CONTROLLED-RELEASE OF IMIDACLOPRID FROM A LIGNIN MATRIX - WATER RELEASE KINETICS AND SOIL MOBILITY STUDY

Formulations of the insecticide imidacloprid were made using a commerc ially available pine kraft lignin. The release kinetics of imidaclopri d from granules with variation in the loadings of the insecticide and granule sizes were evaluated in water under dynamic flow conditions. T he release data were fitted to the generalized model M-t/M-z = kt(n) c, where M-t/M-z is the percentage of insecticide released at time t, k and c are constants, and n is another constant that indicates the m echanism of release. The results indicated that the release of imidacl oprid was diffusion-controlled. The time taken for 50% of the active i ngredient to be released into water, T-50, was also calculated for the comparison of formulations. The results showed that the formulation w ith the higher loading of imidacloprid had the higher value of T-50, w hich means a slower release of the active ingredient. In a related exp eriment, it was found that as the size of this formulation decreased, the release of the active ingredient was faster. In addition, mobiliti es of technical and formulated imidacloprid were compared by using soi l columns simulating a layered bed system commonly used under a plasti c greenhouse. The use of formulated imidacloprid produced a less verti cal distribution of the active ingredient compared to the technical pr oduct. Sorption capacities of the various soil constituents for imidac loprid molecules were also calculated by using batch experiments. The results obtained were in agreement with those for sorption in dynamic conditions.