Degradación de carbofurano, paraquat y clorpirifos por procesos de oxidación avanzada

Abstract

Water is an essential resource to conserve the life of all beings that inhabit the planet and has been affected by the indiscriminate use of toxic pesticides. According to the commercialization statistics of chemical pesticides for agricultural use reported by the Colombian Agricultural Institute (ICA), in 2016 in our country a total of 57’284.087 liters of pesticides were sold, among which stand out the paraquat with 4'471.787 , mancozeb with 2’764.047, chlorpyrifos with 2’197.095 and carbofuran with 126.21 L (Table 1); These pesticides have high toxicity to mammals and all non-target animals present in ecosystems. The excessive and indiscriminate use of low biodegradable pesticides used in the control of pests in the country, has increased the production of leachates; Because a large part of them do not remain in the crop, they seep through the soil and contaminate the aquifers. That is why in the present investigation heterogeneous photocatalysis was used as an advanced oxidation method to degrade carbofuran, paraquat and chlorpyrifos, which are pesticides widely used in various crops implemented in Colombia, such as potatoes, sugar cane , coffee, onion, corn, among others. During this process, tetraphenylporphyrin chlorine (TClPP) and tetraphenylporphyrin methoxy (TMeOPP) were synthesized and metallized with iron (III) through condensation and coordination reactions reported in the literature (Adler et al., 1967; Falvo et al 1999). Porphyrins were then supported on titanium dioxide (TNT) nanotubes, which were prepared by hydrothermal reaction, which is based on an alkaline treatment of a titanium oxide precursor (Wu, et al., 2015). As a result, the modifications made to commercial titanium dioxide generated an increase in the production of oxidizing species when subjected to UV-Vis radiation, as well as the extension of semiconductor activation to the visible range. Catalysts sensitized with free porphyrins TClPP/TNT and TMeOPP/TNT degraded carbofuran in 83% and 85%; paraquat in 67% and 76%; and chlorpyrifos in 73% and 78%, respectively. The inclusion of iron as the metal center of the catalysts increased the average degradation percentage as follows: with the use of TClPPFe/TNT, it was possible to degrade carbofuran, paraquat and chlorpyrifos in 95%, 85% and 84% respectively, and through using the TMeOPPFe/TNT a percentage of carbofuran degradation of 89%, paraquat 82% was obtained; and chlorpyrifos 84%.