Photocatalytic and adsorptive treatment of 2,4-dinitrophenol using a TiO2 film covering activated carbon surface

Anatase titanium dioxide (TiO2) in particle sizes of roughly 0.5-20 mu m was prepared from amorphous TiO2 in an aqueous H2O2 solution by heating at 90 degrees C for 9 h and directly deposited on a PET film. On the other hand, granular activated carbon (AC) particles in sizes of 1-2mm in diameter were adhesively deposited on a PET film, and their surfaces were also coated with TiO2. The resulting three preparations (TiO2-, AC-, and TiO2/AC-PET films) were set up in an annular-flow reactor to treat aqueous solutions of 2,4-dinitrophenol (DNP) in a batch-recirculation mode. The rate of DNP adsorption onto the TiO2/AC-PET film without UV irradiation was almost the same as that onto the AC-PET film, indicating that the attraction of DNP to AC was not lowered in the presence of TiO2 film. Observation of SEM photographs suggests that this result is attributed to the porous structure of the thin TiO2 film covering AC particles. The rate of DNP removal by the TiO2-AC PET film under UV irradiation was 2.9 times higher than that by the TiO2-PET film under UV irradiation, and was 1.1 times higher than the rate of DNP adsorption onto the AC-PET film. The rate of DNP removal by the AC-PET film decreased by 40% after six runs, while that by the TiO2/AC-PET film decreased by 22%. Durable experiments using the TiO2/AC-PET and AC-PET films clarified that the lifetime of the TiO2/AC-PET film is at least two times longer than that of the AC-PET film. This result suggests that DNP molecules are photocatalytically decomposed when passing through the porous TiO2-PET film, which lessens a burden of DNP adsorption on AC. Moreover, the DNP treatments in the batch-recirculation flow system suggested that the TiO2/AC-PET film saturated with DNP can be successfully regenerated at 60 degrees C. (C) 2009 Elsevier B. V. All rights reserved.