Comparison between the reactivity of commercial and synthetic TiO2 photocatalysts

Titanium dioxide in powder form is largely used as a catalyst in the field of detoxification of aqueous effluents by photocatalysis. One of the most efficient commercial photocatalysts is TiO2/P25 manufactured by flame hydrolysis. In this work, we compare the reactivity between this commercial TiO2/P25 and a synthetic photocatalyst TiO2/SG prepared in our laboratory by sol-gel method. The photocatalytic activities of TiO2/P25 and TiO2/FG were tested using a benzamide solution. We have noticed that the total organic carbon (TOC) evolution of the benzamide solution during the photodegradation was different between both photocatalysts (when the kinetic evolution of benzamide are similar). There is a slower decrease for TOC in the case of the TiO2 synthetized by sol-gel method. The results of the adsorption and photodegradation experiments explain this difference between the two photocatalysts. As a matter of fact, it is known that the degradation rate depends on the capacity of the molecules to adsorb at the catalyst surface. So, we have pointed out that this adsorption capacity is lower in the case of TiO2/SG. This explains the degradation rates found. And since the TOC variation depends on the intermediate degradation rate and not on the benzamide, it seems normal to note a lower evolution for the TOC in accordance with the irradiation times. (C) 2001 Elsevier Science B.V. All rights reserved.