1H and 7Li NMR pulsed gradient spin echo measurements and multiscale modeling of the water and ionic mobility within aqueous dispersions of charged anisotropic nanoparticles

The mobility of the water molecules and the neutralizing lithium counterions are simultaneously determined in dense dispersions of charged anisotropic nanoplatelets by exploiting H-1 and Li-7 pulsed gradient spin echo NMR measurements, respectively. The strong difference between the measured solvent and ionic mobility results from the specific lithium/clay electrostatic coupling responsible for the ionic condensation of the lithium counterions on the basal surface of these charged nanoplatelets. Such a property should be exploited to enhance the retention capacity of clay sediments used as diffusion barriers for the storing of ionic waste. A multiscale modeling of the ionic condensation and diffusion processes is used to semiquantitatively interpret these measurements by relating the dynamical property of the diffusing probes (water molecule and lithium counterion) and the organization of the clay dispersion.