Impact of the kind of ultraviolet light on the photocatalytic degradation kinetics of the TiO2/UV process

Advanced oxidation processes have gained importance in the last decade because of their application in the treatment of wastewater containing toxic, recalcitrant, and/or colored compounds. The catalyst TiO2, activated with ultraviolet (UV) light, has been used for the degradation of different kinds of compounds, but its activation has been performed with different varieties of UV light without a clear reason for choosing any of the three wavelengths that can be generated with commercially available sources. This work evaluates the degradation speed of acid blue 9 dye through the activation of TiO2 with the different kinds of UV light (UV-A, UV-B, and UV-C). The results indicate that the wavelength of the light used for photoactivation has an impact on the dye degradation speed; shorter wavelengths lead to faster degradation. The analysis of the possible causes affecting the degradation speed was performed by superposing the emission bands of the used UV light with the absorption bands of the dye and catalyst. It is concluded that the interaction zone between the type of UV light and the catalyst notoriously impacts the degradation kinetics. (C) 2011 American Institute of Chemical Engineers Environ Prog, 30: 318-325, 2011