de Carvalho Arjona Jessica, das Graças Silva-Valenzuela Maria, Wang Shu-Hui, Valenzuela-Diaz Francisco Rolando
Department of Metallurgical and Materials Engineering, Polytechnic School, University of Sao Paulo. Av. Prof. Mello Moraes 2463, Sao Paulo 05508-030, Brazil.
Polymers (Basel). 2021 Feb 26;13(5):722. doi: 10.3390/polym13050722.
Urea is the most used fertilizer around the world as the main source of nitrogen to soil and plants. However, the administration of nitrogen dosage is critical, as its excess can be harmful to the environment. Therefore, the encapsulation of urea to achieve control on its release rates has been considered in several areas. In this work, encapsulation of urea by biodegradable polymer poly(3-hydroxybutyrate) (PHB) and its nanocomposites, namely PHB/MMT and PHB/OMMT, producing microcapsules by emulsion method is carried out. MMT and OMMT refer to Brazilian clays in a natural state and organophilized, respectively. In addition, the microcapsules are thus prepared to have their physicochemical characteristics investigated, then tested for biodegradation. Increment of microcapsules' crystallinity due to the increased amount of poly(vinylacetate) (PVA), as emulsifier agent in the continuous phase, was confirmed by X-ray diffractometry (XRD) and atomic force microscopy (AFM). The presence of urea within microcapsules was verified by XRD, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The soil biodegradation assessments showed that PHB/OMMT microcapsules present higher degradation rates in sandy soils. The overall results suggest that the composites performed better than neat PHB and are very promising; moreover, PHB/OMMT microcapsules proved to be the best candidate for the controlled-release of urea in soils.
尿素是全球使用最广泛的肥料，是土壤和植物氮素的主要来源。然而，氮肥用量的控制至关重要，因为过量使用会对环境有害。因此，在多个领域都考虑对尿素进行包封以控制其释放速率。在本研究中，采用乳液法通过可生物降解聚合物聚（3-羟基丁酸酯）（PHB）及其纳米复合材料（即PHB/蒙脱土（MMT）和PHB/有机蒙脱土（OMMT））对尿素进行包封，制备微胶囊。MMT和OMMT分别指天然状态和有机化的巴西黏土。此外，制备微胶囊并对其理化特性进行研究，然后进行生物降解测试。通过X射线衍射仪（XRD）和原子力显微镜（AFM）证实，由于连续相中乳化剂聚醋酸乙烯酯（PVA）用量增加，微胶囊的结晶度提高。通过XRD、热重分析（TGA）和扫描电子显微镜（SEM）验证了微胶囊中尿素的存在。土壤生物降解评估表明，PHB/OMMT微胶囊在砂质土壤中具有更高的降解速率。总体结果表明，复合材料的性能优于纯PHB，非常有前景；此外，PHB/OMMT微胶囊被证明是土壤中尿素控释的最佳候选材料。
