Photocatalytic degradation of chlorpyrifos in aqueous suspensions using nanocrystals of ZnO and TiO2

The photocatalytic degradation of an organophosphorus insecticide chlorpyrifos (O,O-diethyl O-3,5,6-trichloro-2 pyridyl phosphorothioate) in aqueous suspensions of nano ZnO and nano TiO2 under sunlight is reported in this study. Nanocrystals of ZnO (34.3 nm) were prepared by the wet chemical method and TiO2 nanocyrstals (7.5 nm) were synthesized from titanium tetraisopropoxide by hydrolysis and peptization. The synthesized nanocrystals were characterized by X-ray diffraction, FT-IR, SEM-EDS and UV-Visible analytical techniques. The degradation of the insecticide was studied by monitoring the change in substrate concentration employing UV-Visible spectroscopy. The influence of catalyst loading, substrate concentration and pH were studied. The intermediates of the degradation process were identified by GC-MS. The synthesized nano ZnO and nano TiO2 demonstrated high photocatalytic activity under solar light. The results show that nanocrystals of TiO2 exhibit a better photocatalytic activity on the degradation of Chlorpyrifos than nanocrystals of ZnO.