Photocatalytic transformation of organic compounds in the presence of inorganic anions. 1. Hydroxyl-mediated and direct electron-transfer reactions of phenol on a titanium dioxide-fluoride system
The effect of fluoride ions on the photocatalytic degradation of phenol in an aqueous suspension of TiO{sub 2} has been investigated. Fluoride ions displace surficial hydroxyl groups and coordinate surface-bound titanium atoms directly. For 0.01 M fluoride concentration and 0.10 g/L of TiO{sub 2} in the range pH 2-6, the degradation rate of phenol is up to 3 times that in the absence of fluoride ions. This behavior has been correlated with the computed surface speciation. The decrease in the degradation rate of phenol as a function of the substrate concentration observed in naked TiO{sub 2} at a high concentration of phenol (over 0.01 M) is largely diminished in the presence of fluoride ions. A photocatalytic model which takes into account the primary events and recombination reactions is able to account for these experimental results. The competition events and recombination reactions is able to account for these experimental results. The competition between OH-radical-mediated reaction versus direct electron transfer is discussed. Finally, under a helium atmosphere and in the presence of fluoride ions, phenol is slowly but significantly degraded, although total organic carbon does not decrease, suggesting the occurrence of a photocatalytically induced hydrolysis.
- Research Organization:
- Univ. di Torino (IT)
- OSTI ID:
- 20050875
- Journal Information:
- Langmuir, Vol. 16, Issue 6; Other Information: PBD: 21 Mar 2000; ISSN 0743-7463
- Country of Publication:
- United States
- Language:
- English
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