Intercalação de insecticidas malatião, fenitrotião e pirimifos metílico em argila bentonite de Boane

Abstract

The World Health Organization (WHO) estimates that 300 to 500 million cases of malaria are reported annually worldwide. Intradomiciliary spraying is one of the strategies used by WHO to combat malaria. Of all the insecticides approved by WHO for use in the fight against malaria, twelve, DDT is the most efficient and most economical. However, due to its persistence, it tends to create damage to the environment. For this reason, several countries are abolishing its use in public health programs but Mozambique is one of the countries that still uses DDT. The other insecticides, although not very persistent, are more susceptible to environmental effects, which would mean additional costs to health programs. One way to solve the problem would be to protect the insecticide from environmental effects and allow its controlled release. Clays have a stratified structure that can be expanded to accommodate insecticide molecules, for example. The present work presents the intercalation of organophosphate insecticides with Boane bentonite clay. Organophosphate insecticides have a low persistence when compared to organochlorines, hence their choice. To proceed with intercalation, the initially crude clay was purified with hydrochloric acid, later made sodium using sodium carbonate. The sodium clay thus obtained was intercalated by the direct method, by heating to 20 ° C the clay-insecticide mixture under stirring. The characterization of the clays: crude, purified with acid, sodium, after treatment and after 6 months, was performed by the IR technique. FT-IR analyzes carried out indicated the presence of the insecticide within the clay. The results obtained shortly after the preparation of the formulations indicated that the insecticide suffered degradation. This conclusion is based on the absence of the band corresponding to the main link of organophosphate insecticides, the link P = S, for the case of phenitrothion and malathion. For pyrimiphos-methyl, the strong presence of the bands of the methyl (CH 3) and methylene (CH 2) groups was observed and also by the absence of the P = S bond. The results obtained in this work suggest that the insecticides phenitrothion, malathion and methyl pyrimiphos degraded 3-methyl-4-nitrophenol, malaoxon and 2-diethylamino 4- hydroxy-6-methylpyrimidine respectively. These products were obtained mainly due to the heating in the intercalation process.(TRADUÇÃO NOSSA)