Optimization of photo-degradation of direct blue 258 using nano Titanium Oxide with response surface method

The photodegradation of Direct Blue 258, a member of the group of azo dyes which are commonly used in the various branches of the industry, was studied. The photostability of this dye was not previously surveyed. Photocatalytic degradation method was evaluated. The both light source include solar simulated (UV 400 W lamp) and sun light (E= 400 W/m2) and titanium dioxide nanoparticles were used as irradiation sources and photocatalysts, respectively. Several factors such as reaction time, pH and nano-TiO2 concentration and UV source were investigated. Using a 24 factorial matrix, the pH and the nano-TiO2 concentration are the main parameters influencing the degradation rate of DB258. Subsequently, a central composite design methodology has been investigated to determine the optimal experimental parameters for DB258 degradation. After only 30 min of treatment time, high removal of DB258 was achieved by the photo catalyst process under day light (96 %) compared to the UV 400 W lamp. The day light and UV 400 W lamp applied under optimal operating conditions (at 30 min, 0.5 g/L nano-TiO2 and under pH 7) is capable to degrade around 96 % and 96.4 % of DB258, respectively. Since, UV source is not only hazardous but also expensive because of large input of electric power to generate UV irradiation. According to the results, sunlight assisted nano-TiO2 could be effectively used for photocatalytic degradation of pollutants in wastewater.