Glutaraldehyde crosslinked sodium alginate beads containing liquid pesticide for soil application

This paper presents experimental results on the successful encapsulation of a natural liquid pesticide 'neem (Azadirachta Indica A. Juss.) seed oil' hereafter designated as NSO, using sodium alginate (Na-Alg) as a controlled release (CR) polymer after crosslinking with glutaraldehyde (GA). The NSO-containing beads have been prepared by changing the experimental variables such as the extent of crosslinking and the amount of loading in order to optimize the process variables. The absence of chemical interactions between active ingredients and polymer as well as crosslinking agent was confirmed by FTIR spectral measurements. The SEM data indicated that the structure of the walls of the beads are smooth and nonporous. The swelling results indicated that swelling of the polymeric beads decreases with increasing exposure time to the crosslinking agent. However, no significant variation in swelling was observed with different amounts of NSO loading. In order to understand the crosslinkability and its effect on the NSO release patterns of the beads, an attempt was made to calculate the molar mass between crosslinks using the Flory-Rehner equation. The release data have been fitted to an empirical equation to estimate the kinetic parameters. (C) 2000 Elsevier Science BSI. All rights reserved.