New insights into the molecular structures, compositions, and cation distributions in synthetic and natural montmorillonite clays

Sylvian Cadars*, Régis Guégan, Mounesha N. Garaga, Xavier Bourrat, Lydie Le Forestier, Franck Fayon, Tan Vu Huynh, Teddy Allier, Zalfa Nour, Dominique Massiot

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

64 Citations (Scopus)

Abstract

We present a detailed investigation of the molecular structure of montmorillonite, an aluminosilicate clay with important applications in materials sciences, such as for catalysis, drug delivery, or as a waste barrier. Solid-state 29Si, 27Al, 25Mg, and 1H nuclear magnetic resonance (NMR) measurements combined with density functional theory (DFT) calculations provide a comprehensive picture of the local structure and composition of a synthetic clay and its naturally occurring analogue. A revised composition is proposed based on NMR results that allow the identification and quantification of the signatures of otherwise undetectable noncrystalline impurities, thus largely complementing the traditional elemental analyses. Solid-state 1H NMR at fast magic-angle spinning (MAS) and high magnetic field provide quantitative information on intra- and interlayer local environments that are crucial for the determination of the amount of Mg/Al substitution within the octahedral layer. In combination with DFT calculations of energies, it suggests that pairs of adjacent Mg atoms are unfavorable, leading to a nonrandom cationic distribution within the layers.

Original languageEnglish
Pages (from-to)4376-4389
Number of pages14
JournalChemistry of Materials
Volume24
Issue number22
DOIs
Publication statusPublished - 2012 Nov 27
Externally publishedYes

Keywords

  • 2:1 clays
  • NMR
  • ab initio calculations
  • first-principles calculations
  • layered alumino-silicates
  • smectite

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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