Multinuclear Magnetic Resonance Studies on Aqueous Suspensions of Synthetic Saponites

✍ Scribed by J. Grandjean; J.-L. Robert

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 112 KB
• Volume: 187
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1996.4686

✦ Synopsis

in the octahedral layer (4, 5). This gives rise to two types The structure at the liquid/solid interface of synthetic saponites of counterions as confirmed recently by Monte-Carlo calcuis monitored by NMR methods. These results are compared with lations on hydration of dioctahedral clays (6-8). Near tetradata obtained with a natural saponite. The mean orientation of hedral substitution sites, sodium cations form strong innerinterfacial water molecules is different for synthetic and natural sphere surface complexes. More loosely outer-sphere surface saponites. Interaction of water molecules or counterions with the complexes are associated with the substitution in the octahesolid surface depends on the charge layer of the synthetic clays. dral layer (7, 8). In this latter case, water clusters near the Water/acetonitrile and sodium/tetrapropylammonium cation clay surface have been postulated from thermodynamic and competitions have been studied. Significant changes of the orientacontact angle measurements (9). The stronger interaction tion of interfacial water molecules and removal of sodium counterions are observed only with the lowest charged saponite. ᭧ 1997 associated with tetrahedral substitution destroys these aggre-Academic Press gates, and interfacial water molecules are mainly associated Key Words: clay interface; water orientation; synthetic saponite; with the counterions. When both octahedral and tetrahedral NMR visibility; quadrupolar nuclei.

substitutions are present, NMR studies have also displayed two interfacial water sites (10)(11)(12). Raman studies in the OH-stretching region have allowed differentiation of two