Destruction of <i>o</i>-Chloroaniline in UV/TiO₂ Reaction with Photosensitizing Additives

Abstract

The photodecay of o -chloroaniline ( o -ClA) in TiO 2 suspension with and without the use of additives was examined under an ultraviolet light at 300 nm. An analysis showed that the disappearance of o -ClA followed a pseudo first-order reaction and can be described by the Langmuir−Hinshewood (LH) model. The application of various dosages of TiO 2 indicated a discontinuous linear increment at a break point of 0.1 g L -1 TiO 2 . The change in the system pH has a significant effect on the performance of the process. This is a mixed result of the surface charge of TiO 2 and the chemical characteristic of o -ClA, which is discussed in detail in this paper. The further enhancement of the UV/TiO 2 process by adding H 2 O 2 is feasible if the dosage is carefully controlled. The addition of excess amounts of H 2 O 2 should be avoided to minimize the scavenging of hydroxyl radicals in the solution and valence-band holes at the TiO 2 surface. The use of the sensitizer Rose Bengal (RB) in the UV/TiO 2 process, however, is not suggested. This is because RB is not sensitive at the optimal wavelength for the photocatalytic process involving TiO 2; in addition, the RB may become an additional competitor (with the probe) for the free radicals and active sites on the TiO 2 surface.