Effects of operational parameters on the photodegradation of 2,4-dinitrophenol in TiO2 dispersion

Photocatalytic degradation of 2,4-dinitrophenol in two commercial TiO2 (Degussa P25 and Hombikat UV-100) was investigated in this work. The properties of two TiO2 were systematically studied and described in detail. The observed photoactivity of Degussa P25 was 6–12 times higher than Hombikat UV-100 although the specific surface area of Hombikat UV-100 was 5.7 times more than that of Degussa P25. The photodegradation of 2,4-dinitrophenol was favored at neutral pH in Degussa P25, while its degradation was preferred at pH 3.0 in Hombikat UV-100 dispersion. The observed kinetic constant (kobs) for the photodegradation of 2,4-dinitrophenol in 20 mg/L humic acid solution was found to be 15% (Degussa P25) and 21% (Hombikat UV-100) of the values obtained from the corresponding pure aquatic solutions. The suppression effects of β-cyclodextrin on the photodegradation of 2,4-dinitrophenol over Degussa P25 (50%) was much more significant than that of Hombikat UV-100 because of the different adsorption behavior of β-cyclodextrin over two TiO2. Hydroxyl radical and valance band hole was found to be the predominant reactant during the degradation of 2,4-dinitrophenol using P25 and UV-100, respectively. Formic acid, acetic acid, oxalic acid, and were detected as advanced oxidation products.