Graphene is a material with high potential in the development of advanced applications, such as 3D printing. In the current scenario, it is obvious that technological progress should align with sustainability, therefore, it is necessary to search for efficient and sustainable alternatives to the liquid phase exfoliation of graphene. In this work, chestnut tannins were employed as surfactants for graphene exfoliation in aqueous media, via ultrasound exfoliation and high-shear exfoliation. The effect of the initial concentration of graphite, the initial concentration of tannin and the exfoliation time over the concentration of the obtained graphene suspensions and mass yield was assessed, showing that comparable values to NMP based exfoliation were obtained. Obtained graphene flakes were morphologically characterized by Raman spectroscopy and Transmission Electron Microscopy, and results showed that high-shear exfoliation resulted in graphene flakes with the highest I/I ratio and more homogenous thickness. Life Cycle Assessment of the exfoliation processes revealed the environmental benefits of water-based exfoliation processes compared to traditional process based on NMP solvent. A sensitivity analysis showed that environmental impacts could be reduced if renewable energy sources are considered. High-shear exfoliation with initial concentration of graphite of 5 mg·mL, tannin concentration of 1 mg·mL and shearing time of 15 min emerged as the most balanced choice between quality and sustainability.

中文翻译：

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用于石墨烯可持续生产的水基和单宁辅助液相剥离

石墨烯是一种在开发3D打印等先进应用方面具有巨大潜力的材料。在当前情况下，技术进步显然应与可持续性相一致，因此，有必要寻找高效且可持续的石墨烯液相剥离替代方案。在这项工作中，栗子单宁被用作表面活性剂，通过超声波剥离和高剪切剥离，在水介质中进行石墨烯剥离。评估了石墨的初始浓度、单宁的初始浓度和剥离时间对所获得的石墨烯悬浮液的浓度和质量产率的影响，表明获得了与基于NMP的剥离相当的值。通过拉曼光谱和透射电子显微镜对所得石墨烯薄片进行形态表征，结果表明，高剪切剥离导致石墨烯薄片具有最高的 I/I 比和更均匀的厚度。剥离工艺的生命周期评估揭示了与基于 NMP 溶剂的传统工艺相比，水基剥离工艺的环境效益。敏感性分析表明，如果考虑使用可再生能源，可以减少对环境的影响。石墨初始浓度为 5 mg·mL、单宁浓度为 1 mg·mL、剪切时间为 15 分钟的高剪切剥离成为质量和可持续性之间最平衡的选择。