Sachês compósitos biodegradáveis à base de amido visando o acondicionamento de nutrientes para aplicação como fertilizantes

Abstract

The Brazilian agrarian system is responsible for a large part of the national GDP, even though agricultural production is dependent on foreign trade. In addition, many producers prioritize the use of NPK-type fertilizers for soil maintenance, neglecting other nutrients such as magnesium and manganese, which have synergy with phosphorus. Another problem is in the process of leaching of these nutrients, resulting in economic and environmental losses. In order to minimize this waste, the present work aims to produce biodegradable composite films for the release of nutrients P, Mg and Mn. In this way, nanoparticles of hydroxyapatite (HAP) and magnesium oxide (MgO) were synthesized by the precipitation method. For HAP, the obtaining speed was varied. For the synthesis of MgO, the temperature of the heat treatment used after its precipitation was varied. The HAP obtained by rapid synthesis showed solubilization similar to the slow one. The same behavior was observed for the MgO sample with heat treatment at 350 ° C for 2 h, in relation to the higher temperatures. For the production of starch-based thermoplastic composite films, different sources (potato, rice, cassava and corn) were processed in a mixing chamber coupled to a torque rheometer. After analyzing the solubility of the films in water, corn and potato films were selected for the production of starch and pectin blends. The biodegradation test showed higher rates of degradation in the blend composed of corn starch and in compositions with high levels of pectin, which also showed an increase in antimicrobial activity. For this reason, the blend of 75% corn starch and 25% pectin (m/m) was selected for incorporation of FAU zeolite modified with manganese, which varied from 1 to 5% (m/m) and did not result in changes in permeability to water vapor, but did in the mechanical properties. The presence of FAU caused the stress drop, however, it was responsible for the increase in deformation when 3% (m/m) of the particles were added. Sachets composed of 100 TPS, 75 TPS: 25 PEC and 75 TPS: 25 PEC: 3% FAU were produced for packaging the HAP and MgO nanoparticles. It is concluded that the films composed of starch and pectin helped in the process of making phosphorus and magnesium available. Composite films were effective for slow release of the ions of interest.