Effect of calcination temperatures on the photocatalytic activities of commercial titania nanoparticles

Titania (Ti02) has been one of the most studied photocatalysts due to its high activity. Special attention has been focused on the use of Ti02 nanoparticles since the nanoparticles usually show higher photocatalytic activity than the bulk particles .1-3 However, in order to get active photocatalysts, both particle size and crystallinity should be optimized. In this study, effect of calcinat ion temperatures on the photocatalytic activities of four commercial Ti02 nanoparticles was investigated by studying both particle size and crystallinity. Four commercial Ti02 photocatalysts, which were Evonik P25, Evonik P90, Hombikat UV100, and Hombikat N100 were calcined at 573 or 773 K for 4 hours. The samples were characterized by X-ray diffraction (XRO) and transmission electron microscope (TEM). The XRO and TEM results showed that calcination temperatures increased the crystallinity and size of Ti02, especially UV100. The photocatalytic activity of the samples was evaluated for the degradation of 2,4-d ichlorophe noxyacetic acid (2,4-0 ) herbicide under UV light irradiation for 1 hour. The activity of P25 and P90 was slightly improved when the photocatalysts were calcined at 573 K, but decreased when calcined at 773 K. On the other hand, Hombikat catalysts showed an improved activity with the increase of calcination temperatures. The largest improvement can be observed on the UV100 due to the largest increase on the crystall inity and size as shown in Fig 1. The different behaviour of the Ti02 nanoparticles demonstrated that the optimum calcination temperature should be investigated for each Ti02 nanoparticles before it is further modified