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

A series of TiO2/AC composite photocatalysts with various TiO2 contents was prepared by thermal hydrolysis method of a TiOSO4 water solution in the presence of activated carbon particles. XRD, SEM and BET methods revealed that in all cases deposited TiO2 is an anatase with ∼170 m2/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 TiO2/AC catalysts with TiO2 content higher than 50% demonstrated good photocatalytic activity. The same amounts of individual TiO2 and AC powders as in the case of 70%-TiO2/AC composite photocatalyst were placed separately in the static reactor and kinetic curves of the cyclohexane photocatalytic oxidation were compared for both cases. When TiO2 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%-TiO2/AC sample expected CO2 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 TiO2 and AC powders. kinetic model was used to describe experimental data in the flow reactor. Obtained results demonstrated that effective adsorption constants for TiO2/AC photocatalysts were about 2 times higher than for pure TiO2. Model of TiO2/AC composite photocatalyst with increased photocatalytic and adsorption properties was suggested.