Actinide Colloids and Particles of Environmental Concern

Walther, Clemens; Denecke, Melissa A.

doi:10.1021/cr300343c

Cited by 145 publications

(129 citation statements)

References 237 publications

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“…Indeed, certain geochemical situations involving colloid-borne forms of tetravalent uranium favor its transport in the ecosystem. [2][3][4] Whatever the oxidation state of the uranium cations, the formation of uranium-water complexes leads to hydrolysis, which involves the deprotonation of coordinated water. Once formed, the hydrolyzed uranium complex can condense to generate large oligomers and precipitate as uranium oxide based nanoparticles or colloids.…”

Section: +mentioning

confidence: 99%

“…[23] In the present contribution, we extended this systematic study to the use of two new carboxylate ligands, such as isophthalic acid (noted 1,3-H 2 bdc) or pyromellitic acid (or 1,2,4,5-benzentetracarboxylic, noted H 4 btec). The reactions of these ligands with uranium tetrachloride in N,N-dimethylformamide under solvothermal conditions gave rise to the formation of two crystallized compounds: U(1,3-bdc) 2 -(DMF) (1) and U(btec)(DMF) 2 (3). Both structures reveal a three-dimensional framework constructed with isolated uranium centers coordinated by DMF molecules.…”

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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“…Recently, researchers indicated that Pu intrinsic colloid was characterized by crystalline structures (Soderholm et al, 2008;Powell et al, 2011;Delegard, 2013;Romanchuk et al, 2013). They called them crystalline nanoparticles rather than polymers, although the term "polymer" was widely used in many reports (Kersting, 2013;Walther and Denecke, 2013;Marsac et al, 2014).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Trace-level plutonium(IV) polymer stability and its transport in coarse-grained granites

et al. 2015

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“…With the revolutionary development of X-ray sources (synchrotrons) and optics such questions can be answered by micro scale resolution spectroscopy and diffraction techniques [7,8,9,10,11]. A recent review emphasizes the relevance of versatile micro-and nanoanalytical techniques for actinide environmental research [12]. Microscopic X-ray fluorescence (µ-XRF) spectroscopy combined with microscopic X-ray diffraction (µ-XRD) is a unique possibility to study these highly heterogeneous rocks [10,13].…”

Section: Introductionmentioning

confidence: 99%

Microscale analysis of metal uptake by argillaceous rocks using positive matrix factorization of microscopic X-ray fluorescence elemental maps

Osán

Kéri

Breitner

et al. 2014

Spectrochimica Acta Part B: Atomic Spectroscopy

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Argillaceous rocks are considered in most European countries as suitable host rock formations for the deep geological disposal of high-level radioactive waste (HLW). The most important chemical characteristic in this respect is their generally strong radionuclide retention property due to the high sorption capacity. Consequently, the physico-chemical parameters of these processes have to be studied in great detail. Synchrotron radiation microscopic X-ray fluorescence (SR µ-XRF) has sufficient sensitivity to study these processes on the microscale without the necessity of the application of radioactive substances. The present study focuses on the interaction between the escaped ions and the host-rock surrounding the planned HLW repository. SR µ-XRF measurements were performed on thin sections subjected to sorption experiments using 5 µm spatial resolution. Inactive Cs(I), Ni(II), Nd(III) and natural U(VI) were selected for the experiments chemically representing key radionuclides. The thin sections were prepared on high-purity silicon wafers from geochemically characterized cores of Boda Claystone Formation, Hungary. Samples were subjected to 72-hour sorption experiments with one ion of interest added. The µ-XRF elemental maps taken usually on several thousand pixels indicate a correlation of Cs and Ni with Fe-and K-rich regions suggesting that these elements are predominantly taken up by clay-rich phases. U and Nd was found to be bound not only to the clayey matrix, but the cavity filling minerals also played important role in the uptake. Multivariate methods were found to be efficient tools for extracting information from the elemental distribution maps even when the clayey matrix and fracture infilling regions were examined in the same measured area. By using positive matrix factorization as a new approach the factors with higher sorption capacity could be identified and with additional mineralogical information the uptake capacity of the different mineral phases could be quantified. The results were compared with cluster analysis when the regions dominated by different mineral phases are segmented. The multivariate approach based on µ-XRF to identify the minerals was validated using microscopic X-ray diffraction. Keywords: micro-XRF; sorption; positive matrix factorization; radioactive waste; argillaceous rock IntroductionIn most European countries, clay-rich rocks are considered as suitable host rock formations for isolation of the radionuclides generated by the nuclear industry from the biosphere for thousands of years. During this time period the radionuclides might migrate from the engineered barriers and the safety is determined by the retention capability of the host rock. Following water intrusion into the repository, radionuclide contaminants can be released. Clay rocks have very good retention capability due to their high sorption capacity. Sorption depends on the water/solid compositions, porewater properties such as pH and Eh, as well as the presence of complexing anions as they determine t...

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Actinide Colloids and Particles of Environmental Concern

Cited by 145 publications

References 237 publications

Solvothermal Synthesis of Tetravalent Uranium with Isophthalate or Pyromellitate Ligands

Solvothermal Synthesis of Tetravalent Uranium with Isophthalate or Pyromellitate Ligands

Trace-level plutonium(IV) polymer stability and its transport in coarse-grained granites

Microscale analysis of metal uptake by argillaceous rocks using positive matrix factorization of microscopic X-ray fluorescence elemental maps

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