Desenvolvimento de sachês biodegradáveis à base de amido para liberação do micronutriente zinco

Abstract

Due to the great importance of agriculture in human activities and the economy, studies have been directed in order to increase the efficiency of agricultural production. This project aimed to increase zinc oxide (ZnO) solubility by decreasing the size of the particles and further place them in starch sachets to work as a release system. To obtain nanoparticles, top-down and bottom-up approaches were evaluated using high energy grinding (HEG) and synthetic methods. The results obtained after grinding showed that the process carried out for 16 h allowed the obtaining of nanoparticles with an average diameter of 71 ± 41 nm, with smaller size and greater homogeneity, compared to the commercial one (174 ± 95 nm). Regarding solubility, the ground nanoparticles proved to be more efficient than the synthesized and commercial ones, since they promoted the release of 81 ± 4% of Zn2+ ions in 24 h. The TPS processing was carried out in an intensive mixer in an internal chamber and, subsequently, thermo-pressed. For developing the sachets, a corn starch matrix was used, because of this material biodegradability. Due to hydrophilicity and low mechanical resistance of starch, montmorillonite clay (MMT) was evaluated as reinforcement. The starch sachet with 1% MMT increased the barrier property by 24% and also improved the mechanical features, increasing the tensile and elongation resistance by 52% and 57%, respectively. The 24 h release essay of ZnO from both TPS (82 ±12%) and TPS reinforced with 1% MMT sachets (66 ± 11%) showed similar behavior to the free ZnO profile. Therefore, it was possible to obtain a starch sachet capable of ZnO fertilizer packaging, enabling to minimize losses through aerial dispersion.