title: Hydration sequence of swelling clays: evolutions of specific surface area and hydration energy.
abstract: In order to identify the key steps and the driving force for the hydration process of swelling clays, the water adsorption isotherms and enthalpies were measured on monoionic montmorillonite samples saturated with alkali or calcium ions, and on bi-ionic samples saturated with a sodium-calcium mixture. The specific surface area evolution along the hydration process was determined using a recent interpretation of the experimental adsorption isotherms of swelling solids. Results are interpreted in structural terms. Compared with additional data from sample-controlled thermal analysis (SCTA), the results confirm experimentally that the hydration of Li- and Na-montmorillonite is mainly a cation-controlled process, in contrast with the hydration of Cs samples in which the cation contribution to hydration is negligible, as we have already demonstrated using electrostatic calculations or conductivity measurements.
authors.affiliation: CEA, DEN, SMTM/Laboratoire de Modélisation des Transferts dans l'Environnement, Cadarache, F-13108 Saint-Paul-lez-Durance, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Salles
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Douillard
authors.forename: Renaud
authors.initials: R
authors.lastname: Denoyel
authors.forename: Olivier
authors.initials: O
authors.lastname: Bildstein
authors.forename: Michel
authors.initials: M
authors.lastname: Jullien
authors.forename: Isabelle
authors.initials: I
authors.lastname: Beurroies
authors.forename: Henri
authors.initials: H
authors.lastname: Van Damme
mesh_terms: D000327:Adsorption; D000468:Alkalies / Q000737:chemistry*; D000538:Aluminum Silicates / Q000737:chemistry*; D001546:Bentonite / Q000737:chemistry; D002118:Calcium / Q000737:chemistry*; D002151:Calorimetry; D000077215:Clay; D012964:Sodium / Q000737:chemistry; D013499:Surface Properties; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D000468:Alkalies; D000538:Aluminum Silicates; D014867:Water; D001546:Bentonite; D012964:Sodium; D002118:Calcium; D000077215:Clay