ROLE OF SILANOL GROUPS IN DISPERSING MO(VI) ON SILICA

Infrared spectroscopy was used to follow the intensity of the isolated silanol stretching mode during the reversible transformation of supported molybdenum between the hydrated, polymolybdate structure and the dehydrated, isolated Mo6+ structure. The isolated silanol absorbance intensity was attenuated upon dehydration and spreading of Mo6+. The Si-OH (or Si-OD) silanol band was regenerated by rehydration with H2O (or D2O). A model for spreading is proposed in which the surface silanol groups are the sites for attachment of the isolated Mo6+ cation.