Naveetha Gaggara^1,, Atmakuru Ramesh¹

The present research describes the photo catalytic degradation of Bispyribac sodium, a pyrimidinyloxybenzoic herbicide, widely used in the protection of the paddy field. The degradation was investigated in an aqueous suspension using ZnO/Na2S2O8 as the photo sensitizer / oxidant. Photocatalysis of bispyribac sodium was studied in three different aqueous buffer solutions (pH 4, 7 and 9) under direct sunlight. Liquid Chromatography Electro spray Tandem Mass spectrometry (LC-MS/MS) was used to identify the major photo transformation products in water. In this present study we also investigated the effect of bispyribac sodium and its breakdown products on the growth of green alga (Pseudokirchneriella subcapitata). The results showed that the addition of a photosensitizer was strongly enhancing the elimination of pesticides when compared to photolysis tests. This process also enhances the reaction rate very rapidly. The addition of the oxidant (Na2S2O8) with the ZnO increases the rate of reaction has the added advantage over the ZnO alone. The degradation of the bispyribac Sodium follows first order kinetics. Green alga growth rates (Er) and yield percentage (Ey) were determined statistically. Initially, the growth rate inhibition was very high after that the inhibition was decreased while increasing the irradiation Time.

zinc oxide, nanoparticles, oxidant, photosensitizer, herbicide, Green alga