Hydration of Na , Ni2 , and Sm3 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 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 DNi 0.05 0.14 10 9 m2 s and DSm 0.04 0.18 10 9 m2