Adsorptions of Iso- and Terephthalaldehydes on 3-Aminopropyl-Functionalized SBA-15 with Various Loadings

Isophthalaldehyde and terephthalaldehyde (m- and p-benzenedialdehydes, respectively) are adsorbed on 3-aminopropyl-functionalized SBA-15 with loadings of 1.1, 1.4, 1.5, and 1.8 mmol g−1. The data are analyzed by fitting with Langmuir adsorption isotherms. For both isomers, the adsorption capacity gradually increases with increasing loading. In contrast, in the adsorption of the m-isomer, the Langmuir constant considerably increases with loading (by a factor of 8.6), while the increase is limited in the case of p-isomer (by a factor of 1.6). This large difference, which is due to structural isomerism of adsorbate, can be explained by the ease of matching of the two aldehyde functions to 3-aminopropyl groups densely populated on the surface. The adsorption model is supported by the results of IR spectroscopy.