Characterization of Polynuclear Ni Species at the Surface of Phyllosilicates, Gibbsite and Amorphous Silica Using Diffuse Reflectance Spectroscopy

Abstract

Formation of a polynuclear Ni phase at the surface of phyllosilicates has been previously observed by EXAFS (Scheidegger et al., 1997). The exact nature of these precipitates is still in discussion (e.g. Charlet and Manceau, 1994), mainly because the second shell cations Si and A1 may not be unequivocally discriminated, and because differences between the Ni-O distances of several possible structures are close to the sensitivity limit of EXAFS (O'Day et al., 1994). Thus, we investigated the potential of diffuse reflectance spectroscopy (DRS) in the UV-vis-NIR range to further elucidate the structure of these precipitates. DRS should be more sensitive to small changes in bond distances than EXAFS (Marco de Lucas et al., 1995).