Nuclear Magnetic Resonance (NMR) Study of Cd2+ Sorption on Montmorillonite

Paola Di Leo1 and Paul O'Brien2
1 Istituto di Ricerca sulle Argille, CNR, Area di Ricerca di Potenza, Via S. Ioja, 85050 Tito Scalo (PZ), Italy
2 Imperial College of Science, Technology and Medicine, South Kensington, SW72AY London, England
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Abstract: 113Cd solid-state nuclear magnetic resonance (NMR) was used to identify possible Cd2+ adsorption sites in montmorillonite. The montmorillonite was treated with 0.1 and 1 M CdCl2 aqueous solutions and samples with 13 and 8-µm particle size were used. The data are consistent with a two-site model for sorption of Cd2+ on montmorillonite. Cd2+ is localized in the montmorillonite in two different sites: 1) in the interlayers as hydrated Cd2+ and 2) on the external surface, probably with few H2O molecules hydrating to it. Cadmium is also adsorbed as CdCl+ in the interlayer. Treatment with a 0.1 M CdCl2 solution produces adsorption of free Cd2+ in the interlayer whereas treatment with 1 M CdCl2 resulted in adsorption of Cd2+ in both the interlayer and on surface sites and the adsorption of CdCl+ in the interlayer. A larger particle size favors Cd2+ adsorption on the external surface whereas a smaller particle size favors Cd2+ adsorption in the interlayer.

Key Words: Adsorption • Cadmium • Montmorillonite • Nuclear Magnetic Resonance

Clays and Clay Minerals; December 1999 v. 47; no. 6; p. 761-768; DOI: 10.1346/CCMN.1999.0470611
© 1999, The Clay Minerals Society
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