The structural environments of cations adsorbed onto clays: 133Cs variable-temperature MAS NMR spectroscopic study of hectorite

Reversibility of radiocaesium sorption on illite

“…It has been observed Coleman et al, 1963) that caesium sorption increases the affinity of the vermiculite clay for caesium due to collapse of the vermiculite lattice and reduction of the interlayer spacing to ϳ10 Å , the dehydrated interlayer spacing. This mechanism of caesium sorption on vermiculite is corroborated by 133 Cs MAS NMR data, which show that at high concentrations sorbed on vermiculite, caesium is present in dehydrated form (Weiss et al, 1990a;Weiss et al, 1990b).…”

Vibrational Probe Studies of Water Interactions with Montmorillonite

“…This hypothesis is consistent with our data, in that the environment around partially solvated metal cations should be less ordered than under hydrated conditions. Additional evidence is provided by recent NMR spectroscopic studies of exchangeable cations on montmorillonite (Weiss et al, 1990a(Weiss et al, , 1990bLaperche et al, 1990) where the line-broadening observed at low water contents is attributed to a decreased mobility of the cation, and by interactions between the cation and the clay mineral surface itself.…”

“…When less than three molecular layers of water are present in the interlamellar region, the structure of sorbed water on smectites has been shown to be influenced predominantly by exchangeable cations (Mooney et al, 1952b;Clementz et al, 1973Clementz et al, , 1974Prost, 1975;McBride, 1982;Sposito and Prost, 1982;Sposito et al, 1983;Bidadi et al, 1988;Grandjean and Laszlo, 1989;Kogelbauer et al, 1989;Hall and Astill, 1989;Trillo et aL, 1990;Fu et aL, 1990;Delville et aL, 1991;Tinet et al, 1992). Spectroscopic investigations of smectite-water interactions (Prost, 1975;Sposito and Prost, 1982;Brown and Kevan, 1988;Weiss et al, 1990a;Bank et al, 1991;Tinet et al, 1992) suggest that two distinct environments of sorbed water are present: 1) water molecules coordinated directly to exchangeable metal cations, and 2) physisorbed water molecules occupying interstitial pores, interlameUar spaces between exchangeable metal cations, or polar sites on external surfaces.…”

Molecular dynamics simulations of the electrical double layer on smectite surfaces contacting concentrated mixed electrolyte (NaCl–CaCl2) solutions

“…Models of the EDL that approximate liquid water as a uniform dielectric continuum (such as the Poisson-Boltzmann equation [17,18], hypernetted chain theory [19,20], or the primitive model [18,21]) inherently cannot describe surface complexes [17,18]. Spectroscopic methods that probe the local molecular environment of "reporter atoms" (for example, nuclear magnetic resonance (NMR) [22,23] or x-ray absorption spectroscopy (XAS) [24,25]) have shown that adsorbed inorganic ions can adopt several different configurations that include both fully-and partly-solvated species. Resonant anomalous x-ray reflectivity (RAXR) studies, which probe solute concentration as a function of distance from a planar surface, have confirmed that EDL ions can adsorb simultaneously in both ISSCs and OSSCs [26][27][28][29][30].…”