Sorption and Leaching Properties of the Composites and Complexes of Natural Microporous Materials

Macášek, F.

doi:10.1007/978-94-011-4499-5_8

Cited by 4 publications

(2 citation statements)

References 60 publications

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“…In this way, the conditioning process aims to immobilize the mobile contaminants by solidification, embedding or encapsulation methods in order to minimize their potential dispersion and migration (Palmer and Fairhall 1992;Krishnamoorthy et al 1993). Cementation (Coumes and Courtois 2003), bituminization (Kluger et al 1980) and vitrification (Lee et al 2006) are common techniques for the immobilization of low-and intermediate-level radioactive wastes, the former being the most used worldwide (Barinov et al 1990;Coumes and Courtois 2003;Rahman et al 2014), in which the immobilization occurs by precipitation and adsorption of the mobile contaminants (Macášek 1999;Real et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Effect of Chloride and Sulfate in the Immobilization of Cs-137 in C-S-H Gel

Duque-Redondo

Yamada

Manzano

2021

ACT

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Cementitious materials are commonly used in nuclear repository sites to immobilize intermediate-level radioactive wastes. This is due to the large surface area of the calcium silicate hydrate (C-S-H) gel, the main hydration product of ordinary Portland cement, which provides many sorption sites in which the contaminants can be adsorbed. The retention capacity of these materials is strongly dependent on the composition, the water content, the pH or the presence of additives. Likewise, it is also known that the durability and performance of cement and concrete are adversely affected in chloride and/or sulfate environments. In this work, atomistic simulations have been employed to analyze the effect of the presence of chlorides and sulfates in the retention and transport of 137 Cs, one of the most hazardous radioisotopes, in calcium silicate hydrate. The simulations suggest that the presence of a moderate amount of chlorides does not alter significantly the Cs uptake in C-S-H gel, while a moderate content of sulfates enhances substantially the retention of Cs ions and reduces their migration throughout the pore. This behavior is attributed to the ability of the sulfates to pull Ca out the high-affinity sites from the C-S-H surface, allowing Cs ions to occupy them.

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Section: Introductionmentioning

confidence: 99%

Effect of Chloride and Sulfate in the Immobilization of Cs-137 in C-S-H Gel

Duque-Redondo

Yamada

Manzano

2021

ACT

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“…Cementation has been used worldwide by the nuclear industry for immobilization of radioactive, hazardous and mixed wasted, since cementitious materials act as a diffusion barrier thanks to their large surface area which provides multiple sorption and reaction sites [8][9][10][11] . Moreover, these materials have many other advantages, such as the low cost processing, high thermal, chemical and physical stability of the resulting wasteform, high durability, they are non-flammable and not degraded by radiation or the possibility of being processed remotely 12,13 .…”

Section: Introductionmentioning

confidence: 99%

Adsorption and Diffusion of Na+, Cs+ and Ca+2 Ions in C-S-H and C-a-S-H Nanopores

Duque-Redondo¹,

Yamada²,

Arbeloa³

et al. 2018

Preprint

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Cementitious materials act as a diffusion barrier, immobilizing liquid and solid radioactive waste and preventing their release into the biosphere. The retention capability of hydrated cement paste and its main hydration product, C-S-H gel, has been extensively explored experimentally for many alkali and alkaline earth cations. Nevertheless, the retention mechanisms of these cations at the molecular scale are still unclear. In this paper, we have employed molecular dynamics simulations to study the capacity of C-S-H to retain Cs, Ca and Na, analyzing the number of high-affinity sites on the surface, the type of sorption for each cation and the diffusivity of these ions. We have also explored the impact of aluminum incorporation in C-S-H at a constant concentration of the ions in the gel pore. We found strong competition for surface sorption sites, with notable differences in the retention of the cations under study and a remarkable enhance of the adsorption in C-A-S-H with respect to C-S-H.

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