Development of organic-Inorganic nanostructured Environmental Photocatalysts with Tunable Molecular Selectivity.

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In this study, combination between molecular selective adsorption and photocatalysis was investigated. n-Octyl-grafted TiO_2 (C8-TiO_2) was prepared as a model of a photocatalyst with high molecular adsorption selectivity, and its photocatalytic activity for the decomposition of dilute 4-nonylphenol (an endocrine disrupter, ca. 2 ppm) in water was investigated. The catalyst was highly active in the presence of concentrated phenol (1000 ppm), and the 4-nonylphenol was decomposed in 180 min, while pristine TiO_2 (P-25) under the same conditions showed much lower activity. The high C8-TiO_2 activity was ascribed to the molecular selective adsorption of the organic molecules on the alkyl-grafted hydrophobic surface. Infrared spectra showed that the grafted alkyl groups were gradually decomposed under photoirradiation. The model catalyst demonstrated that molecular selective adsorption is important for removal of low-concentration contaminants in the presence of other, more concentrated com … More pounds.n-Octyl groups were grafted onto the pore walls of TiO2-MCM-41 in which TiO2 was highly dispersed in the nanopores (8.7wt%as TiO2), and the photocatalytic properties for decomposition of dilute 4-nonylphenol polyethoxylate (NPEO) in water were investigated. The activities were evaluated on the basis of the benzene ring decomposition rates.n-Octyl-grafted TiO2-MCM-41 (C8-TiO2-MCM-41) efficiently decomposed dilute NPEO. The activity of C8-TiO2-MCM-41 per TiO2 weight was higher than that of P-25 TiO2 catalyst under the same conditions. In contrast, the activity of TiO2-MCM-41 without alkyl grafting was low. NPEO at low concentrations in solution (less than 5ppm) was preferentially adsorbed onto C8-TiO2-MCM-41, while the adsorption onto TiO2-MCM-41 under the same conditions was small. The higher activity of C8-TiO2-MCM-41 was ascribed to the highly concentrated NPEO in the hydrophobic nanospaces.Photoirradiation of C8-TiO2-MCM-41 in water for 3h decreased its carbon content by 17%, but further irradiation for 7h brought about only a further 8% decrease, demonstrating a relatively long lifetime for the alkyl groups grafted onto the C8-TiO2-MCM-41. Less