Applications of Zinc Oxide Nanorods as Photocatalyst for the Decontami- nation of Imidacloprid and Spirotetramat Residues in Water

Zinc oxide nanorods having the size 100 to 250 nm and 1 to 2 m length were prepared by reacting zinc acetate with triethanolamine. The structure of the nanorods was confirmed by scanning electron microscope analysis. Photocatalytic activity of zinc oxide nanorods on the new class of ketoenole and chloronicotinyl insecticides spirotetramat and imidacloprid was investigated. The decontamination effect of catalyst on the residues of spirotetramat and imidacloprid in water was studied at three different buffer solutions (4.0, 7.0 and 9.0). The catalytic reaction was measured under direct sunlight at two different concentration levels and the optimum concentration of catalyst required for the decontamination was also established by varying the amount of catalyst from 0.02 to 0.2 g/L. Residues are quantified by a high performance liquid chromatography UV method (HPLC-UV) and calculated the DT 50 and DT 90 from the dissipation data. The rate of the reaction showed first order kinetics in water. The addition of zinc oxide nanorods induced the photocatalytic reaction contributing significantly to the rapid dissipation of residues. Complete mineralization of the residues was confirmed by liquid chromatography electrospray tandem mass spectrometry (LC-ESI-MS/MS). The method has the limit of quantification 0.1 g/L in water.