Detection of intermediates in the TiO2-assisted photodegradation of Rhodamine B under visible light irradiation.

The photocatalytic degradation of dye Rhodamine B (RhB) in the presence of TiO2 nanostripe or P25 under visible light irradiation was investigated. The degradation intermediates were identified using Infrared spectra (IR spectra), 1H nuclear magnetic resonance (1HNMR) spectra, and gas chromatography-mass spectroscopy (GC-MS). The IR and the 1HNMR results showed that the large conjugated chromophore structure of RhB was efficiently destroyed under visible light irradiation in both the photocatalytic systems (TiO2 nanostripe or P25 and Rhodamine B systems). GC-MS results showed that the main identified intermediates were ethanediotic acid, 1,2-benzenedicarboxylic acid, 4-hydroxy benzoic acid and benzoic acid, which were almost the same in the TiO2 nanostripes and P25 systems. This work provides a good insight into the reaction pathway(s) for the TiO2-assisted photocatalytic degradation of dye pollutants under visible light irradiation.