Síntese, caracterização e aplicação de compostos no sistema Bi2O3: TeO2: Nb2O5 na fotodegradação do agrotóxico clorpirifós.

Abstract

This work presents the results of the evaluation of the photocatalytic activity for the chlorpyrifos degradation using semiconductors synthesized in the Bi2O3:TeO2:Nb2O5 system, being the compositions Bi3NbO7, Bi6Te2O13, and Bi6Te1,8Nb0,2O13. Chlorpyrifos is a toxic pesticide used in many crops, especially grains and is found above the limits allowed in the environment, with a presence especially in surface, groundwater and consumption water. Heterogeneous photocatalysis is evaluated as an alternative to conventional treatment for the degradation of this pesticide in water. For this, the semiconductor oxides were synthesized and characterized by X-Ray Diffraction, Scanning Electron Microscopy, Thermal Analysis and UV/Vis Diffuse Reflectance Spectroscopy. Subsequently, the photocatalytic tests took place in a reactor with 3 UVC lamps (253.7 nm) of 14W each. The three semiconductors were tested in adsorption and photocatalysis assays. Aliquots were removed in order to check the degradation of chlorpyrifos through the technique of high performance liquid chromatography with UV detector (HPLC-UV). The results showed a strong adsorption of chlorpyrifos on the polymers used in the reactor. After removing these materials, the tests were repeated and the results presented show good photocatalytic activity of the semiconductors, despite the microscopic size of the grains, however, the formation of degradation by-products, which could not be identified, strongly interfered with the analytical results, since they possibly leave at the same time as chlorpyrifos in chromatographic analyses.