Kinetics study for photodegradation of methylene blue dye by titanium dioxide powder prepared by selective leaching method

The kinetics of photodegradation of methylene blue (MB) dye by titanium dioxide (TiO2) powder were investigated using elementary reactions. TiO2 powders were prepared by a selective leaching method consisted of processes of CaHPO4 precipitation, heat treatment, and acid leaching to obtain high crystalline anatase. The obtained TiO2 samples had wide ranges of specific surface areas (5–23 m2/g) and densities of Ti3+ defects (90–480×1012spin/g) without a significant change in the anatase phase ratio ranging 0.86–0.91 in mass ratio. The MB photodegradation rate was expressed as functions of specific surface area and density of Ti3+ defects under the experimental condition that the photodegradation rate was proportional to UV irradiation intensity and the adsorbed MB amount was proportional to specific surface area. A proposed equation for calculation of photodegradation ate demonstrated greater effect of specific surface area than density of Ti3+ defects for MB photodegradation.

► Kinetics of photodegradation of dye were studied by assuming reaction model. ► Transformation to rutile phase was suppressed by precipitated CaHPO4. ► Photocatalytic activity was expressed as functions of surface area and Ti3+ density. ► Specific surface area had stronger effect than Ti3+ density.