Abstract
The objective of this study was to evaluate, using methylene blue (MB), the effects of various light sources on the bleaching action of hydrogen peroxide (H2O2) with two titanium dioxide (TiO2) photocatalysts — an ultraviolet light-activated TiO2 photocatalyst (UVTiO2) versus a visible light-activated TiO2 photocatalyst (VL-TiO2). Five experimental solutions (VL-TiO2+H2O2, UV-TiO2+H2O2, H2O2, VL-TiO2, UV-TiO2) were prepared by mixing varying concentrations of H2O2 and/or TiO2 photocatalyst with MB solution. For H2O2-containing solutions (VL-TiO2+H2O2, UV-TiO2+H2O2, and H2O2), the concentration of H2O2 was adjusted to 3.5%. For the four different light sources, low- and high-intensity halogen lamps and blue LED LCUs were used. All the experimental solutions were irradiated by each of the light sources for 7 minutes, and the absorbance at 660 nm was measured every 30 seconds to determine the concentration of MB as an indicator of the bleaching effect. On the interaction between the effects of light source and bleaching treatment, the high-intensity halogen with VL-TiO2+H2O2 caused the most significant reduction in MB concentration. On the effect of light sources, the halogen lamps resulted in a greater bleaching effect than the blue LED LCUs.
