Microencapsulação de KNO₃ com amido de milho nativo e modificado por atomização

Abstract

The continuous growth of the global population has demanded increased food production, leading to the excessive use of fertilizers and worsening environmental damage. A promising way to mitigate these impacts is the use of enhanced efficiency fertilizers (EEFs), which consist of nutrients encapsulated in polymeric, ceramic, or composite matrices that control the release of nutrients into the soil. In this study, corn starch (modified or not) was evaluated as a matrix for encapsulating nutrients (K and N in the form of KNO₃) using the spray drying technique. The variation in the equimolar ratio of the encapsulated salts was analyzed, and in the case of amphoteric starch (with both positive and negative charges), its net charge and the degree of substitution of the cationic (3-chloro-2-hydroxypropyltrimethylammonium chloride) and anionic (phosphate) functional groups were determined. Before spray drying, citric acid was directly added to the starch/KNO₃ solution, allowing for the formation of microcapsules with and without crosslinking. This approach aimed to promote in situ crosslinking of the biopolymers, with the goal of delaying nutrient release and enhancing the structural resistance of the microcapsules. Additionally, swelling tests were conducted to assess the effects of crosslinking on the physicochemical properties of the materials. The results indicated that crosslinked corn starch showed greater resistance to solubility and better control of nutrient release, proving more effective in simulated agricultural applications. In contrast, amphoteric starch was less efficient due to its high solubility in water, which compromised its controlled release capacity. Besides, the study proposes a pedagogical approach for high school education, based on the theme “The Chemistry of Fertilizers: Environmental Impacts and Polymer-Based Solutions,” using the STS (Science, Technology, and Society) perspective as a didactic resource.