Li Wenli, Yu Jiahai, Zhang Shuyan, Tang Huan, Huang Tinglin
Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
Sci Total Environ. 2022 Dec 10;851(Pt 1):157954. doi: 10.1016/j.scitotenv.2022.157954. Epub 2022 Aug 11.
Given the possible ecological dangers of graphene oxide (GO), a thorough understanding of its aggregation behavior is essential. During industrial applications, GOs may be used as multi-layered, and there is some possibility that GOs are released into the water environment in the aggregated state. Thus, elucidating the fate of aggregated GO is valuable for evaluating their environmental fate. In this work, the effect of pH on the fate of aggregated graphene oxide (GO) was explored using experimental measurements and molecular dynamic simulations and promoted aggregation of GO upon the increase of pH was observed. Additional investigations show that the presence of oxidation debris (ODs) on GO served as the primary driver of the unanticipated trend in aggregation behavior. GO consists of lightly oxidized functionalized graphene sheets and highly oxidized ODs. Upon the increase of pH and the deprotonation of functional groups, ODs are stripped from GO due to electrostatic repulsions and steric hindrance of water molecules. The stripping of ODs decreased the zeta potential and increased the hydrophobicity of GO, thus accelerating the aggregation. Additionally, the stripped ODs may recombine to GO edges and bridged GOs, which also contribute to further aggregation. Functional group deprotonation, ODs stripping, OD bridging, double layer compression, and charge neutralization all worked together to promote aggregation, resulting in the formation of FG-water-OD aggregates. Overall, the presence of ODs complicates the structures and properties of GO and should be considered during the development of GO-related nanomaterials and the evaluation of their environmental impact.
鉴于氧化石墨烯（GO）可能存在的生态危害，深入了解其聚集行为至关重要。在工业应用中，GO可能以多层形式使用，并且存在GO以聚集状态释放到水环境中的可能性。因此，阐明聚集态GO的归宿对于评估它们的环境命运具有重要价值。在这项工作中，通过实验测量和分子动力学模拟研究了pH对聚集态氧化石墨烯（GO）归宿的影响，并观察到随着pH升高GO的聚集得到促进。进一步的研究表明，GO上氧化碎片（ODs）的存在是聚集行为中这一意外趋势的主要驱动因素。GO由轻度氧化的功能化石墨烯片和高度氧化的ODs组成。随着pH升高和官能团去质子化，由于水分子的静电排斥和空间位阻，ODs从GO上剥离。ODs的剥离降低了GO的zeta电位并增加了其疏水性，从而加速了聚集。此外，剥离的ODs可能会重新结合到GO边缘并桥接GO，这也有助于进一步聚集。官能团去质子化、ODs剥离、OD桥接、双层压缩和电荷中和共同作用促进聚集，导致形成FG-水-OD聚集体。总体而言，ODs的存在使GO的结构和性质变得复杂，在开发与GO相关的纳米材料及其环境影响评估过程中应予以考虑。
Zotero 插件