Comparative study on the process behavior and reaction kinetics in sonocatalytic degradation of organic dyes by powder and nanotubes TiO2

Sonocatalytic degradation of various organic dyes (Congo Red, Reactive Blue 4, Methyl Orange, Rhodamine B and Methylene Blue) catalyzed by powder and nanotubes TiO₂ was studied. Both catalysts were characterized using transmission electron microscope (TEM), surface analyzer, Raman spectroscope and thermal gravimetric analyzer (TGA). Sonocatalytic activity of powder and nanotubes TiO₂ was elucidated based on the degradation of various organic dyes. The former catalyst was favorable for treatment of anionic dyes, while the latter was more beneficial for cationic dyes. Sonocatalytic activity of TiO₂ nanotubes could be up to four times as compared to TiO₂ powder under an ultrasonic power of 100 W and a frequency of 42 kHz. This was associated with the higher surface area and the electrostatic attraction between dye molecules and TiO₂ nanotubes. Fourier transform-infrared spectrometer (FT-IR) was used to identify changes that occurred on the functional group in Rhodamine B molecules and TiO₂ nanotubes after the reaction. Sonocatalytic degradation of Rhodamine B by TiO₂ nanotubes apparently followed the Langmuir-Hinshelwood adsorption kinetic model with surface reaction rate of 1.75 mg/L min. TiO₂ nanotubes were proven for their high potential to be applied in sonocatalytic degradation of organic dyes.