Influence of adsorption on the photocatalytic properties of TiO2/AC composite materials in the acetone and cyclohexane vapor photooxidation reactions

Abstract

► A series of TiO 2 /AC photocatalysts with different TiO 2 contents were synthesized. ► Acetone and cyclohexane vapor photooxidation were studied in static and flow reactors. ► Adsorptivity of TiO 2 /AC catalysts was increased and activity decreased in the sequence TiO 2 , TiO 2 /AC, TiO 2 + AC. ► Reagents surface transfer is responsible for increase of TiO 2 /AC photoactivity. A series of TiO 2 /AC composite photocatalysts with various TiO 2 contents was prepared by thermal hydrolysis method of a TiOSO 4 water solution in the presence of activated carbon particles. XRD, SEM and BET methods revealed that in all cases deposited TiO 2 is an anatase with ∼170 m 2 /g specific surface area. All samples were tested in gaseous acetone and cyclohexane vapor photocatalytic oxidation in static and continuous flow reactors. Complete photocatalytic mineralization of both model pollutants without formation of gaseous intermediates was observed. Only TiO 2 /AC catalysts with TiO 2 content higher than 50% demonstrated good photocatalytic activity. The same amounts of individual TiO 2 and AC powders as in the case of 70%-TiO 2 /AC composite photocatalyst were placed separately in the static reactor and kinetic curves of the cyclohexane photocatalytic oxidation were compared for both cases. When TiO 2 and AC were used separately complete mineralization of cyclohexane was not observed even after 4 h of the PCO. Whereas in the case of 70%-TiO 2 /AC sample expected CO 2 level was almost achieved after 120 min. The most likely reason of this difference is the absence of reagents and intermediates surface transfer between separated individual TiO 2 and AC powders. L.-H. kinetic model was used to describe experimental data in the flow reactor. Obtained results demonstrated that effective adsorption constants for TiO 2 /AC photocatalysts were about 2 times higher than for pure TiO 2 . Model of TiO 2 /AC composite photocatalyst with increased photocatalytic and adsorption properties was suggested.