Síntese, caracterização e avaliação de novos nanocompósitos híbridos como carreadores para liberação controlada de pesticidas
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Data
2019-10-11
Autores
Tanaka, Fabrício Cerizza
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Universidade Estadual Paulista (Unesp)
Resumo
Com o objetivo de aplicar agroquímicos de uma forma controlada, e reduzir os danos à saúde e ao meio ambiente causados por estes, foram desenvolvidos neste trabalho, dois novos hidrogéis a partir de dois polissacarídeos diferentes carboximetilcelulose (CMC) e quitosana (Qs), suportados em redes de poli (ácido metacrílico)-co-poliacrilamida (PMAA-co-PAAm). Também foi investigada a influência da zeólita nas principais propriedades agroquímicas desses materiais como sorção e dessorção de herbicidas. A estabilidade da zeólita na solução polimérica foi estudada por meio de medidas de viscosidade. Estes comprovaram que a adição de polissacarídeo na solução formadora dos hidrogéis possibilita a obtenção de um hidrogel nanocompósito homogêneo. A incorporação da zeólita nos hidrogéis foi confirmada pela presença das bandas características da zeólita em 798 cm-1 e 600 cm-1 nos espectros de FTIR dos hidrogéis nanoestruturados. Outros indícios de incorporação foram a redução no volume dos poros e a presença de microporos nas paredes dos poros dos hidrogéis, aumento na massa residual dos hidrogéis nanoestruturados a 800ºC, observados nos resultados obtidos por microscopia eletrônica de varredura (MEV) e análise termogravimétrica (TG), respectivamente. Constatou-se também que a presença da zeólita reduziu o grau de intumescimento desses materiais, devido ao decréscimo na elasticidade das cadeias poliméricas. Entretanto, nos resultados de dessorção observou-se que a presença da zeólita pode auxiliar no controle da quantidade de herbicida liberada, e que os hidrogéis desenvolvidos neste trabalho, liberaram o herbicida difenzoquat de uma forma lenta. Os resultados de dessorção em meio salino mostram que os hidrogéis estudados neste trabalho podem reduzir a presença de íons Al+3, no qual, em solos com pH ácidos são nocivos para algumas cultura. Esses resultados indicam que além de liberar defensivos agrícolas, o uso do hidrogel na agricultura pode reduzir custos relacionados com a neutralização do solo.
In order to apply agrochemicals in a controlled manner, and to reduce the damages to the health and environmental caused by these, two new hydrogels based on carboxymethylcellulose (CMC) and chitosan (Qs) polysaccharides supported on poly(methacrylic acid)-co-polyacrylamide (PMAA-co-PAAm) networks were synthesized. The influence of zeolite on the main properties of these materials such as sorption and desorption was also investigated. The stability of zeolite in the polymeric solution was studied by viscosimetry. These results showed that the addition of polysaccharide in the hydrogel-forming solution enables the obtaining of homogeneous nanocomposite hydrogels. The incorporation of zeolite into hydrogels was confirmed by the presence of spectroscopic bands at 798 cm-1 and 600 cm-1 in the FTIR nanocomposite spectra. Other indicatives were the reduction in pore volume and the presence of micropores in the pore walls of zeolite hydrogels, and increase in the residual mass of nanostructured hydrogels at 800ºC, observed by scanning electron microscopy (SEM) and thermogravimetric analysis (TG), respectively. It was also observed that the presence of zeolite reduced the degree of swelling of these materials, due to the decrease in the elasticity of the polymeric chains. The results of desorption in saline medium show that the hydrogels studied in this work can reduce the presence of Al+3 ions, which in acidic soils are harmful to some crops. These results indicate that the hydrogel nanocomposites can be simultaneously used as carrier vehicles in agrochemicals controlled release and as materials to reduce the costs of the soil neutralization.
In order to apply agrochemicals in a controlled manner, and to reduce the damages to the health and environmental caused by these, two new hydrogels based on carboxymethylcellulose (CMC) and chitosan (Qs) polysaccharides supported on poly(methacrylic acid)-co-polyacrylamide (PMAA-co-PAAm) networks were synthesized. The influence of zeolite on the main properties of these materials such as sorption and desorption was also investigated. The stability of zeolite in the polymeric solution was studied by viscosimetry. These results showed that the addition of polysaccharide in the hydrogel-forming solution enables the obtaining of homogeneous nanocomposite hydrogels. The incorporation of zeolite into hydrogels was confirmed by the presence of spectroscopic bands at 798 cm-1 and 600 cm-1 in the FTIR nanocomposite spectra. Other indicatives were the reduction in pore volume and the presence of micropores in the pore walls of zeolite hydrogels, and increase in the residual mass of nanostructured hydrogels at 800ºC, observed by scanning electron microscopy (SEM) and thermogravimetric analysis (TG), respectively. It was also observed that the presence of zeolite reduced the degree of swelling of these materials, due to the decrease in the elasticity of the polymeric chains. The results of desorption in saline medium show that the hydrogels studied in this work can reduce the presence of Al+3 ions, which in acidic soils are harmful to some crops. These results indicate that the hydrogel nanocomposites can be simultaneously used as carrier vehicles in agrochemicals controlled release and as materials to reduce the costs of the soil neutralization.
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Palavras-chave
Hidrogel, Polissacarídeo, Zeólita, Dessorção, Herbicidas, Nanocompósitos, Hydrogel, Polysaccharide, Zeolite, Desorption, Herbicides, Nanocomposites