Kinetic study of ketones photocatalytic oxidation in gas phase using TiO2-containing paper: effect of water vapor

Photocatalytic oxidation of two ketones, acetone, and 2-butanone, over TiO2-containing paper was studied under two different levels of relative humidity. Adsorption of these ketones on TiO2-containing paper is significantly affected by the presence of water vapor. Adsorption isotherms of both acetone and 2-butanone, under dry and humid atmosphere, can be satisfactory described using the Langmuir adsorption model for concentrations ranging from 0 to 6 g m−3. Kinetic data of the photocatalytic oxidation of these ketones are analyzed using the Langmuir–Hinshelwood model except for the photocatalytic oxidation of acetone in humid air conditions where adsorption was assumed to be the rate limiting step. In the case of acetone, photoactivity is greatly inhibited in presence of water vapor. On the other hand, it is showed that water vapor has little effect on 2-butanone photocatalytic degradation. The latter is just slightly improved in humid air conditions for initial 2-butanone concentrations upper than 2 g m−3. An explanation is given in term of adsorption affinity of the pollutants compared with competitive adsorption of water molecules with the ketones onto TiO2-containing paper.