Statistical optimization of photocatalytic degradation process of methylene blue dye by SnO-TiO2-AC composite using response surface methodology

Photocatalytic activity of bi-metal oxides SnO-TiO2-AC photocatalyst was evaluated in methylene blue (MB) dye degradation In this study, a three-level, four-factor, D-optimal experimental design, combined with response surface methodology, was employed to optimize the photocatalytic degradation process of MB dye in a batch reactor. Effectiveness of essential process variables: light intensity (254-400 nm), initial dye concentration (100-200 ppm), photocatalyst dose (0.5-1.5 g/L), and irradiation time (1-5 h) were investigated, modeled, and optimized successfully. To determine the process efficiency, the final concentration of dye together with degradation percentage was defined as response variables. Analysis of variance indicated that the proposed quadratic polynomial models agreed with the experimental study with R-2 and p-value of 0.9211, p < 0.001 and 0.8166, p < 0.05 for a final concentration of dye and degradation percentage, respectively. Numerical optimization was carried out based on the desirability function for maximum dye removal. Accordingly, dye removal conditions resulted in light intensity, initial dye concentration, photocatalyst dose, and irradiation time of 400 nm of visible light, 100 ppm, 1.5 g/L, and 3.77 h, respectively. Under these optimal conditions, the final dye concentration and degradation percentage were 4.713 ppm and 95.28%. According to Pareto analysis, the order of the operating variables on the dye degradation efficiency was: photocatalyst does < irradiation time < light intensity < initial concentration of dye.