Water Mobility in Chalk: A Quasielastic Neutron Scattering Study

Abstract

Water mobility through porous rock has a role to play in many systems, such as contaminant remediation, CO 2 storage, and oil recovery. We used inelastic and quasielastic neutron scattering to describe water dynamics in two different chalk samples that have similar pore volume (ranging from tens of micrometers to a few nanometers) but different water uptake properties. We observed distinct water populations, where the analysis of the quasielastic data shows that after the hydration process most of the water behaves as bulk water. However, the lack of quasielastic signal, together with the observation of a translational mode at 10 meV, imply that in chalk samples that take up less water confinement occurs mostly in the pore volume that is accessible with nitrogen adsorption measurements.

CO2 Capture by Nickel Hydroxide Interstratified in the Nanolayered Space of a Synthetic Clay Mineral

“…It is possible that these changes also are associated with local changes of the water population. Following this reasoning, the peak that gains intensity at 64 cm –1 could suggest a more ordered water population . The sharp vibration at 655 cm –1 could also originate from a specific librational mode associated to this ordered water state, possibly through segregation of some water molecules to monomers and dimers .…”

“…The presence of these assigned water populations is further confirmed by analyzing the low energy region of the spectra. Free bulk water 54 is characterized with an excitation around 50 cm −1 , while confined water molecules are characterized by a vibrational mode centered at about 80 cm −1 . 54,55 Thus, the observation of the sharp peak at 76 cm −1 is indicative of interlayer water coordinated to the Ni 2+ cation, while the observation of a broad shoulder toward 50 cm −1 , also observed recently by Larsen et al, 55 is consistent with the presence of water that is not coordinated with cations.…”

“…Following this reasoning, the peak that gains intensity at 64 cm −1 could suggest a more ordered water population. 54 The sharp vibration at 655 cm −1 could also originate from a specific librational mode associated to this ordered water state, possibly through segregation of some water molecules to monomers and dimers. 58 Water confinement in UO 2 F 2 displays a peak at 778 cm −1 , that simulations attribute to a librational phonon mode along the a/b-axis at 712 cm −1 , due to confined water within the van der Waals gap of that material.…”

Nanoscale Mobility of Aqueous Polyacrylic Acid in Dental Restorative Cements

“…Even though bulk water and its dynamics under confinement have been widely studied using neutron spectroscopy, ,,,,,,,− QENS spectra of water at body temperature were measured using the IRIS spectrometer to facilitate the analysis of our data. The QE response was fitted using eq , approximate to one single Lorentzian, and the random jump diffusion model, given in eq , was used to model the extracted hwhm (Γ water ) as a function of Q 2 .…”

Water and Ion Dynamics in Confined Media: A Multi-Scale Study of the Clay/Water Interface

“…For that purpose, numerous dynamical studies have been performed to probe, over a broad dynamical range, the mobility of ions [9,10] and molecules [11][12][13] physisorbed at the clay/water interface. As illustrated in Figure 1, we selected to use a complementary set of experiments, including Inelastic Neutron Scattering (INS) [14][15][16][17][18][19], Quasi-Elastic Neutron Scattering (QENS) [12,[20][21][22][23][24][25][26][27][28][29][30], Nuclear Magnetic Resonance (NMR) relaxometry [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49], Pulsed-Gradient Spin-Echo (PGSE) attenuation [11,[50][51][52], Magnetic Resonance Imaging (MRI)…”