Sorption of U(VI) onto Opalinus Clay: Effects of pH and humic acid

Joseph, Claudia; Stockmann, Madlen; Schmeide, Katja; Sachs, Susanne; Brendler, Vinzenz; Bernhard, Gert

doi:10.1016/j.apgeochem.2013.06.016

Cited by 42 publications

(43 citation statements)

References 76 publications

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“…The clay gel has a similar composition as the surrounding clay but is slightly enriched in Fe, Ca, and Si. This can be expected since in clay dissolution experiments higher silicon than aluminum concentrations are usually measured (Joseph et al, 2013a). Aluminum probably precipitates as hydroxide on the clay surface (Schroth and Sposito, 1997).…”

Section: U(vi) Diffusion In Mx-80 As a Function Of Densitymentioning

confidence: 87%

“…neutral Ca2UO2(CO3)3(aq) complex and is known to sorb only weakly to minerals (Fox et al, 2006) and clay-rich rock (Joseph et al, 2011). In addition, UO2(CO3)3 4-, the second dominant species in solution, is regarded as a non-sorbing species (Joseph et al, 2013a;Křepelová et al, 2006) since it will be repulsed by the negatively charged clay surface. The low Kd values suggest that U(VI) reduction to U(IV) was negligible in these experiments, although the redox state of uranium sorbed to MX-80 was not experimentally verified.…”

Section: U(vi) Diffusion In Mx-80 As a Function Of Densitymentioning

confidence: 99%

“…They worked at a slightly lower pH and ionic strength compared to the present study, which leads to a different U(VI) speciation and sorption behavior. Under their conditions, (UO2)2CO3(OH)3is most likely the dominant U(VI) species in solution, which is known to sorb stronger to clay than Ca2UO2(CO3)3(aq) (Joseph et al, 2013a;Křepelová et al, 2006), thus yielding higher Kd values. In the case of Glaus and Van Loon (2012), besides the Ca2UO2(CO3)3(aq) complex, a relatively large fraction of various negatively charged uranyl carbonato complexes are present in solution, which, as mentioned before, sorb even less than the Ca2UO2(CO3)3(aq) complex.…”

Section: U(vi) Diffusion In Mx-80 As a Function Of Densitymentioning

confidence: 99%

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Long-term diffusion of U(VI) in bentonite: Dependence on density

Joseph

Mibus

Trepte

et al. 2017

Science of The Total Environment

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As a contribution to the safety assessment of nuclear waste repositories, U(VI) diffusion through the potential buffer material MX-80 bentonite was investigated at three clay dry densities over six years. Synthetic MX-80 model pore water was used as background electrolyte. Speciation calculations showed that CaUO(CO)(aq) was the main U(VI) species. The in- and out-diffusion of U(VI) was investigated separately. U(VI) diffused about 3mm, 1.5mm, and 1mm into the clay plug at ρ=1.3, 1.6, and 1.9g/cm, respectively. No through-diffusion of the U(VI) tracer was observed. However, leaching of natural uranium contained in the clay occurred and uranium was detected in all receiving reservoirs. As expected, the effective and apparent diffusion coefficients, D and D, decreased with increasing dry density. The D values for the out-diffusion of natural U(VI) were in good agreement with previously determined values. Surprisingly, D values for the in-diffusion of U(VI) were about two orders of magnitude lower than values obtained in short-term in-diffusion experiments reported in the literature. Some potential reasons for this behavior that were evaluated are changes of the U(VI) speciation within the clay (precipitation, reduction) or changes of the clay porosity and pore connectivity with time. By applying Archie's law and the extended Archie's law, it was estimated that a significantly smaller effective porosity must be present for the long-term in-diffusion of U(VI). The results suggest that long-term studies of key transport phenomena may reveal additional processes that can directly impact long-term repository safety assessments.

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Section: U(vi) Diffusion In Mx-80 As a Function Of Densitymentioning

confidence: 87%

Section: U(vi) Diffusion In Mx-80 As a Function Of Densitymentioning

confidence: 99%

Section: U(vi) Diffusion In Mx-80 As a Function Of Densitymentioning

confidence: 99%

See 1 more Smart Citation

Long-term diffusion of U(VI) in bentonite: Dependence on density

Joseph

Mibus

Trepte

et al. 2017

Science of The Total Environment

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“…Our work from FY 2013 showed that SGGW/MES solutions at pH 6.9 and 7.9 remained stable for at least 6 months. Uranium adsorption partition coefficients (K d values) onto many different minerals have been reported to vary over several orders of magnitude between pH 7 and 9 (Waite et al, 1994;Echevarria et al, 2001;Davis and Curtis, 2003;Joseph et al, 2013), with essentially zero K d at pH of 9 or higher. For a given pCO 2 , uranium exhibits much stronger adsorption at the low end of this pH range because of the greater abundance of positively-charged uranyl species (U (VI) 2+ and U(OH) + ) and the lesser abundance of nonsorbing neutral and negatively-charged uranyl carbonate or uranyl-Ca/Mg-carbonate complexes at neutral pH.…”

Section: Groundwatermentioning

confidence: 99%

Used Fuel Disposal in Crystalline Rocks: Status and FY14 Progress.

Wang¹

2014

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Executive SummaryThe U.S. Department of Energy Office of Nuclear Energy, Office of Fuel Cycle Technology established the Used Fuel Disposition Campaign (UFDC) in fiscal year 2010 (FY10) to conduct the research and development (R&D) activities related to storage, transportation and disposal of used nuclear fuel and high level nuclear waste. The Mission of the UFDC isTo identify alternatives and conduct scientific research and technology development to enable storage, transportation and disposal of used nuclear fuel and wastes generated by existing and future nuclear fuel cycles.The work package of Crystalline Disposal R&D directly supports the following UFDC objectives: Develop a fundamental understanding of disposal system performance in a range of environments for potential wastes that could arise from future nuclear fuel cycle alternatives through theory, simulation, testing, and experimentation.  Develop a computational modeling capability for the performance of storage and disposal options for a range of fuel cycle alternatives, evolving from generic models to more robust models of performance assessment.The objective of the Crystalline Disposal R&D Work Package is to advance our understanding of long-term disposal of used fuel in crystalline rocks and to develop necessary experimental and computational capabilities to evaluate various disposal concepts in such media.Significant progress has been made in FY14 in both experimental and modeling arenas in evaluation of used fuel disposal in crystalline rocks. The work covers a wide range of research topics identified in the R&D plan. The major accomplishments are summarized below:  A R&D plan was developed for used fuel disposal in crystalline rocks. A total of 31 research topics (9 for system level and 22 for processes level) have been identified. The technical approach to addressing each of these topics is formulated.  A generic reference case for crystalline disposal media has been established. The reference case specifies the emplacement concept, waste inventory, waste form, waste package, backfill/buffer properties, EBS failure scenarios, host rock properties, and biosphere. This is an important step in developing a baseline for total system model development. Three emplacement concepts were specified: waste packages containing 4 PWR assemblies emplaced in boreholes in the floors of horizontal tunnels (for comparison with the KBS-3 concept), a 12-assembly waste package emplaced in tunnels, and a 32-assembly dual purpose canister emplaced in tunnels.  We have developed and applied THMC models to the analysis of coupled EBS processes in bentonite-backfilled repositories. We based this development on the extension of the Used Fuel Disposal in Crystalline Rocks vi 9/26/2014Used Fuel Disposal in Crystalline Rocks 9/26/2014 vii column method for evaluating and parameterizing colloid-facilitated radionuclide transport, using bentonite colloids, Am, and Grimsel Test Site granodiorite FFM as a model system. The method is designed to better interrogate the slowe...

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“…Mineral-U(VI) contaminant interactions have been the subject of many studies [see for example (Qafoku and Icenhower, 2008) and references therein]. It is well-established in the literature that contaminant U(VI) may interact via adsorption and/or reduction reactions with 1) organic matter (Bruggeman et al, 2012;Joseph et al, 2011;Joseph et al, 2013a;Joseph et al, 2013b;Schmeide et al, 2000;Schmeide et al, 2003;Steudtner et al, 2011); 2) Fe oxides (Bargar et al, 1999;Dodge et al, 2002;Duff and Amrhein, 1996;Ho and Miller, 1986;Hsi and Langmuir, 1985;Jang et al, 2007;Lefevre et al, 2006;Moyes et al, 2000;Reich et al, 1998;Rovira et al, 2007;van Geen et al, 1994;Villalobos and Leckie, 2001;Waite et al, 1994;Wazne et al, 2003); 3) phyllosilicates (Catalano and Brown, 2005); 4) micas (Ilton et al, 2006); 5) titanium oxide (Lefevre et al, 2008); 6) calcite (Kelly et al, 2003); 7) quartz (Ilton et al, 2012); 8) chlorite (Singer et al, 2009); 9) biogenic mackinawite (Veeramani et al, 2013); and 10) framboid pyrite (Qafoku et al, 2009). Uranium adsorption has also been studied in sediments from the Hanford site [see, for example, (Dong et al, 2005;Zachara et al, 2005)], and other DOE contaminated sites, such as the one in Rifle, CO (Campbell et al, 2012;Qafoku et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Uranium fate in Hanford sediment altered by simulated acid waste solutions

Gartman

Qafoku

Szecsody

et al. 2015

Applied Geochemistry

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Infiltration of aqueous acidic waste to the subsurface may induce conditions that alter contaminant transport. Experiments were conducted to examine the effects of low pore water pH and associated changes to sediment properties on U(VI) behavior in sediments. Macroscopic batch experiments were combined with a variety of bulk characterization studies (Mössbauer and laser spectroscopy), micron-scale inspections (µ-XRF), and molecular scale interrogations (XANES) with the objectives to: 1) determine the extent of U(VI) partitioning to Hanford sediments exposed to acidic waste simulants and held at pH = 2, pH = 5, or under neutral conditions (pH = 8) at varying ionic strength, and in the presence of air [bench-top (BT) experiments] or in the absence of air [glove-box (GB) experiments]; and 2) determine the uranium micron-scale solid phase and associated valence state resulting from the experimental conditions. The investigation showed minimal overall changes in Fe mineralogy as a result of sediment exposure to acid solutions, but an increase in the highly reactive nano Fe fraction of the sediment. Greater uranium partitioning was observed at pH = 5 than at pH = 2 and 8. The µ-XRF inspections and XANES analyses confirmed that high concentration areas on sediment surfaces were rich in U(VI) in the BT experiments, and both U(IV) and U(VI) in the GB experiments. The laser spectroscopy data showed that uranyl phosphates {e.g., metaautunite [Ca(UO 2 ) 2 (PO 4 ) 2 ·10-12H 2 O] and phosphuranylite [KCa(H 3 O) 3 (UO 2 ) 7 (PO 4 ) 4 O 4 ·8H 2 O]} may have formed in the BT experiments. In the GB experiments, in addition to U(IV) phases, U(VI) phases may have also formed similar to those that are naturally present in the sediment, but at higher concentrations. The results provide insights about U(VI) mobility beneath acidic waste disposal sites.

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Sorption of U(VI) onto Opalinus Clay: Effects of pH and humic acid

Cited by 42 publications

References 76 publications

Long-term diffusion of U(VI) in bentonite: Dependence on density

Long-term diffusion of U(VI) in bentonite: Dependence on density

Used Fuel Disposal in Crystalline Rocks: Status and FY14 Progress.

Uranium fate in Hanford sediment altered by simulated acid waste solutions

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