Hydration of Na, Ni, and Sm in the interlayer of hectorite: a quasielastic neutron scattering study

Quasielastic neutron scattering experiments were performed with Na-hectorite, Ni-hectorite, and Sm-hectorite samples in order to find out whether Sm is present in the clay interlayer as a fully hydrated cation (outer-sphere complex), or, as it follows from neutron diffraction data analysis, it is dehydrated and bound to the clay surface (inner-sphere complex). The results obtained for the Sm-hectorite were compared with other interlayer cations: strongly hydrated Ni and relatively weakly hydrated Na+. It was found that water mobility in the Sm-hectorite sample is very close to the water mobility in Ni-hectorite. This is only possible if the Sm ion is fully hydrated. It was shown that water molecules hydrating Ni and Sm exhibit diffusion in su -0 04 13 84 7, v er si on 1 9 Se p 20 09 Author manuscript, published in "The Journal of Physical Chemistry C 113 (2009) 13801-13812" DOI : 10.1021/jp903179g