(224c) Photocatalytic Degradation of Organic Contaminants Using Multifunctional Titanosilicate Ets-10

Semiconductor photocatalysis has attracted increasing attention in recent years as an alternative to traditional physical, chemical, or biological technologies for environmental remediation. The photocatalyst market is expected to reach US $10 billion in the near future. Engelhard titanosilicate ETS-10 is a microporous (~4.9 Å x 7.6 Å) zeotype material. The well-defined monatomic -O-Ti-O-Ti-O- chains in ETS-10 with a band gap energy of ~4.03 eV make this semiconductor material a promising candidate for photocatalytic applications. ETS-10 has been reported to exhibit shape selectivity during the photodegradation of phenol, 1,3,5-trihydroxybenzene, and 2,3-dihydroxynaphthalene [1]. The photocatalytic activity of ETS-10 after transition metal ion exchange or isomorphous substitution exhibited comparable or even higher activity than Degussa P25, considered a photocatalytic standard [2]. An investigation was performed to design an effective immobilized ETS-10 photocatalytic film or membrane for degradation of organic contaminants. To successfully achieve this project goal, small ETS-10 crystals with an effective diameter of ~690 nm were hydrothermally synthesized using anatase as the Ti source and N-Brand sodium silicate as the Si source. These crystals were then used to prepare ETS-10 films on optical fiber substrates that will be used as the means of light transmission and distribution into ETS-10 photocatalyst. Sol-gel process with a single dip-coating step resulted in nearly complete surface coverage of the optical fibers and an apparent a(b)-out-of-plane preferred orientation of the ETS-10 crystals. The thin film integrity was further improved utilizing a secondary (seeded) growth step for short times (i.e., £4 h). This resulted in high seed crystal intergrowth. In order to evaluate the photocatalytic activity of these ETS-10 thin films, an optical fiber reactor system was designed and optimized. The obtained photocatalytic efficiency will be quantified and compared with that reported for standard TiO₂ photocatalyst Degussa P25.

[1]Calza P, Pazé C, Pelizzetti E, Zecchina A. Shape-selective photocatalytic transformation of phenols in an aqueous medium. Chem. Commun. 2001;2130-2131.

[2] Uma S, Rodrigues S, Martyanov IN, Klabunde KJ. Exploration of photocatalytic activities of titanosilicate ETS-10 and transition metal incorporated ETS-10. Micropor. Mesopor. Mater. 2004;67:181-187.