Towards a link between the energetic heterogeneities of the edge faces of smectites and their stability in a context of metallic corrosion

Murielle Perronnet (1, 2) , Frédéric Villiéras (1) , Michel Jullien (2) , Angelina Razafitianamaharavo (1) , Joël Raynal (2) , Dominique Bonnin (3)

1 LEM - Laboratoire Environnement et Minéralurgie
2 LMTE - Laboratoire de Modélisation des Transferts dans l'Environnement
3 LPQ - Laboratoire de Physique Quantique

In the context of the potential confinement of high-level radioactive wastes (HLW) within clay Engineered Barrier System (EBS) in deep geological formation, the evolution of the retention properties of smectite when interacting with Fe(0) needs to be assessed. If some potential natural analogues describing the iron-clay reactivity are easily found, metallic iron-clay interactions are poorly described on Earth. Therefore experimental investigations are needed. Several parameters influence Fe(0)-clay interactions such as temperature, interlayer composition of swelling clays, presence of octahedral Fe3+... On a geometrical point of view it is thought that clay destabilization is mainly controlled by phenomena starting at the edge faces of the particles. In the present work, the rates of the smectite-Fe(0) reaction at 80°C were assessed by XRD, Mössbauer and CEC analyses for three smectites. These ones show marked differences in stability degree which, however, can not be explained by the crystal-chemistry rules established in previous studies. Therefore, the Fe(0)-smectites interactions were studied in view of textural and energetic surface quantitative analyses. The studied smectites have equivalent nitrogen BET specific surface areas, equivalent argon edge surface areas and slightly different basal surface areas. This similarity in particle shape indicates that the edge surface area can not be accounted for to explain the observed differences in reactivity. But, a correlation is obtained between smectite reactivity and the energetic heterogeneity of its edge faces. This is interpreted in terms of a multiplication of the number of sites on the edge faces where the electron transfer between Fe(0) and the smectite structure can occur.

Mots clés: smectites; Iron; alkaline dissolution; Surface area; low-pressure argon adsorption; edge faces; energetic heterogeneity

Domaines: Minéralogie; Géologie appliquée; Interfaces continentales, environnement; Chimie théorique et/ou physique

Murielle Perronnet, Frédéric Villiéras, Michel Jullien, Angelina Razafitianamaharavo, Joël Raynal, et al.. Towards a link between the energetic heterogeneities of the edge faces of smectites and their stability in a context of metallic corrosion. Geochimica et Cosmochimica Acta, 2006, -, ⟨10.1016/j.gca.2006.12.011⟩. ⟨hal-00122775⟩