Modeling uranium(VI) adsorption onto montmorillonite under varying carbonate concentrations: A surface complexation model accounting for the spillover effect on surface potential

Tournassat, Christophe; Tinnacher, Ruth M.; Grangeon, Sylvain; Davis, Jim

doi:10.1016/j.gca.2017.09.049

Cited by 111 publications

(77 citation statements)

References 68 publications

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“…Despite the care to exclude CO 2 from the experiment conducted in the glove-box, alkalinity/DIC concentration values were similar to values obtained in experiments conducted outside the glove-box (Figure 4, bottom). This observation echoes the results of Tournassat et al (2018) on U(VI) adsorption experiments on montmorillonite, where the DIC concentrations measured in "CO 2 -free" experiment ranged from 8.2 10 -3 to 6.2 10 -2 mmol⋅L -1 in the pH range 3.9-9.9.…”

Section: Alkalinity and Dic Concentrationssupporting

confidence: 87%

“…The inadequacy of the classical DLM model to reproduce divalent metal adsorption on montmorillonite surface in a wide range of pH and ionic strength conditions has been put forward repeatedly for more than twenty years Bradbury 1997, Akafia et al 2011). Only recently, a SCM that included the spillover effect in the evaluation of the surface potential was successfully applied to quantify U(VI) adsorption on montmorillonite in a wide range of pH, ionic strength and DIC concentration conditions (Tournassat et al 2018). In this study, quantifying Pb adsorption were investigated on montmorillonite samples, but also on illite samples and on a natural assemblage of illite, illite/smectite mixed layer mineral (IS) and smectite.…”

Section: Choice Of Modelmentioning

confidence: 99%

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From experimental variability to the sorption related retention parameters necessary for performance assessment models for nuclear waste disposal systems: The example of Pb adsorption on clay minerals

Oruçoğlu

Tournassat

Robinet

et al. 2018

Applied Clay Science

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Surface complexation models (SCMs) have been developed in the last decades to describe metal ion sorption to clay minerals and especially to montmorillonite. In principle, these models can provide relevant information about sorption of radionuclides to be used in performance assessment (PA) of radioactive waste disposal systems. However, these SCMs have been developed in parallel with the acquisition of distinct adsorption datasets, which are not always consistent with each other. The objective of this study was to compare new experimental adsorption results with literature data to understand these discrepancies and to propose a SCM approach that could be amenable to determine sorption related retention parameters necessary for PA calculations. This study focused on lead (Pb) adsorption on montmorillonite, illite and in a natural clay (Callovo Oxfordian) as case studies of a strongly sorbing radionuclide that undergoes a range of retention processes depending on the chemical conditions. The experiments showed that many experimental artifacts lead to misinterpretations of the processes underlying the measured retention values. These include Pb precipitation in the presence of carbonate in solution. The determination of SCM parameters to provide sorption related information for PA of clay minerals should rely on preliminary building of an adequate adsorption database, where adequate means that all experimental conditions are met to quantify surface complexation only. *Revised manuscript with no changes marked Click here to view linked References

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Section: Alkalinity and Dic Concentrationssupporting

confidence: 87%

Section: Choice Of Modelmentioning

confidence: 99%

From experimental variability to the sorption related retention parameters necessary for performance assessment models for nuclear waste disposal systems: The example of Pb adsorption on clay minerals

Oruçoğlu

Tournassat

Robinet

et al. 2018

Applied Clay Science

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“…Reaction constants are taken from Spycher et al 2011, most of which are largely consistent with those used in Davis et al (2004). Our speciation calculation is consistent with other studies (Dong et al, 2006;Fox et al, 2006;Stewart et al, 2010, Tournassat et al, 2018 that the dominant ones are Ca 2 UO 2 (CO 3 ) 3 and CaUO 2 (CO 3 ) 3 -2 . A chemical model that neglects these two species could significantly underestimate the total aqueous concentration of U (VI).…”

Section: 84supporting

confidence: 87%

On the long-term migration of uranyl in bentonite barrier for high-level radioactive waste repositories: The effect of different host rocks

Cao¹,

Zheng²,

Hou³

et al. 2019

Chemical Geology

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Repositories for high level radioactive waste hosted in argillite or granite with bentonite backfill are the two disposal concepts that been extensively studied. A general perception is that granite has very low sorption capacity and therefore is disadvantageous in retarding the migration of radionuclides in comparison with argillite. However, when there is bentonite backfill, does the sorption capacity of granite really matter for the migration of radionuclides? How different host rocks would affect the migration of U(VI) through the bentonite backfill of an engineered barrier system (EBS), and which properties of the host rocks cause those differences in migration, given that migration of radionuclides is a critical measure in assessing the performance of a repository? Here we present two coupled thermal, hydrological, and chemical models for the transport of U(VI), each with an identical setup except for the type of host rock (argillite vs granite rock). Comparisons between our models show that the different host rocks exert their influence on migration of U(VI) via regulating the chemical conditions in the bentonite, which affect the concentration of U(VI) at the source and the adsorption of U(VI) in the bentonite. The key chemical conditions are pH, Ca + , and HCO 3-concentration in pore-water, which are strongly affected by soluble carbonate minerals. Our models also show the occurrence of illitization (dissolution of smectite and precipitation of illite) in the bentonite, which affects the migration of U(VI) through changing pH and the quantity of adsorbents. Although generalization of current model results for granite and argillite should be done carefully, the simulations highlight the importance of pore-water chemistry in host rock, as well as bentonite-host rock interactions, when assessing the performance of a repository. In comparison to properties such as thermal conductivity, permeability, and adsorption capacity, properties that have been studied intensively, the pore-water chemistry of host rocks deserve equal or even more attention because of its strong influence on radionuclide migration.

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“…Removal of uranium (VI) from aqueous media presents significant difficulties, since uranyl ions are prone to hydrolysis and formation of various compounds, including anionic, which are hardly removed from aqueous solutions [3]. Cobalt, namely its isotope 60 Со, is also one of the dangerous toxicants, the source of which can be radioactive waste of various origins [4].…”

Section: Literature Review and Problem Statementmentioning

confidence: 99%

“…Cobalt, namely its isotope 60 Со, is also one of the dangerous toxicants, the source of which can be radioactive waste of various origins [4]. Sorption materials based on natural raw materials, including clay minerals, are effective in removal processes [3,5].…”

Section: Literature Review and Problem Statementmentioning

confidence: 99%

Investigation of the structure and sorption peculiarities of cobalt and uranium ions by nanocomposites based on montmorillonite and tetraethoxysilane

Doroshenko

Pylypenko

Kovalchuk³

et al. 2018

EEJET

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6 organisms. One of the most dangerous heavy metals and radionuclides are uranium and cobalt compounds. Uranium compounds are widely used in the nuclear fuel cycle. They get into the environment mainly with the wastewater of hydrometallurgical plants processing uranium ores and also are components of liquid radioactive waste of nuclear power plants [1]. Pollution by cobalt compounds is possible due 6

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Modeling uranium(VI) adsorption onto montmorillonite under varying carbonate concentrations: A surface complexation model accounting for the spillover effect on surface potential

Cited by 111 publications

References 68 publications

From experimental variability to the sorption related retention parameters necessary for performance assessment models for nuclear waste disposal systems: The example of Pb adsorption on clay minerals

From experimental variability to the sorption related retention parameters necessary for performance assessment models for nuclear waste disposal systems: The example of Pb adsorption on clay minerals

On the long-term migration of uranyl in bentonite barrier for high-level radioactive waste repositories: The effect of different host rocks

Investigation of the structure and sorption peculiarities of cobalt and uranium ions by nanocomposites based on montmorillonite and tetraethoxysilane

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