Enhanced sorption and photodegradation of chlorophenol over fluoride-loaded TiO2

The presence of NaF in the aqueous suspension of TiO2 can accelerate the photocatalytic degradation of organic pollutants. However, disposal of such a fluoride-containing wastewater is not allowed by environmental regulation. In the present work, we report on surface modification of TiO2 with a hardly water soluble salt, fluorite and fluorapatite. The modified catalysts at low loading displayed a higher activity than bare TiO2 for the sorption and photocatalytic degradation of phenol and 2,4-dichlorophenol in water. A kinetic study using butanol as hydroxyl radical scavenger revealed that the fluoride-modified catalysts produced more hydroxyl radicals than bare TiO2. Five repeated experiments showed that the fluorapatite-modified TiO2 was very stable, and could be re-used without significant loss in activity. (C) 2011 Elsevier B.V. All rights reserved.