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 beta 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 a- 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 NO - 3 were detected as advanced oxidation products.