Photocatalytic degradation of direct red 16 dye under visible light irradiation using fe-doped tio2 /al2 o3 nanocatalyst: Experimental design and optimization using a central composite design

Abstract

In this study, Fe-doped TiO2 /Al2 O3 hybrid as a visible active photocatalyst was synthesized by sol– gel technique. The characteristics of nanocatalyst with optimum composite (5.20 wt.% of Fe3+ and 0.27 wt. ratio of Al2 O3 ) 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 /Al2 O3 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 sam-ples under visible light irradiation. The influence of weight fraction of Fe3+ (wt.%), Al2 O3 /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 cou-pling Al2 O3 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 Al2 O3 /TiO2 and contact time equally of 112.6 min. Regression analysis with the R2 value of 0.9736 showed a good agreement between the experimental results and the predicted values.