTR and RAXR results identified one dominant Th species with a very broad distribution centered $10 Å above the surface, in agreement with strongly hydrated extended outer sphere sorption. The findings indicate that the large energy of hydration (DG hyd = À5815 kJ/mol (Marcus, 1991)) for the small and highly-charged Th 4+ cation is a controlling parameter in its surface speciation. The surface occupancy (0.4 Th per unit cell area, A UC ) measured by RAXR exceeds the expected level for surface charge compensation by tetravalent Th (0.25 Th/A UC ). However, the radiometric uptake measurements show smaller occupancies (0.21 Th/A UC ) after rinsing by deionized water, indicating a partial removability of sorbed thorium. Thorium oligomerization was observed at total Th concentrations [Th] tot P 2.0 Â 10 À3 mol/L in presence of the surface, although solubility studies suggest that Th is soluble under these solution conditions.

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Section: Introductionmentioning

confidence: 97%

Sorption of tetravalent thorium on muscovite

Schmidt

Lee

Wilson

et al. 2012

Geochimica et Cosmochimica Acta

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“…9 Isolated [Th 2 (OH) 2 ] 6+ dimeric units have been reported in both aqueous solution and solid precipitates. 10,11 Similarly, the hardest of the M IV ions stable in aqueous solution, Zr IV and Hf IV , also present as μ 2 OH − oligomers, even under strongly acidic conditions, 6,12−15 and yield predominately dihydroxobridged crystalline precipitates. 16 Contrasting with the apparent olation behaviors of Th IV and the transition metals Zr IV and Hf IV are those of the tetravalent f ions Ce and Pu, both of which have an ionic radius, and hence a charge-to-radius ratio, intermediate to and bounded by Th IV and Hf IV .…”

Section: ■ Introductionmentioning

confidence: 98%

Two Dihydroxo-Bridged Plutonium(IV) Nitrate Dimers and Their Relevance to Trends in Tetravalent Ion Hydrolysis and Condensation

2015

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We report the room temperature synthesis and structural characterization of a μ2-hydroxo-bridged Pu(IV) dimer obtained from an acidic nitric acid solution. The discrete Pu2(OH)2(NO3)6(H2O)4 moiety crystallized with two distinct crystal structures, [Pu2(OH)2(NO3)6(H2O)4]2·11H2O (1) and Pu2(OH)2(NO3)6(H2O)4·2H2O (2), which differ primarily in the number of incorporated water molecules. High-energy X-ray scattering (HEXS) data obtained from the mother liquor showed evidence of a correlation at 3.7(1) Å but only after concentration of the stock solution. This distance is consistent with the dihydroxo-bridged distance of 3.799(1) Å seen in the solid-state structure as well as with the known Pu-Pu distance in PuO2. The structural characterization of a dihydroxo-bridged Pu moiety is discussed in terms of its relevance to the underlying mechanisms of tetravalent metal-ion condensation.

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“…Intrinsic or eigencolloids are another type of colloid particles that tetravalent actinides [6] and Tc(IV) [7] could form. Intrinsic colloids are formed through the oxo-and hydroxo bridge formation between actinide atoms [8,9]. Rothe et al [10] used laser-induced breakdown detection and extended X-ray absorption fine structure (EXAFS) to detect and probe intrinsic colloids that were present in equilibrium with Pu(OH) 4 even at relatively low pH values.…”

Section: Introductionmentioning

confidence: 99%