Affiliations: Institute of Environmental Science, Zhejiang
University, Hangzhou 310027, China | Department of Environmental Sciences, University of
California, Riverside, CA 92521, USA | Louisiana Water Resources Research Institute,
Louisiana State University, Baton Rouge, LA 70803, USA
Abstract: The direct and sensitized photodegradations of imidacloprid,
1-(6-chloro-3-pyridinylmethyl)-N-nitro-2-imidazolidinimine. were investigated
in aqueous solution and with and without various photo-sensitizers. Results of
the study revealed that the intensity of lamp-house and irradiation wavelength
had significant effects on the photolysis of imidacloprid. Complete degradation
of 20 mg/L imidacloprid in aqueous phase was observed in 40 min under
ultraviolet (UV) irradiation system, suggesting the ultraviolet ray played
significant role in direct photolysis of imidacloprid. The additions of various
photo-sensitizers lead to improve the degradation efficiency of imidacloprid
under the irradiation of black light fluorescent lamp. TiO_2
was the most efficient in the photo-catalytic degradation of imidacloprid among
other photo-sensitizers in used this study. However, addition of acetone
inhibited the photolysis of imidacloprid under the irradiation of UV,
indicating the occurrence of competition between acetone and imidacloprid for
photos. Mineralization of the imidacloprid was examined to clarify the final
photochemical degradation products of the insecticide which were
CO_2, Cl^- and NO_3^-.
Complete photo-oxidation of nitrogen to NO_3^- occurred very
slowly via the intermediate formation of NH_4^+ and
NO_2^-.
