Thermodynamic properties of anhydrous smectite MX-80, illite IMt-2 and mixed-layer illite–smectite ISCz-1 as determined by calorimetric methods. Part I: Heat capacities, heat contents and entropies

Hélène Gailhanou (1, 2, 3) , J.C. van Miltenburg (4) , J. Rogez (5) , J. Olives (2) , M. Amouric (2) , E.C. Gaucher (1) , Philippe Blanc (1)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
2 CRMCN - Centre de recherche de la matière condensée et des nanosciences
3 ANDRA - Agence Nationale pour la Gestion des Déchets Radioactifs
4 HU - University of Applied Sciences [Utrecht]
5 TECSEN - Laboratoire de thermodynamique, propriétés électriques, contraintes, structures aux échelles nanométriques

The heat capacities of the anhydrous international reference clay minerals, smectite MX-80, illite IMt-2 and mixed-layer illite–smectite ISCz-1, were measured by low temperature adiabatic calorimetry and differential scanning calorimetry, from 6 to 520 K (at 1 bar). The samples were chemically purified and Na-saturated. Dehydrated clay fractions <2 μm were studied. The structural formulae of the corresponding clay minerals, obtained after subtracting the remaining impurities, are ( ) for smectite MX-80, ( for illite IMt-2 and ( )for mixed-layer ISCz-1. From the heat capacity values, we determined the molar entropies, standard entropies of formation and heat contents of these minerals.

Domaines: Sciences de la Terre

Hélène Gailhanou, J.C. van Miltenburg, J. Rogez, J. Olives, M. Amouric, et al.. Thermodynamic properties of anhydrous smectite MX-80, illite IMt-2 and mixed-layer illite–smectite ISCz-1 as determined by calorimetric methods. Part I: Heat capacities, heat contents and entropies. Geochimica et Cosmochimica Acta, 2007, 71 (22), pp.5463-5473. ⟨10.1016/j.gca.2007.09.020⟩. ⟨hal-03640644⟩