title: Coagulation of Na-montmorillonite by inorganic cations at neutral pH. A combined transmission X-ray microscopy, small angle and wide angle X-ray scattering study.
abstract: The coagulation of sodium montmorillonite by inorganic salts (NaNO3, Ca(NO3)2 and La(NO3)3) was studied by combining classical turbidity measurements with wide-angle-X-ray scattering (WAXS), small-angle-X-ray scattering (SAXS), and transmission X-ray microscopy (TXM). Using size-selected samples, such a combination, associated with an original quantitative treatment of TXM images, provides a true multiscale investigation of the formed structures in a spatial range extending from a few ångstroms to a few micrometers. We then show that, at neutral pH and starting with fully Na-exchanged samples, coagulation proceeds via the formation of stacks of particles with a slight mismatch between layers. These stacks arrange themselves into larger porous anisotropic particles, the porosity of which depends on the valence of the cation used for coagulation experiments. Face-face coagulation is clearly dominant under those conditions, and no evidence for significant face-edge coagulation was found. These structures appear to arrange as larger clusters, the organization of which should control the mechanical properties of the flocs.
authors: Laboratoire Interdisciplinaire des Environnements Continentaux, UMR 7360 CNRS-Université de Lorraine, Vandœuvre, France. laurent.michot@univ-lorraine.fr
authors: Laurent J
authors: LJ
authors: Michot
authors: Isabelle
authors: I
authors: Bihannic
authors: Fabien
authors: F
authors: Thomas
authors: Bruno S
authors: BS
authors: Lartiges
authors: Yves
authors: Y
authors: Waldvogel
authors: Céline
authors: C
authors: Caillet
authors: Juergen
authors: J
authors: Thieme
authors: Sérgio S
authors: SS
authors: Funari
authors: Pierre
authors: P
authors: Levitz
mesh_terms: D001546:Bentonite / Q000737:chemistry*; D002412:Cations / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008853:Microscopy; D012542:Scattering, Radiation; D053838:Scattering, Small Angle; D012964:Sodium; D014961:X-Ray Diffraction
chemical_list: D002412:Cations; D001546:Bentonite; D012964:Sodium