Abstract
BACKGROUND: The aim of this study was to investigate improvement of the photocatalytic activity of visible‐light driven nitrogen‐modified TiO~2~ (N‐TiO~2~) powder toward methyl blue (MB) and direct blue‐86 (DB‐86) dyes. The Taguchi method with an L~9~ orthogonal array was applied to plan the synthesis parameters, i.e. nitrogen sources, nitrogen source concentrations, stirring time and calcined temperatures. 95% confirmation experiments were undertaken to verify the effectiveness of the Taguchi method.
RESULTS: All N‐TiO~2~ photocatalysts were shifted toward the visible light region with the optical band gap (Eg). Nitrogen source concentrations were significant parameters for the photocatalytic decolorization rate constants (k values). In comparison with pure TiO~2~, the photodecolorization behavior of N‐TiO~2~ toward DB‐86 was superior with a reaction rate constant of 1.68 × 10^−3^ min^−1^, and a 4 h photodecolorization efficiency of 34%.
CONCLUSION: The Taguchi method was reported to alter the surface properties of commercial Degussa P25 TiO~2~, which could then be used as a visible‐light driven photocatalyst. The visible‐light‐driven photocatalyst was investigated to determine material characteristics. Greater photodecolorization of MB and DB‐86 dye pollutants using optimally‐prepared N‐TiO~2~ under visible light irradiation was successfully obtained. Copyright © 2011 Society of Chemical Industry