Aqueous degradation of diclofenac by heterogeneous photocatalysis using nanostructured materials

The photocatalytic degradation of diclofenac (DIC), 2-[2', 6'-(dichlorophenyl)amino]phenylacetic acid is investigated under near UV-Vis and UV irradiation, using commercial TiO2 P25, synthesized TiO2 (anatase and rutile) and functionalized multi-walled carbon nanotube (MWCNTox): anatase (10-MWCNTox-TiO2) suspensions as catalysts. Factors affecting the kinetics of the process, such as the type and load of photocatalyst, and the presence of dissolved O-2, or addition of H2O2 as co-oxidant have been compared. The degradation under UV irradiation is more effective than under near UV-Vis. Optimal conditions fora complete removal were obtained using synthesized anatase (0.5 g L-1) and 50% O-2 (v/v) under UV irradiation, with rate constants ca. 0.9 min(-1) (half-life time ca. 0.8 min). Eight photoproducts were observed from DIC photodegradation, mainly corresponding to photocyclisation (2-(8-chloro-9H-carbazol-1-yl)acetic acid, 1-chloro-8-methyl-9H-carbazole), decarboxylation (2,6-dichloro-N-o-tolylbenzenamine) and dehalogenation. (C) 2011 Elsevier B.V. All rights reserved.