Coupled mechanics, hydraulics and sorption properties of mixtures to evaluate buffer/backfill materials

Jan, Yi-Lin; Tsai, Shiow-Chwen; Wei, Yuan-Yaw; Tung, Ning-Chien; Wei, Chia-Chen; Hsu, Chao-Hsing

doi:10.1016/j.pce.2005.11.002

Cited by 10 publications

(4 citation statements)

References 14 publications

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“…19,20 Compacted bentonite is a particularly suitable and widely considered backfill material as it has high radionuclide sorption capacity, high swelling potential, high plasticity and very low hydraulic conductivity. 21,22 Many studies investigating the influence of humic acids on U(VI) sorption on various other minerals have recently been carried out and reported in the literature, [23][24][25][26][27][28] however, most of the experiments have been performed at a relatively high uranium concentration level, beyond 10 À7 M, while the concentration range in which the actinides may exist in nature is reported to be below 10 À10 M. 29 The main aim of the current work is to study the effect of humic acid on uranyl sorption on bentonite and the distribution of uranium in the U(VI)-humic acid-bentonite ternary system as a function of the order of addition, equilibration time, ionic strength and pH. The effect of the order of addition in the ternary system was examined in order to test the reversibility of the uranium sorption on bentonite in the presence of humics.…”

Section: Introductionmentioning

confidence: 99%

The effect of humic acid on uranyl sorption onto bentonite at trace uranium levels

et al. 2012

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The effect of humic acid (HA) on U(VI) sorption on bentonite was studied in batch experiments at room temperature and ambient atmosphere at a (237)U(VI) concentration of 8.4 × 10(-11) M and HA concentration of 100 mg L(-1). The distribution of U(VI) between the liquid and solid phases was studied as a function of pH and ionic strength both in the absence and presence of HA. It was shown that the uranyl sorption on bentonite is strongly dependent on pH and the presence of humics, and the effect of the addition order was negligible. In the absence of HA an enhancement in the uptake with increasing pH was observed and a sharp sorption edge was found to take place between pH 3.2 and 4.2. The presence of HA slightly increases uranium(VI) sorption at low pH and curtails it at moderate pH, compared to the absence of HA. In the basic pH range for both the presence and absence of HA the sorption of uranium is significantly reduced, which could be attributed to the formation of soluble uranyl carbonate complexes. The influence of ionic strength on U(VI) and HA uptake by bentonite were investigated in the range of 0.01-1.0 M, and while there was an enhancement in the sorption of humic acid with increasing ionic strength, no significant effect of the ionic strength on the U(VI) sorption was observed in both the absence and presence of HA.

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Section: Introductionmentioning

confidence: 99%

The effect of humic acid on uranyl sorption onto bentonite at trace uranium levels

et al. 2012

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“…The anion discussion in this review will be limited to common anions and oxyanions in nuclear waste, including I – , IO 3 – , SeO 3 2– , and TcO 4 – . Relative to cations, anion uptake to any clay mineral is weak and much slower which is consistent with charge repulsion between the fixed negative charge and the anions. ,− For example, selenite required a minimum of 5 days to reach equilibrium with illite and smectite, and iodide required at least 7 days . With traditional metal oxides, anion sorption decreases with increasing pH; this should also be true for the amphoteric edge sites in clays.…”

Section: Internal Structure–functionmentioning

confidence: 81%

Radionuclide Interaction with Clays in Dilute and Heavily Compacted Systems: A Critical Review

Miller

Wang

2012

Environ. Sci. Technol.

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Given the unique properties of clays (i.e., low permeability and high ion sorption/exchange capacity), clays or clay formations have been proposed either as an engineered material or as a geologic medium for nuclear waste isolation and disposal. A credible evaluation of such disposal systems relies on the ability to predict the behavior of these materials under a wide range of thermal-hydrological-mechanical-chemical (THMc) conditions. Current model couplings between THM and chemical processes are simplistic and limited in scope. This review focuses on the uptake of radionuclides onto clay materials as controlled by mineral composition, structure, and texture (e.g., pore size distribution), and emphasizes the connections between sorption chemistry and mechanical compaction. Variable uptake behavior of an array of elements has been observed on various clays as a function of increasing compaction due to changes in pore size and structure, hydration energy, and overlapping electric double layers. The causes for this variability are divided between "internal" (based on the fundamental structure and composition of the clay minerals) and "external" (caused by a force external to the clay). New techniques need to be developed to exploit known variations in clay mineralogy to separate internal from external effects.

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“…In surface disposal projects, the selection of buffer barrier materials is the key to preventing radioactive waste from diffusing into the environment. The types of backfilling and barrier materials determine the effectiveness of the barrier system [9]. In recent years, in the process of using surface disposal methods to treat radioactive wastes, the barrier materials chosen by countries worldwide include clay, cement, and gypsum [10].…”

Section: Introductionmentioning

confidence: 99%

Comparison of Adsorption Capacity and Removal Efficiency of Strontium by Six Typical Adsorption Materials

Li¹,

Han

Shang³

et al. 2022

Sustainability

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The rapid development and application of nuclear technology have been accompanied by the production of large amounts of radioactive wastes, of which Sr is a typical nuclide. In this study, six typical materials with strong adsorption properties, namely activated carbon, kaolin, montmorillonite, bentonite, zeolite, and attapulgite, were selected. Their adsorption mechanisms were investigated by analyzing their adsorption isotherms, adsorption kinetics, micromorphologies, element contents, specific surface areas, crystal structures, and functional groups. The results showed that the adsorption efficiency of Sr by the six adsorbents can be ranked as zeolite, bentonite, attapulgite, montmorillonite, activated carbon, and kaolin, among which the maximum adsorption capacity of zeolite was 4.07 mg/g. Based on the adsorption kinetic and thermodynamic fitting results, the adsorption of Sr by zeolites, bentonite and attapulgite is consistent with Langmuir model, the pseudo-first-order and pseudo-second-order model, and the adsorption process of Sr (II) by montmorillonite, activated carbon and kaolinite is consistent with the Freundlich model and corresponds to non-uniform adsorption. The main mechanisms of the six materials are physical adsorption, ion exchange and complexation. In summary, zeolite, bentonite, and attapulgite, especially zeolite, are highly effective for the treatment of radioactive wastewater containing strontium and have great application value in the treatment of radioactive wastes.

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Coupled mechanics, hydraulics and sorption properties of mixtures to evaluate buffer/backfill materials

Cited by 10 publications

References 14 publications

The effect of humic acid on uranyl sorption onto bentonite at trace uranium levels

The effect of humic acid on uranyl sorption onto bentonite at trace uranium levels

Radionuclide Interaction with Clays in Dilute and Heavily Compacted Systems: A Critical Review

Comparison of Adsorption Capacity and Removal Efficiency of Strontium by Six Typical Adsorption Materials

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