Controlled Release Formulations of 2,4-Dichlorophenoxyacetic Acid with Ecofriendly Matrices for Agricultural and Environmental Sustainability

Controlled release formulations (CRFs) of 2,4-dichlorophenoxyacetic acid (2,4-D) with chitosan (CTS) and chitosan-starch (CTS-STA) matrices were prepared in their un-crosslinked and crosslinked forms. Pesticide-matrix interactions were probed by FT-IR, while TGA and SEM provided information on the morphological characteristics of the pesticide-loaded beads. The CRF beads are more hydrophilic at pH 4 than at pH 8 due to increased number and strength of hydrogen bonds at pH 4. Crosslinking reduces the water uptake and expansion capacity of the beads in both acidic and basic media. Swelling of both bead types in water obeys first-order kinetics. Release of 2,4-D from the beads is of the burst type which exhibits zero-order kinetics. Measured n values range from 0.32 to 0.90, indicative of a non-Fickian diffusional release mechanism controlled by both water diffusion into, and relaxation of, the beads. These characteristics predispose the matrix blends as suitable biomaterials for agricultural and environmental sustainability.