Kinetics of photocatalytic degradation of methylene blue on nanostructured TiO2 coatings created by sol-gel process

Sol-gel process was chosen to produce a photocatalytic film to degrade methylene blue. In order to study structural and morphological properties of the coatings, a base sol of TTIP, I-PrOH, and DEA was prepared. Then with addition of 45g/L PEG 2000, 30g/L TiO2 and 15g/L PEG 2000 + 30g/L TiO2, to the base sol, three other sols were produced. The results of this study indicated that substrate can affect photocatalytic behavior of the coatings. Then different parameters (Sol types, number of dip coating cycles, initial concentration, two wavelengths of 265 and 254 nm and pH) of the study were modified and an equation was derived for each parameter. At last, using all the derived equations, a more general equation was calculated to predict the rate of corrosion based on pH, initial concentration of methylene blue, and number of dip coating cycles. A reactor was designed and tested to investigate the effect of continuous degradation. It was realized that the rate of all photocatalytic reactions were inhibited as a result of higher evaporation and decreased exposure time to coating and ultraviolet light.

Keywords:

TiO2 , Kinetics , Methylene blue , photocatalyst , sol-gel process