Hydration of Na+, Ni2+, and SM3+ in the Interlayer of Hectorite: A Quasielastic Neutron Scattering Study

作者：Sobolev Oleg^*; Le Forestier Lydie; Gonzalez Miguel A; Russina Margarita; Kemner Ewout; Cuello Gabriel J; Charlet Laurent

来源：Journal of Physical Chemistry C, 2009, 113(31): 13801-13812.

DOI：10.1021/jp903179g

Quasielastic neutron scattering experiments were performed with Na-hectorite, Ni-hectorite, and Sm-hectorite samples in order to find out whether Sm3+ is present in the clay interlayer as a fully hydrated cation (outersphere 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 Ni2+ 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 Sm3+ ion is fully hydrated. It was shown that water molecules hydrating Ni2+ and Sm3+ exhibit diffusion mobility measurable with backscattering spectrometers. The diffusion coefficients of the exchangeable cations were found using the slow exchange approximations D-Ni = (0.05 - 0.14) x 10(-9) m(2)/s and D-sm = (0.04 - 0.18) X 10(-9) m(2)/s.

• 出版日期2009-8-6