Estudo da complexação do pesticida picloram com o íon metálico ferro por medidas eletroquímicas
Data
2022-06-23
Autores
Rodrigues, Nataly Ireonio Cruz 
Orientadores
Akamatu, Eliana Maíra Agostini Valle
Tipo
Trabalho de conclusão de curso
Título da Revista
ISSN da Revista
Título de Volume
Resumo
À medida que a sociedade cresceu e se desenvolveu, surgiu a necessidade de se
fazer uso de substâncias, conhecidas por pesticidas, para aumentar a produtividade
de alimentos, bem como garantir seu armazenamento. A prática de uso dessas
substâncias, faz com que ocorra acúmulo dos mesmos no ambiente, causando
consequências graves. Tais substâncias, ao entrar em contato com diferentes
espécies no ambiente, podem interagir e alterar suas propriedades. Um pesticida
comum e que é amplamente utilizado, é o picloram, um herbicida da família dos
organoclorados que possui uma alta persistência no ambiente e, devido a sua
estrutura química, pode formar complexos com íons metálicos. Tendo em vista que o
ferro é um dos elementos mais abundantes da crosta terrestre, neste trabalho avaliou-
se as técnicas de voltametria cíclica e voltametria de onda quadrada para estudar a
complexação do picloram com o íon metálico ferro. O Fe (III) apresentou pico de
redução em 0,0 V, em um processo controlado pela difusão das espécies sobre a
superfície do eletrodo, e nas condições utilizadas para esse estudo, apresentou
características de um sistema irreversível. Na voltametria cíclica, o Fe (III) quando em
presença de picloram, apresentou uma diminuição na intensidade de pico e
deslocamento para potenciais menos positivos, e o complexo Fe (III) – picloram
demonstrou ser um processo de controle misto. Na voltametria de onda quadrada,
observou-se um aumento na intensidade de pico e um deslocamento do pico de
redução do Fe (III) de 0,060 V para 0,103 V. Na espectroscopia de UV-visível, o
picloram mostrou banda em 223 nm, e na presença de Fe (III) apresentou aumento
na intensidade de absorção e comprimento de onda. Observou-se também um
aparecimento de um braço em 282 nm com o aumento da concentração de Fe (III).
As society grew and developed, the need arose to make use of substances, known as pesticides, to increase food productivity, as well as ensure its storage. The practice of using these substances causes their accumulation in the environment, causing serious consequences. Such substances, when in contact with different species in the environment, can interact and change their properties. A common pesticide that has been widely used is picloram, an organochlorine herbicide that has a high persistence in the environment and, due to its chemical structure, can form complexes with metal ions. Bearing in mind that iron is one of the most abundant elements in the earth's crust, in this work the techniques of cyclic voltammetry and square wave voltammetry were evaluated to study the complexation of picloram with the metallic iron ion. Fe (III) showed a reduction peak at 0.0 V, in a process controlled by the diffusion of the species over the electrode surface, and under the conditions used for this study, it showed characteristics of an irreversible system. In cyclic voltammetry, Fe (III) when in the presence of picloram, showed a decrease in peak intensity and shift to less positive potentials, and the Fe (III) – picloram complex showed to be a mixed control process. In square wave voltammetry, an increase in peak intensity and a shift of Fe (III) reduction peak from 0.060 V to 0.103 V were observed. In UV-visible spectroscopy, picloram showed a band at 223 nm, and in the presence of Fe (III) it showed an increase in the absorption intensity and wavelength. An appearance of an arm at 282 nm was also observed with increasing Fe (III) concentration.
As society grew and developed, the need arose to make use of substances, known as pesticides, to increase food productivity, as well as ensure its storage. The practice of using these substances causes their accumulation in the environment, causing serious consequences. Such substances, when in contact with different species in the environment, can interact and change their properties. A common pesticide that has been widely used is picloram, an organochlorine herbicide that has a high persistence in the environment and, due to its chemical structure, can form complexes with metal ions. Bearing in mind that iron is one of the most abundant elements in the earth's crust, in this work the techniques of cyclic voltammetry and square wave voltammetry were evaluated to study the complexation of picloram with the metallic iron ion. Fe (III) showed a reduction peak at 0.0 V, in a process controlled by the diffusion of the species over the electrode surface, and under the conditions used for this study, it showed characteristics of an irreversible system. In cyclic voltammetry, Fe (III) when in the presence of picloram, showed a decrease in peak intensity and shift to less positive potentials, and the Fe (III) – picloram complex showed to be a mixed control process. In square wave voltammetry, an increase in peak intensity and a shift of Fe (III) reduction peak from 0.060 V to 0.103 V were observed. In UV-visible spectroscopy, picloram showed a band at 223 nm, and in the presence of Fe (III) it showed an increase in the absorption intensity and wavelength. An appearance of an arm at 282 nm was also observed with increasing Fe (III) concentration.