study of parameter setting and characterization of visible-light driven nitrogen-modified commercial TiO₂ photocatalysts

An optimal condition applied to the Taguchi method with an L₉ orthogonal array for preparing a visible-light driven nitrogen-modified TiO₂ (N-TiO₂) photocatalyst by a simple hydrolysis method has been examined for material characteristics and a photodecolorization test of methyl blue (MB) under various visible light source (fluorescent and blue LED lamps) irradiations. Results of the material characterization showed that the absorption of prepared N-TiO₂ powder exhibited a significant extension into visible light regimes with an optical bandgap (Eg) of around 2.96eV, which subsequently improved the visible-light photocatalytic activity of N-TiO₂ samples. The superior photocatalytic properties, the pseudo first-order reaction rate constants (k) and photodecolorization efficiency (η%) of a N-TiO₂ photocatalyst during the photodecolorization test of methyl blue (MB) under two different visible light irradiations were very evident compared to those for pure TiO₂. For photodecolorization of practical dyeing from the waste water from the dyeing and finishing industry, a higher photodecolorization efficiency of N-TiO₂ powder toward Direct blue-86 (DB-86) (Direct Fast Turquoise Blue GL) dye was also achieved.