Surface charge density and diffuse layer properties of highly defined 2:1 layered silicate platelets

Titelangaben

Kuznetsov, Volodymyr ; Ottermann, Katharina ; Helfricht, Nicolas ; Kunz, Daniel ; Loch, Patrick ; Kalo, Hussein ; Breu, Josef ; Papastavrou, Georg:
Surface charge density and diffuse layer properties of highly defined 2:1 layered silicate platelets.
In: Colloid and Polymer Science. Bd. 298 (2020) . - S. 907-920.
ISSN 1435-1536
DOI der Verlagsversion: https://doi.org/10.1007/s00396-020-04673-w

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Abstract

Clays are not only ubiquitous in nature, but they are also used in huge quantities in a broad range of industrial applications, such as thixotropic drilling fluids, ore pelletizers, waste disposal sealants, or fillers in polymer nanocomposites. In order to model environmental processes or to design new materials on a rational base, it is of prime importance to determine and possibly modify the interfacial properties of clay platelets at the solid/electrolyte interface. In this context, the fundamental question rises how far the stoichiometric interlayer charges as determined by the composition of the silicate layer correlates with the diffuse double-layer properties. Here, this question is addressed by means of a series of purposely synthesized sodium 2:1 layered silicates with defined composition and hence interlayer charge densities, respectively. Platelets of layered silicates of large enough diameter to perform AFM colloidal probe measurements were produced by melt synthesis. For comparison also, a natural muscovite mica has been included in this study. The diffuse layer properties in electrolyte solution have been determined by direct force measurements using the colloidal probe AFM technique and by electrokinetic measurements, respectively. We find that the diffuse layer potential decreases with increasing interlayer charge of the 2:1 layered silicates. This counterintuitive finding is attributed to ion adsorption and was further corroborated by determining the quantitative adsorption of polyelectrolytes, namely poly(amidoamine) dendrimers.