Comparative photodecolorization of red dye by anatase, rutile (TiO2), and wurtzite (ZnO) using response surface methodology

Treatment of dye pollution containing C.I. Acid Red 14 (AR14) by a coupled photocatalytic process was studied. Titanium dioxide, in the form of anatase and rutile, and zinc oxide, were used as photocatalysts. The investigated photocatalysts were Aldrich-produced nanopowders with crystallites of a mean size 20-30 nm and a specific surface area of about 50 m(2)/g. A comparison of TiO2(anatase), TiO2(rutile), TiO2(a,r), and ZnO for the decolorization of the AR14 solution was performed. Results showed that color removal followed the decreasing order of TiO2(a,r), ZnO > TiO2(a,r) > TiO2(a), ZnO > TiO2(r), ZnO >TiO2(a,r) > TiO2(a) > ZnO > TiO2(r). Response surface methodology (RSM) was employed to assess the individual and interactive effects of the 4 main independent parameters in the photocatalytic process. Analysis of variance showed a high coefficient of determination (R-2 = 0.9396) and satisfactory prediction second-order regression. The optimum initial amounts of TiO2(a), TiO2(r), ZnO. and dye and the reaction time were found to be 84 ppm, 23 ppm, 86 ppm, 20 ppm, and 48 min, respectively. It was demonstrated that RSM with suitable 2D and 3D graphs was a suitable method for finding the interactions between parameters, identifying the main parameters, and optimizing the operating conditions.