CONTROLLED-RELEASE OF 2,4-D FROM GRANULE MATRIX FORMULATIONS BASED ON6 LIGNINS

Six lignins were used to obtain granular controlled release matrix for mulations of the herbicide 2,4-D (2,4-dichlorophenoxyacetic acid). The water insoluble lignins were sourced from sugar cane (Saccharum offic inarum) bagasse and Eucalyptus sp. and Pinus sp. woods. Each lignin wa s characterized by its functional groups and molecular weight distribu tions. The formulations were prepared by melting the 2,4-D and mixing in the lignins individually and then granulating (to 0.7-1.0 mm) the g lassy matrix. Release rates determined in static water were correlated to a diffusion-controlled mechanism according to the square root of t ime. Principal component regression of the slopes of these lines showe d that these depend inversely on the molecular weight and the total an d aliphatic hydroxyls of the lignins. For the other functional groups (aromatic hydroxyls, methoxyls, and carbonyls), the higher their conte nts, the higher the diffusion and release rates.