Photocatalytic degradation of Direct Red 16 dye under visible light irradiation using Fe-doped TiO2/Al2O3 nanocatalyst: experimental design and optimization using a central composite design

In this study, Fe-doped TiO (2)/Al2O3 hybrid as a visible active photocatalyst was synthesized by solgel technique. The characteristics of nanocatalyst with optimum composite (5.20 wt.% of Fe3+ and 0.27 wt. ratio of Al2O3) were also investigated by X-ray diffraction, field emission scanning electron microscopy and diffuse reflectance spectra (DRS). The DRS spectra approved that the adsorption wavelength of Fe-doped TiO2 /Al2O3 is in the visible light range (470 nm). The photodegradation of Direct Red 16 dye was carried out to evaluate the photoactivity properties of the prepared samples under visible light irradiation. The influence of weight fraction of Fe3+ (wt.%), Al2O3/TiO2 wt. ratio and contact time on Direct Red 16 photodegradation was modeled and optimized using a central composite design based on response surface methodology. As the analysis of variance results, among significant variables, the Fe3+/Ti4+ weight percentage has a maximum effect on the response. Also, the efficiency of the photocatalytic process for the degradation of dye was enhanced after coupling Al2O3 with Fe-TiO2. Maximum dye removal was achieved by about 99% under the optimum conditions of 5.2 wt.% Fe3+/Ti4+, wt. ratio of 0.27 Al2O3/TiO2 and contact time equally of 112.6 min. Regression analysis with the R-2 value of 0.9736 showed a good agreement between the experimental results and the predicted values.