Photocatalytic destruction of organic dyes by titanium dioxide particles doped with gold

Nanocomposites based on titanium dioxide doped with gold in concentrations of 0.2 and 0.8 wt.% were obtained by the sol-gel method using titanium tetraisopropoxide and chlorauric acid. Thermal treatment of precipitates at T = 600 °C led to the formation of highly dispersed anatase powders and increasing the temperature to 1000-1200 °C contributed to the formation of well-crystallized rutile particles. The gold in the structure of the powders is heterogeneously distributed. The size of the primary particles of anatase did not exceed 10 nm, and that of rutile reached 35-46 nm, gradually increasing with increasing processing temperature. The photocatalytic properties of TiO2&Au structures were studied during the decolorization of solutions of organic dyes (Methylene Blue, Rhodamine B, Methyl Orange, Orange G) with a concentration of 20 mg/dm3. The resulting structures did not show significant sorption activity, and visible light caused a slight desorption of the dyes. At the same time, under the influence of UV irradiation for 60 minutes, the decolorization process took place effectively and was subject to a pseudo-first-order reaction. The biggest photocatalytic activity was shown by the sample of anatase with a gold content of 0.8 wt.%. When it was added into the solution, the degree of decolorization of Rhodamine B reached up to 50%, Methyl Orange - up to 81.5%, Methylene Blue - up to 91%, and Orange G - up to 95.2%. Increasing the efficiency of the destruction of dyes can be achieved by supplementing the photo-catalytic process with a catalytic one.   Аcknowledgements : Olena Lavrynenko is supported by the PAUSE program, a national emergency program for scientists and artists in exile, run by the Collège de France