Photocatalytic degradation kinetics and mechanisms of fungicide tebuconazole in aqueous TiO2 suspensions

The photocatalytic degradation of tebuconazole (TEB), a common fungicide with numerous agricultural and urban uses, has been investigated under simulated solar irradiation. Response surface methodology (RSM) was employed to assess individual and interactive effects of the three main independent parameters (initial TEB concentration, irradiation intensity and catalyst concentration) on the efficiency of the process. Optimization results showed that maximum TEB degradation and TOC removal was achieved at the optimum conditions: C-TEB = 1 mg L-1, C-TiO2 - 550 mg L-1, I=650 W m(-2). By means of high resolution accurate mass liquid chromatography (HR-LC-MS) and gas chromatography-mass spectroscopy (GC-MS) nine transformation products were identified. The transformation of TEB pathways was found to proceed through tert-butyl chain cleavage, hydroxylation, oxidation and dechlorination pathways. Scavenging experiments showed that the degradation mechanism of TEB was mainly driven by HO center dot and h(+). Finally, the application of an acute toxicity test (Vibrio fischeri) to selected water samples resulted in a non-inhibitory effect of the bacterial bioluminescence. (C) 2014 Elsevier B.V. All rights reserved.