Kinetical Study of the Photoinduced Degradation of Imidacloprid in Aquatic Media

Abstract

The photoinduced degradation of the insecticide imidacloprid in natural water samples was performed in order to describe its abiotic degradation. Numerous degradation products could be identified with the help of spectroscopic methods. The main photoproducts were 1-[(6-chloro-3-pyridinyl)methyl]-N-nitroso-2-imidazolidinimine, 1-[(6-chloro-3-pyridinyl)methyl]-2-imidazolidinimine (which is known to be more toxic for warm-blooded animals than imidacloprid) and 1-[(6-chloro-3-pyridinyl)methyl]-2-imidazolidinone. Besides numerous other degradation products, 6-chloro-nicotineamide was identified as the end product of the photolytic reaction. The photoinduced reaction of imidacloprid followed pseudo first-order reaction kinetics and resulted from a triplet-controlled intermediate state with a triplet energy between 281 -290 kJ/mol and an half-life time of 4.6610 -9 s. With the help of measured quantum yields (U S ), the half-life time of imidacloprid in natural waters was estimated at 3 days. The calculated half-life times of 1-[(6-chloro-3-pyridinyl)methyl]-2-imidazolidinimine was much shorter, 0.24 days, while those of 1-[(6-chloro-3-pyridinyl)methyl]-2-imidazolidinone and 6-chloro-nicotine-amide were higher at 270 and 660 days, respectively.

Ionic‐Liquid‐Assisted Hydrothermal Synthesis of Ag/AgBr for Photodegradation of Imidacloprid under Visible Light

“…It could be concluded that imidacloprid was subjected to a series of redox reactions under the action of light and catalyst. The final result was the degradation of imidacloprid into small molecules, CO 2 , and H 2 O, which corresponds to previous relevant literature …”

Modeling photodegradation kinetics of three systemic neonicotinoids—dinotefuran, imidacloprid, and thiamethoxam—in aqueous and soil environment

“…Enhanced photolysis of imidacloprid has been observed with the addition of photosensitizers such as TiO 2 , whereas the addition of acetone appears to inhibit photolysis . Stability of imidacloprid in natural waters irradiated with a mercury high‐pressure lamp shows that imidacloprid exhibits pseudo first‐order reaction kinetics with an estimated half‐life of 3 d . Similar results have been reported by other researchers stating that pseudo first‐order rate constants are inversely related to concentration .…”

CeO2 for Water Remediation: Comparison of Various Advanced Oxidation Processes

“…The reaction mechanism involves the breaking of C-N and the N-N bonds followed by the formation of small molecules, such as chlorine dioxide, nitrogen oxides species, water and carbon dioxide [7,54,55]. The reported degradation percentage of IMI (i.e., the variation of the IMI concentration respect to the initial IMI concentration) was low even through photocatalysis [54][55][56], solar photo-Fenton [57], or UV-A photolysis [28]. In particular, with UV irradiation it is possible to obtain a complete photolysis of IMI after a long time of irradiation (about 10 h) [28], whereas in our precedent work [7] with molecularly imprinted TiO 2 samples, it was possible to selectively photodegrade IMI even in a pesticide mixture, although the degradation efficiency did not exceed 40% with a partial mineralization of~35% (evaluated by the Total Organic Carbon, TOC, analysis) after 3 h of UV irradiation.…”