ABSTRACT A general view about formation process, structural characterization, thermal behaviour, interlayer adsorption and reactivity of crystalline silicic acids is depicted from IR, NMR (1H, 23Na and 29Si), XRD and chemical analysis data. The layers of the silicic acids are built up by two types of silica tetrahedra: those sharing their four oxygens with other tetrahedra and those pointing out of the layer and bearing one OH group. The OH groups are responsible for the interlamellar cohesion, the interaction with intercalated molecules, and the reactions with silylating agents giving new organosilicon compounds whose surface properties depend on the attached groups. The study is focused on the layer silicic acids derived from natural and synthetic samples of magadiite. The obtained silicic acids are compared with amorphous silica as well as the silicic acids derived from silicates of thinner (Na2Si2O5, kanemite and KHSi2O5) and thicker (related kenyaite) layers.
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