Nanocrystalline TiO 2 was synthesized by controlled hydrolysis of titanium tetraisopropoxide. The anatase phase was converted to rutile phase by thermal treatment at 1023 K for 11 h. The catalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), Fourier-transform infrared absorption spectrophotometry (FT-IR) and N 2 adsorption (BET) at 77 K. This study compare the photocatalytic activity of the anatase and rutile phases of nanocrystalline TiO 2 for the degradation of acetophenone, nitrobenzene, methylene blue and malachite green present in aqueous solutions. The initial rate of degradation was calculated to compare the photocatalytic activity of anatase and rutile nanocrystalline TiO 2 for the degradation of different substances under ultraviolet light irradiation. The higher photocatalytic activity was obtained in anatase phase TiO 2 for the degradation of all substances as compared with rutile phase. It is concluded that the higher photocatalytic activity in anatase TiO 2 is due to parameters like band-gap, number of hydroxyl groups, surface area and porosity of the catalyst.

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This present work focuses on the photocatalytic activity of Fe(III) salt-impregnated TiO 2 catalysts for studying the effect of anion on the photocatalytic activity of the salt-impregnated catalysts. The salt-impregnated TiO 2 photocatalyst samples prepared using FeCl 3 , Fe(NO 3 ) 3 , and Fe 2 (SO 4 ) 3 were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectrophotometry (DRS), Fourier transform infrared absorption spectrophotometry (FT-IR), and surface area measurement by N 2 adsorption. Fe(III) ion impregnation of TiO 2 with different salts is observed to influence photocatalytic degradation of acetophenone. Fe(III) salt anions were observed to influence the initial rate of degradation. For example, the initial rate of degradation of acetophenone decreases with an increase in percentage of Fe(III) ions in the case of the catalysts prepared using ferric nitrate and ferric chloride salts. However, the initial rate of degradation was observed to increase with ferric sulfate impregnated catalysts. The final percentage degradation of acetophenone was found to increase continuously with an increase in Fe(III) ion concentration, irrespective of the anion. These observations have been discussed in terms of influence of the presence of Fe(III) ions on the recombination of the electron and holes generated during UV irradiation of TiO 2 . Similarly, the effect of anion has been discussed in terms of radical-scavenging ability of chloride and radical-generating ability of sulfate anions.