Degradation of hydrophobic organic pollutants by titania pillared fluorine mica as a substrate specific photocatalyst

• Published in: Applied catalysis. B, Environmental Environmental, 2005-01, Vol.55 (2), p.141-148
• Main Authors: Shimizu, Ken-ichi, Murayama, Hitoshi, Nagai, Ayumi, Shimada, Aiko, Hatamachi, Tsuyoshi, Kodama, Tatsuya, Kitayama, Yoshie
• Format: Article
• Language: English
• Subjects: Degradation; Persistent organic pollutants; Photocatalysis; TiO2 pillared clays
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2004.08.005

The photocatalytic degradation of a highly hydrophobic and stable organic pollutant, γ-hexachlorocyclohexane (γ-HCH), was performed in aqueous suspended mixture of TiO2-containing catalysts. Unlike most of the organic pollutants, γ-HCH was very stable under the conventional photocatalytic condition with TiO2 (P25). Among various catalysts, TiO2 pillared fluorine mica (Ti-mica) showed highest activity. The effect of preparation method of Ti-mica was also examined. The hydrothermal treatment increased the crystallinity of anatase pillar of Ti-mica, though the treatment at high temperature resulted in a decrease in the surface area and an increase in the pore size. Consequently, Ti-mica treated at lowest temperature (373K), Ti-mica-373, was the most effective photocatalyst. The catalytic activity of TiO2 and Ti-mica-373 was compared for 13 kinds of organic compounds with various hydrophobicity. Ti-mica-373 showed 5–66 times higher rate than TiO2 for the degradation of hydrophobic organic pollutants (α, β, γ and δ-HCH, trans- and cis-chlordane, DDE, DDD and DDT) of low concentration (10ppb). In contrast, TiO2 showed higher rate than Ti-mica-373 for the degradations of less hydrophobic compounds (benzonitrile, chlorobenzene, 4-chloroacetophenone and 4-chloronitrobenzene). Over TiO2-mica-373, organic compounds with higher logPOW value, i.e. more hydrophobic compounds, were decomposed with higher rate. A positive effect of the fluorine mica support is suggested to be caused by the interaction of hydrophobic reactant with the hydrophobic interlayer surface of pillared-clay.