Enhancement of TiO2 photocatalytic activity under visible light by doping with Cu from electroplating wastewater

In order to improve TiO 2 activity under visible light while exploiting the highly concentrated Cu in electroplating wastewater, doping of Cu from the wastewater into TiO 2 has been addressed. Bare TiO 2 and Cu-doped TiO 2 were synthesized using the sol–gel method with different initial doping amounts of Cu. The prepared photocatalysts were characterized through X-ray diffractometer, Fourier-transform infrared spectrometer, scanning electron microscope, transmission electron microscope, and UV–Vis specular reflectance spectrometer. Photocatalytic activity of the samples under visible light was evaluated through methylene blue degradation. The results show that Cu from wastewater has been successfully doped into TiO 2 , introducing a narrower band gap energy and higher photocatalytic activity under visible light than bare TiO 2 . This study shows that the initial doping amount of Cu influenced the properties and photocatalytic activity of doped TiO 2 . The 6 mg/g Cu-doped TiO 2 sample exhibits the most significant narrowing of band gap energy (2.878 eV) and the highest photocatalytic activity (93.30% of dye degradation). Moreover, the Cu-doped photocatalyst could be reused up to five photodegradation cycles with no significant activity decrease. Graphical abstract