AN INFRARED SPECTROSCOPIC STUDY OF CARBONATE ADSORPTION TO ZIRCONIUM DIOXIDE SOL-GEL FILMS FROM AQUEOUS-SOLUTIONS

Internal reflection infrared spectroscopy has been used to investigate the formation and nature of surface carbonates on ZrO2 sol-gel films. Films prepared in atmospheres of CO2 and air exhibited an enhancement of bands in the 1600-1300 cm(-1) spectral region compared to films pr epared in an Ar atmosphere. This is due to formation of surface carbon ates from the reaction of atmospheric CO2 with the metal oxide film. B oth bidentate carbonate and bidentate bicarbonate surface species are formed. For in situ solution adsorption studies, ZrO2 sol-gel films we re pretreated with an alkaline wash to remove surface contaminants. Ad sorption from dilute aqueous (HCO3-)-C-12 solutions resulted in the ap pearance of strong infrared absorptions at 1551 and 1349 cm(-1) as wel l as other absorptions at 1091, 1052, 849, and 761 cm(-1). The strong absorptions shifted to 1505 and 1304 cm(-1) with adsorption from dilut e (HCO3-)-C-13 Solutions. The adsorbed species has been assigned to a bidentate carbonate from existing infrared absorption data for both zi rconium carbonato complexes and previously assigned surface carbonate species. Adsorption isotherms were determined from in situ infrared sp ectral measurements of adsorbate absorbances as a function of bicarbon ate solution concentration. A Langmuir isotherm analysis was used to o btain an equilibrium constant for adsorption of 2 x 10(5) M-1, indicat ing a strongly bound surface complex.