Properties of water adsorbed in anionic clays: A neutron scattering study

The properties of the water contained in anionic clays have been investigated as a function of precalcination temperature and gallery height using quasi elastic neutron scattering (QENS). Two representative samples which differ in the geometry of the anions and the latter's hydration chemistry were used. The QENS results reveal that the water molecules are not fixed in one location but exhibit translational diffusion as well as reorientational motions. The diffusion coefficients of the water for both systems are significantly lower than 2.3 x 10(-5) m(2) s(-1), the value for water in bulk. This indicates that the clay water is spatially restricted, a conclusion that is consistent with observations from other spectroscopic methods. In addition to the role played by the gallery height, the sample's pretreatment temperature is observed to affect the mobility of the water.