The influence of natural organic matter on radionuclide mobility under conditions relevant to cementitious disposal of radioactive wastes: A review of direct evidence

Stockdale, Anthony; Bryan, Nicholas

doi:10.1016/j.earscirev.2013.02.007

Cited by 45 publications

(24 citation statements)

References 106 publications

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“…Natural organic matter (NOM) is recognized as one of the largest input of organic 22 compounds into the repository. Depending on the host rock and location, the concentration of 1 NOM can vary between 0.02 ~ 10 mg/L in granitic waters and 0.9 ~ 127 mg/L in salt dome 2 ground waters ( Stockdale and Bryan, 2013). In the case of Beishan HLW repository in China, the 3 host rock is granite with a low NOM content.…”

Section: Effect Of Organic Matter 21mentioning

confidence: 99%

Re(VII) diffusion in bentonite: Effect of organic compounds, pH and temperature

Wang

et al. 2016

Applied Clay Science

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In order to understand the diffusion properties of anionic radionuclides (RN) in 10 bentonite in the presence of organic compounds with chelating and reducing properties, the effect 11 of humic acid (HA), citrate, oxalate and formate on Re(VII) diffusion were investigated by a 12 through-diffusion method under different pH (pH 7.0 and 10.0) and temperature conditions (10 ~ 13 65 C). When the molar ratio of oxalate to Re(VII) was higher than 1:1, the accumulated mass and 14 flux were observed to decrease drastically as a function of time. It can be explained by 15 photocatalytic impact of Fe(III) on the reduction of Re(VII) to insoluble Re(IV) by oxalate. Thus, 16 the diffusion of Re(VII) was also observed to decrease in the presence of minor citrate, oxalate 17 and formate. Effective diffusion coefficient (D e) values decreased from 8.7  10-11 m 2 /s to (5.1 ~ 18 5.9)  10-11 m 2 /s. In contrast, HA had no significant impact on Re(VII) diffusion. The D e values of 19 1.54  10-11 and 6.5  10-12 m 2 /s were obtained at pH 7.0 and 10.0, respectively. HA thus neither 20

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Section: Effect Of Organic Matter 21mentioning

confidence: 99%

Re(VII) diffusion in bentonite: Effect of organic compounds, pH and temperature

Wang

et al. 2016

Applied Clay Science

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“…Thus, the occurrence and potential interactions of natural chelating agents, i.e. (P)HCA, with radionuclides is of crucial importance for safety assessment of cementitious geological disposal facilities [ 6 , 11 , 12 ].…”

Section: Introductionmentioning

confidence: 99%

Adsorption of aliphatic polyhydroxy carboxylic acids on gibbsite: pH dependency and importance of adsorbate structure

Schneckenburger¹,

Riefstahl²,

Fischer

2018

Environ Sci Eur

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BackgroundAliphatic (poly)hydroxy carboxylic acids [(P)HCA] occur in natural, e.g. soils, and in technical (waste disposal sites, nuclear waste repositories) compartments . Their distribution, mobility and chemical reactivity, e.g. complex formation with metal ions and radionuclides, depend, among others, on their adsorption onto mineral surfaces. Aluminium hydroxides, e.g. gibbsite [α-Al(OH)3], are common constituents of related solid materials and mimic the molecular surface properties of clay minerals. Thus, the study was pursued to characterize the adsorption of glycolic, threonic, tartaric, gluconic, and glucaric acids onto gibbsite over a wide pH and (P)HCA concentration range. To consider specific conditions occurring in radioactive wastes, adsorption applying an artificial cement pore water (pH 13.3) as solution phase was investigated additionally.ResultsThe sorption of gluconic acid at pH 4, 7, 9, and 12 was best described by the “two-site” Langmuir isotherm, combining “high affinity” sorption sites (adsorption affinity constants > 1 L mmol−1, adsorption capacities < 6.5 mmol kg−1) with “low affinity” sites ( < 0.1 L mmol−1, adsorption capacities ≥ 19 mmol kg−1). The total adsorption capacities at pH 9 and 12 were roughly tenfold of that at pH 4 and 7. The S-shaped pH sorption edge of gluconic acid was modelled applying a constant capacitance model, considering electrostatic interactions, hydrogen bonding, surface complex formation, and formation of solved polynuclear complexes between Al3+ ions and gluconic acid. A Pearson and Spearman rank correlation between (P)HCA molecular properties and adsorption parameters revealed the high importance of the size and the charge of the adsorbates.ConclusionsThe adsorption behaviour of (P)HCAs is best described by a combination of adsorption properties of carboxylic acids at acidic pH and of polyols at alkaline pH. Depending on the molecular properties of the adsorbates and on pH, electrostatic interactions, hydrogen bonding, and ternary surface complexation contribute in varying degrees to the adsorption process. Linear distribution coefficients Kd between 8.7 and 60.5 L kg−1 (1 mmol L−1 initial PHCA concentration) indicate a considerable mineral surface affinity at very high pH, thus lowering the PHCA fraction available for the complexation of metal ions including radionuclides in solution and their subsequent mobilization.

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“…With re‐estimation of the half‐life of 79 Se from 65 000 years to much higher values (295 000 , 320 000 or 370 000 years ), 79 Se is presently considered as the key mobile fission product . Special attention has been recently paid to understand the influence of natural organic matter on radionuclide migration . Among others, acetic acid is the simplest organic substance that can act as a building block for humic acids and simulate their structure and functionality .…”

Section: Defining Chemical Equilibriamentioning

confidence: 99%

Affinity capillary electrophoresis in studying the complex formation equilibria of radionuclides in aqueous solutions

Sladkov

2016

Electrophoresis

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Interaction of radionuclides with inorganic and organic species present in natural environment plays an important role in their eventual dispersion. The complex equilibria established in the aqueous phase cause significant changes in the migration properties of radionuclides. Affinity capillary electrophoresis (ACE) can be fruitful in studying these equilibria. This paper reviews the recent methodological advances of the use of ACE in studying the complex equilibria of radionuclides in aqueous solutions. Special attention is paid to the determination of a number of species involved in equilibrium, species constituents (number of ligands, protonated, deprotonated), the influence of ionic strength and temperature on stability constants of complex species formed. Use of ACE for the determination of the main thermodynamic parameters (the molar Gibbs energy (Δ G ), the molar enthalpy (Δ H ) and the molar entropy (Δ S )) of complex formation reactions is also discussed. These data are essential to predict dispersion of radionuclides in the natural environment.

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The influence of natural organic matter on radionuclide mobility under conditions relevant to cementitious disposal of radioactive wastes: A review of direct evidence

Cited by 45 publications

References 106 publications

Re(VII) diffusion in bentonite: Effect of organic compounds, pH and temperature

Re(VII) diffusion in bentonite: Effect of organic compounds, pH and temperature

Adsorption of aliphatic polyhydroxy carboxylic acids on gibbsite: pH dependency and importance of adsorbate structure

Affinity capillary electrophoresis in studying the complex formation equilibria of radionuclides in aqueous solutions

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