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2019
ACL
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H.Gailhanou, P.Blanc, J.Rogez, G.Mikaelian, H.Kawaji, J.Olives, V.Montouillout, J.M.Grenèche, P.Vieillard, E.C.Gaucher, C.I.Fialips, B.Made, 'Thermodynamic properties of mixed-layers illite-smectite by calorimetric methods. Acquisition of the enthalpies of mixing of illite and smectite layers', The Journal of Chemical Thermodynamics 138 78-97 (2019) doi:10.1016/j.jct.2019.06.004
The stability of illite-smectite interstratified with respect to discrete illite and smectite minerals was
investigated by measuring their thermodynamic properties. The standard thermodynamic properties of
the illite-smectite ISCz-1 mineral (G, H, S, Cp, and V) were determined between 298.15 K and 375 K by
using calorimetric methods. Moreover, the enthalpies of mixing between the illite and smectite layers
were measured at 298.15 K by acid solution calorimetry from a complete series of illite-smectite interstratified
minerals (Shinzan area, Japan). The measured values were slightly negative, with a minimum
value of 3.7 kJ.mol1. This contributed to the stability of the mixed-layer with respect to a mechanical
mixture of illite and smectite. In addition, the model from Blanc et al. (2015) was implemented to estimate
the thermodynamic properties of the interstratified illite-smectite ISCz-1 mineral. The predicted
values were consistent with the experimental results. However, the estimates were slightly improved
by considering the thermodynamic properties of the mixture of the illite and smectite components
and then adding the terms of energies of mixing. This could be confirmed by establishing the stability
domains of ISCz-1 and those of the corresponding illite and smectite end-members according to
Meunier and Velde’s determination of the smectite to illite reaction pathways (Meunier and Velde, 1989).
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