Synthesis and Characterization of Chitosan-PVA hydrogels for pesticide release

Chitosan (Ch)-Polyvinyl (alcohol) (PVA) hydrogels cross-linked with sodium tripolyphosphate were synthetized to obtain a polymer matrix encapsulating an insecticide (active ingredient: imidacloprid). Imidacloprid release tests were performed separately with moist and lyophilized hydrogel beads with a diameter of 3.47 and 3.30 mm respectively. The concentration of the insecticide released in the medium was determined by UV-Visible spectroscopy, reaching equilibrium for wet hydrogels at 72h at a concentration of 330 mg L−1 and 281 mg L−1 in 48h for lyophilized hydrogels, comparing it with a maximum load of 330.18 mg L−1of imidacloprid contained in the hydrogels. The characterization of hydrogels was performed by Fourier transform infrarred spectroscopy (FTIR) to determine the functional groups. The morphology of the polymer matrix of the hydrogels was carried out in a scanning electron microscope (SEM). The size distribution and diameter of bead samples were observed through a stereomicroscope. The percentage of humidity of the hydrogels was determined obtaining 94.8% once the imidacloprid was released. the pore size of the samples was determined by the Brunauer-Emmet-Teller (BET) technique. The techniques used indicated that controlled release of imidacloprid could be more efficient with wet hydrogels in relation to the maximum load of imidacloprid contained, for protection of crops is necessary for a long time because of insecticide disponible in the soil.