Abstract

As the largest aromatic polymer of natural origin, lignin arouses the interest of researchers and industries worldwide. Its three-dimensional polymeric aromatic structure, besides being complex, varies depending on its botanical origin and extraction process, which makes its use as a raw material difficult. Currently, the main destination for lignin is burning for energy production. This study presents the characterization of lignin and lignin microparticles after processing by ultrasonic irradiation. Analyzes were performed to verify the dimensional, morphological and antioxidant characteristics of the particles as well as changes in their structure after sonication. A sample of eucalyptus wood lignin isolated from kraft black liquor was used and the modifications were analyzed by X-ray diffraction analysis, zeta potential, FTIR spectroscopy, particle size, scanning electron microscopy, TGA thermogravimetric analysis, phenolic compounds total by Folin–Ciocalteau and antioxidant analysis by DPPH. The results demonstrate that there was no change in the chemical structure of lignin with the application of ultrasonic radiation, but the reduction in particle size was able to reduce zeta potential with a lower probability of agglomeration between them, and consequent greater stabilization in solution. Also, the ultrasound treatment was able to increase the thermal stability of the lignin microparticle with a decrease of the mass loss rate with the time. The reduction in particle size was also able to expose a larger number of phenolic compounds and thereby increase the total phenolic content and lignin antioxidant activity making the lignin microparticle a promising material to study and application on food-active biodegradable polymers.

中文翻译：

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用于可生物降解的聚合物的物理和抗氧化增强的木质素微粒的开发和表征

摘要

木质素作为天然来源的最大芳香族聚合物，引起了全世界研究人员和行业的兴趣。它的三维聚合芳族结构，除了复杂之外，还取决于其植物来源和提取工艺，因此很难用作原料。目前，木质素的主要目的地是燃烧以生产能源。这项研究提出了木质素和木质素微粒经过超声辐射处理后的表征。进行分析以验证颗粒的尺寸，形态和抗氧化特性以及超声处理后其结构的变化。使用了从牛皮纸黑液中分离出的桉木木质素样品，并通过X射线衍射分析，ζ电位，FTIR光谱，粒度，扫描电子显微镜，TGA热重分析，Folin–Ciocalteau的总酚类化合物和DPPH的抗氧化剂分析。结果表明，使用超声波辐射，木质素的化学结构没有变化，但是粒径的减小能够降低zeta电位，使它们之间的团聚可能性降低，因此溶液的稳定性更高。而且，超声处理能够增加木质素微粒的热稳定性，同时质量损失率随时间降低。