Water Sites at a Clay Interface

NMR and computational molecular modeling studies of mineral surfaces and interlayer galleries: A review

“…Development of NMR theory, instrumentation, and applications proceeded rapidly through the 1950s, and the first commercial NMR spectrometers became available in the early 1960s. Application to clay minerals dates at least to the late 1960s, with the early work focusing on adsorbed and interlayer water (e.g., Hecht et al 1966;Touilaux et al 1968;Woessner and Snowden 1969;Hougardy et al 1977;Grandjean 1997;Fripiat et al 1984; and many others). With the advent of the pulse-Fourier transform method of spectral acquisition, high-field superconducting magnets, and the routine use of magic angle sample spinning (MAS) in the late 1970s and early 1980s, it became possible to obtain spectra for a wider variety of nuclei with much higher resolution and signal/ noise ratios than with previous instrumentation.…”

Water Structure and Dynamics in Smectites: X-ray Diffraction and 2H NMR Spectroscopy of Mg–, Ca–, Sr–, Na–, Cs–, and Pb–Hectorite

“…1,3,11,13,16,17,29−33 On the basis of experimental NMR studies, early reports proposed an isotropic rotational diffusion model to explain the room-temperature motions of proximityrestricted H 2 O in smectite−H 2 O pastes and suspensions, 2,10 but more recent NMR, neutron, and MD studies have suggested that anisotropic water motion often dominates over a wide range of water contents and temperatures. 4−8,14 1 H and 2 H NMR results [1][2][3][4][5][6][7][8][9]21,29,34 provide insight into the reorientation mechanisms of proximitiy-restricted H 2 O molecules in 2-dimensional nanoconfinement. Previously published 2 H NMR data for the smectite mineral hectorite exchanged with Na + , K + , and Ca 2+ show that interlayer water undergoes anisotropic rotational reorientation and site exchange dynamics at frequencies in the kilohertz to hundreds of kilohertz range over temperatures from 193 to 298 K and that these dynamics vary significantly with temperature, hydration state of the clay, and the dominant exchangeable cation.…”

Dielectric Dispersion in the Frequency Range 1 MHz–1 GHz of Concentrated Suspensions in Relation to Rheology

“…R40 clay is composed of kaolinite with one site group, ≡ ≡SOH, identified as A1-OH at particle edges (16), where phosphate anions from Tpp are most probably bounded. Na cations are physically adsorbed in association with water molecules on ≡ ≡XH surface sites, which can be assimilated to the edge of silica layers, (17) and on basal surfaces (18). This surface characteristic favors a specific s(τ ) distribution with three distinct peaks (Fig.…”