Multiscale Water Dynamics within Dense Clay Sediments Probed by ²H Multiquantum NMR Relaxometry and Two-Time Stimulated Echo NMR Spectroscopy

Abstract

2 H NMR spectroscopy, relaxometry, and two-time correlation measurements are used to investigate the structural and dynamical properties of water molecules confined within the multiscale porous network of dense clay sediment. The residual quadrupolar splitting detected by 2 H NMR spectroscopy is the fingerprint of the specific orientation of the water molecules pertaining to the first hydration shell of clay lamellae. Multiquantum 2 H NMR relaxation measurements are used to quantify the distribution of the clay platelet orientations within the dense sediment. The average residence time of the water molecules confined within the clay interlamellar space is determined by exploiting 2 H multiquantum NMR relaxation measurements under spin-locking conditions. Finally, long-time scale diffusion of the water molecules within the multiscale porous network of the clay sediment is quantified by measuring the attenuation of the 2 H NMR two-time stimulated echo.

Multi-Quanta Spin-Locking Nuclear Magnetic Resonance Relaxation Measurements: An Analysis of the Long-Time Dynamical Properties of Ions and Water Molecules Confined within Dense Clay Sediments

“…In the case of heavy water molecules confined within the clay sediments, we have measured by 2 H NMR the time evolution of two independent coherences [52] (namely T 20 and T 22 (a, s)) in addition to the classical longitudinal and transverse magnetizations corresponding respectively to the T 10 and T 11 (a, s) coherences (see Figure 6a). Let us call R ij the corresponding relaxation rates.…”

“…Let us call R ij the corresponding relaxation rates. The pulse sequence used to measure these different relaxation rates was detailed in previous publications [52]. A first general feature of these relaxation measurements of confined fluid is the large difference between the transverse and longitudinal relaxation rates (i.e., R 11 R 10 ; see Figure 6a).…”

“…Four independent measurements of the relaxation of the T 20 , T 11 , T 22 and T 10 coherences lead then to the four dominant contributions (U Q , J Q 0 (0), U D and J D 0 (0)) quantifying the quadrupolar and heteronuclear dipolar relaxation mechanisms [51,52].…”

“…To test the potentiality of that new approach, we selected the clay/water interface because natural and synthetic clays are well characterized and exploited in numerous industrial applications. In that context, we used multi-quanta NMR relaxometry to quantify the mobility of water molecules (heavy water D 2 O) [40,[50][51][52][53] and neutralizing counterions ( 7 Li [54], 133 Cs [55]) diffusing within the porous network of clay sediments.…”

“…We have used multi-quanta spin-locking NMR relaxometry measurements to determine the average residence time of the water molecules and some neutralizing counterions within the interlamellar space between the clay platelets inside each micro-domain. Furthermore, two-time stimulated echo NMR spectroscopy [59] was used to quantify the time-scale required by the water molecules to probe micro-domains with different orientations [52,53,60].…”