Degradation of methylene blue and acetaminophen with Fe-TiO₂ nanoparticles catalyzed by UV/visible light and sunlight

Fe-doped TiO₂ nanoparticles (nFe-TiO₂) with various Fe concentrations (0.0, 0.1, 0.2 and 1 wt%) were prepared using a sol–gel method. The photocatalytic activity of nFe-TiO₂ was evaluated through the degradation of acetaminophen (ACE) under UV and visible light. nFe-TiO₂ induces a significant red shift to extend the absorption wavelength range from UV to visible light, identified by spectra analysis of UV/vis diffuse reflectance spectroscopy. The results show that higher Fe doping amount lead to lower reaction rate constants and degradation efficiency for methylene blue and ACE with nFe-TiO₂ under UV light. However, under xenon lamp irradiation, which includes the visible light region, an increase in the reaction rate constant of nFe-TiO₂ is observed. In general, the ACE degradation efficiency of the catalysts tested is better under sunlight than under the xenon lamp, possibly due to the higher light intensity of sunlight. Tests at various pH levels show that pH 7.0 yields the best ACE degradation with nTiO₂. After three reuse tests, the nFe-TiO₂ still had a good ACE degradation efficiency (> 95%). The optimal operation parameters obtained are 20 mg nFe-TiO₂ with a calcination temperature of 500 °C for TiO₂ and Fe contents of 0.2%, which shows the best ACE removal of 99.9% under sunlight within 4.5 h and 55.1% under visible light (580 nm) within 8 h. Therefore, nFe-TiO₂ can enhance the photocatalytic activity of TiO₂ for ACE removal under sunlight and visible light (580 nm).