The widespread applications of carbon quantum dots (CQDs) have attracted much attention. This study presents a novel research system to study the transport and retention of CQDs in homogeneous and heterogeneous porous media. The light transmission visualization technique was used to visualize the real-time distribution and transport of CQDs. Results showed that the increase in quartz sand particle size and increased pH significantly enhanced the transport of CQDs. Due to the negative surface charge of CQDs shielded by high IS, the agglomeration of CQDs enhanced the clogging of CQDs. Particularly, significant aggregated fluorescence quenching of CQDs occurred at IS = 100 mM and IS = 200 mM. In heterogeneous media, the layer structure alteration and preferential flow contribute significantly in the transport of CQDs. Compared to the fine sand layer, most of the CQDs outflow from the coarse sand layer. The breakthrough curves for CQD transport in porous media can be matched by a simplified double-Monod model with high accuracy (R² > 0.92). Moreover, the DLVO theory and clogging mechanism well explain the environmental behavior of CQDs in 2D porous media. This study visualized the fate of CQDs in 2D porous media, enabling us to further assess and predict their environmental risks.

中文翻译：

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均质和非均相多孔介质中碳量子点传输的实时可视化


碳量子点 （CQD） 的广泛应用引起了广泛关注。本研究提出了一种新的研究系统来研究 CQDs 在均质和非均质多孔介质中的传输和保留。结果表明，石英砂粒径的增加和 pH 值的增加显著增强了 CQDs 的传输。由于 CQDs 的表面负电荷被高 IS 屏蔽，CQDs 的团聚增强了 CQD 的堵塞。 CQDs 的显著聚集荧光猝灭发生在 IS = 100 mM 和 IS = 200 mM 时。在非均质介质中，层结构改变和优先流对 CQDs 的输运有显著贡献。与细砂层相比，大部分 CQDs 从粗砂层流出。多孔介质中 CQD 传输的突破曲线可以通过高精度的简化双 Monod 模型 （R² > 0.92） 进行匹配。此外，DLVO 理论和堵塞机制很好地解释了 CQD 在二维多孔介质中的环境行为。这项研究可视化了 CQD 在 2D 多孔介质中的命运，使我们能够进一步评估和预测其环境风险。