In-situ infrared spectroscopic studies of adsorption processes on boehmite particle films: exchange of surface hydroxyl groups observed upon chelation by acetylacetone.

Adsorption processes on poorly crystalline boehmite (PCB) particle films have been studied using attenuated total reflection infrared spectroscopy. This method allows the in-situ investigation of wet surface chemical processes. Thin films of aggregated particles of PCB that are stable between pH 4 and 11 have been prepared by drying aqueous PCB dispersions. Carbonate adsorbs to the PCB films during the film formation process but can be removed without impact on the film by washing with alkali at pH 10. The adsorption of acetylacetone (acac) to the surface of PCB has been studied at the solid/liquid and solid/gas interfaces. The concomitant changes in the OH deformations of hydroxyl groups present on the surface has been observed. The IR absorption of surface hydroxyl groups involved in adsorption of a bidentate chelating ligand have been spectroscopically isolated through their interaction with acac.