Intercalação directa dos insecticidas fenitrotião, malatião e pirimifos metílico na bentonite de boane

Abstract

Insecticides are a group of compounds belonging to the class of pesticides. They are widely used in combating disease-causing vectors in humans, animals and plants. These compounds can be applied either alone or combined with others, thus adding their physico-chemical properties. The purpose of this work is to extend the life span of insecticides organophosphates (Phenitrothion, Malathion and Pirimiphos-Methyl), producing an insecticidal formulation bentonite by direct intercalation. The insecticide-bentonite formulation was prepared following the four distinct steps, namely: (i) activation of bentonite, (ii) purification of bentonite, (iii) sodification of bentonite and (iv) direct mixing of an equal amount of insecticides and bentonite. The formulation thus obtained was analyzed by two techniques, thermogravimetric analysis and spectroscopy in the infrared with Fourier transform. Thermogravimetric analysis (ATG) indicated the intercalation of organic compounds in the formulation. The peaks referring to the boiling temperatures of insecticides that should occur, in the ranges of 156-157oC (Malathion) and 140-145oC (Fenitrotião and Pirimifos-Methil). ATG also indicated an effective exchange of Ca 2+ ions by Na + due to the loss of water in the 250-350oC range that corresponds to exchangeable cations in the interlayer of the bentonite. On the other hand, spectroscopic analyzes in the infrared with Fourier transform indicated the insertion of insecticides in bentonite. There is a peak at 706.67cm -1, referring to the stretching vibration of the P = S group in the phenitrothion and intercalated Malathion spectra in sodified bentonite at room temperature and hot. The absence of the signal from the same group, in that wavelength, for Pirimiphos-Methyl interspersed in the sodified bentonite at room and warm temperature suggests that this insecticide has interleaved and adopted a different conformation from the others.(TRADUÇÃO NOSSA)