Hydration of Na+, Ni2+, and Sm3+ in the Interlayer of Hectorite: A Quasielastic Neutron Scattering Study

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• 作者：Oleg Sobolev ; Lydie Le Forestier ; Miguel A. Gonzlez ; Margarita Russina ; Ewout Kemner ; Gabriel J. Cuello ; Laurent Charlet
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：August 6, 2009
• 年：2009
• 卷：113
• 期：31
• 页码：13801-13812
• 全文大小：416K
• 年卷期：v.113,no.31(August 6, 2009)
• ISSN：1932-7455

文摘

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 (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 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) × 10⁻⁹ m²/s and D_Sm = (0.04 − 0.18) × 10⁻⁹ m²/s.