Figure 3.

Contaminant-activated visible light photocatalysis. (a) Hypothetical mechanism of contaminant-activated visible light photocatalysis. (b) and (c) Effect of light wavelength on photocatalytic degradation rate of Mordant Orange (MO) and Procion Red (PR) on anatase coatings. Light control uses silica as an inert coating. Relative contribution of wavelength bands to the overall degradation rate (0.018 hr⁻¹ for MO and 0.023 hr⁻¹ for PR). The wavelength bands evaluated were determined by the lower bound of emission (385 nm) from the fluorescent lamps used for illumination and the cutoff wavelengths (400, 495, 550 nm) of the longpass optical filters employed. The ratio of contaminants MO and PR was 1 µg contaminant per 10 µg of TiO₂ or SiO₂. N = 4.