Micro-sized TiO2 photocatalyst for the purification of air from acetone and acethaldeide

In the last years increasingly restrictive regulations about the concentration limit of pollutants in air enhanced the development of more efficient treatment processes. In particular, advanced oxidation processes (AOPs) are chemical oxidation technologies that rely on the formation of the hydroxyl radical (OH˙) to further oxide organic contaminants which are completely mineralized or converted to less harmful products. AOPs based on UV radiation involve photocatalysts, such as titanium dioxide (TiO2) mostly in nanometric size. However, nanoparticles give rise to many problems such as the catalyst-recovering, hindering their commercial application, other than possible damages on both human safety and environment. The present paper reports a comparative study on the application of nano (P25 by Evonik) and micro-sized (1077 by Kronos) TiO2 samples as photocatalyst on degradation of acetone (AC) and acetaldehyde (AD). Photocatalytic degradations of both pollutants were performed in a Pyrex glass cylindrical reactor of 5 L with 0.05 g of photocatalyst. The gaseous mixture in the reactor was obtained by mixing hot chromatographic air, humidified at 4, 40 and 75%, and an initial concentration of pollutant of 400 ppmV verified by an online micro-GC. The irradiation is carried out by an iron halogenide lamp (Jelosil, model HG 500) emitting in the 315-400 nm wavelength range (UV-A) with power of 30 W/m2. As shown in Fig. 1 the activity of the micro-TiO2 is comparable with that of the nano-sized one even if it is a little bit slower. In both cases, micro-GC analyses detected the formation of CO2 after the degradation: experimental results indicate the formation of CO2 at 100%, confirming a full degradation of the starting molecule (acetone).Considering these outcomes, the employment of microsized TiO2 as a photocatalyst turns out to be a valid alternative to the nano-sized catalysts. Moreover, in order to complete this study, TiO2 samples have been also doped with F to verify the influence of such a dopant on the material photoefficiency.