Optimization of Methylene Blue Photocatalytic Degradation over TiO2 P25 via Central Composite Design: Kinetic and Statistical Analysis

Abstract

Photocatalytic degradation of methylene blue (MB) dye over TiO2 metal oxide under 
UV radiations was optimized using a central composite design of response surface 
methodology. The effect of TiO2 loading, MB initial concentration, and pH were 
studied in the range the 0.25-2 g/L, 15–35, and 2.5-8.5 ppm, respectively. The cubic 
model was suggested for the response because is more reliable and accurate than the 
quadratic model. The influence of three operational parameters (catalyst loading, 
initial MB concentration, and pH) was examined to maximize the photocatalyst 
performance. The significance of the model and regression coefficients was tested by 
the analysis of variance. Optimal conditions obtained from statistical analysis at 
catalyst loading of 1 gL-1, initial MB concentration of 25 mgL-1 and pH of 2.5 have 
shown MB percentage degradation of 67.47. The kinetics of the photocatalytic 
degradation of MB dye over TiO2 under UV light (3 W) at a wavelength of 253 nm 
was nicely followed by pseudo-first-order kinetic. Moreover, the results predicted by 
the models were found to be in good agreement with those obtained by performing 
experiments (R2 = 0.9993 and Adj-R2= 0.9542).