Effects of Calcination on Structural, Photocatalytic Properties of TiO₂ Nanopowders Via TiCl₄ Hydrolysis

Photocatalytic degradation of methyl orange (MO) in water was examined using TiO₂ nanopowders under solar irradiation. These photocatalysts were successfully synthesized by hydrolysis of titanium tetra chloride (TiCl₄) in the temperature range of 70-95 °C and calcined at higher temperatures of between 400 and 900 °C. The samples prepared were characterized using x-ray powder diffraction, scanning electron microscope (SEM) and Fourier transform infrared spectrophotometer (FTIR). UV-Vis spectrometer was used for analyzing the concentration of MO in solution at different time intervals during the photodegradation experiment. Parameters affecting the photodegradation rate such as catalyst crystallinity, concentration of the catalyst, MO concentration, and pH of the solution have been investigated. The results indicate that TiO₂ nanopowder was antase at low calcination temperatures in the range of 400-500 °C. The sample calcined at 600 °C is composed of both anatase and rutile phase. Further increase in the temperature enhanced the intensities of diffraction peaks of the rutile phase. The size of the crystallites for all the samples prepared were found to be in the 6-13 nm range and from SEM micrographs it was in the range of 19-43 nm. The mixture of both phases exhibited a higher photoactivity in comparison with pure anatase or rutile catalysts.