Response surface methodology analysis of the photodegradation of methyl orange dye using synthesized TiO2/Bentonite/ZnO composites

In this research, a modified TiO2/Bentonite (Be) composite with various values of zinc oxide was used as a photocatalyst in the degradation of methyl orange as a dye pollutant. The synthesized composites were characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), and Thermal gravimetric analysis (TGA). The results showed that the composite synthesized by 6.5% zinc oxide had the highest anatase phase and appropriate thermal stability. Moreover, the simultaneous effect of different parameters was investigated using the central composite (CC) design defined under response surface methodology (RSM). The results showed that the polynomial model obtained from the analysis of variance (ANOVA) correctly predicted the experimental data. The optimal conditions of dye degradation for the synthesized composite with 6.5% zinc oxide using 4 g/L of photocatalyst for 30 minutes at a pH=5 and a dye concentration of 20 ppm had the highest degradation percentage equal to 95% with a high desirability of 0.981. Also, the photocatalytic activity of TiO2/Be/ZnO (6.5%) in certain conditions for reuse in five consecutive steps showed a slight decrease in the degradation of methyl orange.