Utilização de lignina para obtenção de formulação e liberação controlada do acido 2,4-diclorofenoxiacetico

AUTOR(ES)
DATA DE PUBLICAÇÃO

1994

RESUMO

Six lignin samples were evaluated for obtaining controlled release formulations of the herbicide 2,4-D (dichlorophenoxyacetic acid). The lignins employed were: Kraft of Eucalyptus obtained from black liquor of the cellulose and paper industry, Kraft from Pinus (Indulin AT) and alkaline lignin extracted from sugar cane bagasse pretreated by steam explosion. The lignins were characterized with regard to elementary analysis, content of functional groups, distribution of molecular mass and spectral characteristics obtaíned trom UV-visible, FTIR and ?H SOB. 1? -NMR. techniques. The formulations were obtained by a herbicide melting process followed by the addition of lignin. Grains having 0,7 to 1,0 mm in diameter were submitted to tests of release in water. The 2,4-D release kinetics was followed by high performance liquid chromatography. The results showed that the kinetíc model that best adapts to the 2,4-D release in water is controlled by diffusion (order 1/2). The . calculated diffusion constants followed the order: kraft lignin from Eucalyptus >Kraft lignin from Pinus >lignin from bagasse. A mathematical model was developed to correlate the values of the diffusion constants with the structural characteristics of the lignins. The model was obtained by principal component regression, presenting an F test superior to the minimum required for the 95% confidence levei and a 0.89 correlation coefficient. The mathematical model showed that the higher the molecular mass and the content of total and aliphatic hydroxyls, the lower the diffusion constant and, consequently, the lower the 2,4-D release rate. In the case of the functional groups aromatic hydroxyls, methoxyls and carbonyls, the higher the content, the higher the release rate

ASSUNTO(S)

tecnologia de liberação controlada lignina

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