Syntheses of TiO2 photocatalysts by the molten salts method: Application to the photocatalytic degradation of Prosulfuron®

Titania photocatalysts were synthesised by the molten salts method by reaction of a titanium precursor with three different alkali metal nitrates (LiNO3, NaNO3, KNO3). The titania powders obtained have been characterised using TEM, XRD, BET and UV-Vis absorption spectroscopy. Their photoactivities were evaluated by degrading a commercial sulfonylurea herbicide, Prosulfuron®. It has been found that the rate constants increased in the following order: Li<Na<K. The best results were obtained for TiO2 prepared in KNO3, with a rate constant 1.4 times smaller than that of P25. The effect of calcination was also studied, especially for the sample prepared in NaNO3 (TiO2[Na]). An improvement in photocatalytic activity was observed when TiO2[Na] was calcined in the region of 700–800 °C. Even though the photocatalytic activities obtained did not exceed or even equal to that of Degussa P25, nevertheless, this study constitutes the first attempt to synthesise titania photocatalysts by the molten salts method.