Visible light N-TiO2-induced photodegradation of Congo red: characterization, kinetics and mechanistic study

In this study, the photocatalytic degradation of Congo red has been investigated in N-doped TiO2 (N-TiO2) aqueous suspensions under visible light irradiation. Visible light-active N-TiO2 was successfully prepared at three different weight contents (2.5, 5, and 7%) employing sol-gel method. It was able to harvest the visible irradiation with wavelength suitable for activation. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometer, diffused reflectance UV-Vis spectroscopy, nitrogen adsorption Brunauer-Emmert-Teller, Raman spectroscopy, photoluminescence and X-ray photoelectron spectrometer were used to characterize the doped catalyst. The samples had a relatively large specific Brunauer-Emmert-Teller surface areas of about 42 m(2) g(-1) with average X-ray diffraction crystalline size of 52 nm and showed visible light photocatalytic activity at about 408 nm. The impacts of several operating parameters on the Congo red photodegradation process were examined. Langmuir-Hinshelwood model exhibited pseudo-first-order degradation kinetics. N-TiO2-assisted plausible photodegradation mechanism has been suggested based on the qualitatively detected intermediate compounds.