Active carbon/TiO₂ composites for photocatalytic decomposition of benzoic acid in water and toluene in air

The present work describes the preparations of active carbon (AC) - titania composites with 2 different AC/TiO2 ratios, their characterization using SEM, BET, determination of particle size, and evaluation of adsorption ability and photocatalytic activity using benzoic acid (BA) in the aqueous phase and toluene in the gaseous phase. Composite materials based on AC/TiO2 were prepared from two types of active carbon (having a BET surface area of 1737 m(2) g(-1) and 890 m(2) g(-1), respectively) and TiO2 (P25, BET surface area 45 m(2) g(-1)) by mixing. The main studied parameter was milling of AC. Immobilized photocatalyst films were prepared by drop-casting of aqueous composite suspensions on glass substrates and drying. The composite films prepared from milled AC have much better adhesion to substrate in aqueous media than those from non-milled AC, which is due to a decrease of particle size by about 1 order during milling. The ability of composites prepared from milled AC to remove BA was more than 2.5 times higher than that of composites from non-milled AC. In comparison with TiO2, prepared composites showed similar or higher photocatalytic activity and the irradiation of AC/TiO2 composites in aqueous suspensions resulted in the generation of a comparable concentration of the hydroxyl radical spin-adduct ((DMPO)-D-center dot-OH) as with TiO2.