The effects of surface modification of nanocrystalline titanium dioxide (TiO2) with specific chelating agents on photocatalyic degradation of nitrobenzene (NB) was investigated in order to design a selective and effective catalyst for removal of nitroaromatic compounds from contaminated waste streams. Mechanisms of NB adsorption and photodecomposition were investigated using infrared absorption and electron paramagnetic resonance spectroscopy. Liquid chromatography and gas chromatography/mass spectrometry were used for byproduct analyses. Arginine, lauryl sulfate, and salicylic acid were found to bind to TiO2 via their oxygen-containing functional groups. Modification of the TiO2 surface with arginine resulted in enhanced NB adsorption and photodecomposition, and compared to unmodified TiO2. The initial quantum yield for photodegradation of NB in this system was found to be Φ(init) = 0.31 as compared to the one obtained for Degussa P25 of Φ(init) = 0.18. NB degradation followed a reductive pathway over arginine-modified TiO2 and was enhanced upon addition of methanol. No degradation of arginine was detected under the experimental conditions. Arginine improved the coupling between NB and TiO2 and facilitated the transfer of photogenerated electrons from the TiO2 conduction band to the adsorbed NB. These results indicate that surface modification of nanocrystalline TiO2 with electron-donating chelating agents is an effective route to enhance photodecomposition of nitroaromatic compounds.
ASJC Scopus subject areas
- Environmental Chemistry