In silico study of structure and water dynamics in CNT/polyamide nanocomposite reverse osmosis membranes
In silico study of structure and water dynamics in CNT/polyamide nanocomposite reverse osmosis membranes
复制标题
CNT/聚酰胺纳米复合反渗透膜结构和水动力学的计算机研究
DOI：
10.1039/d0cp03864d
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发表时间：
2020
影响因子：
3.3
通讯作者：
Xiao Guyu
中科院分区：
文献类型：
--
作者：
Gu Qi-an;Li Ke;Li Shanlong;Cui Rui;Liu Lifen;Yu Chunyang;Wang Yuling;Zhou Yongfeng;Xiao Guyu
碳纳米管基反渗透膜一直被认为是最有前途的海水淡化技术之一。然而，遗憾的是，对于碳纳米管在这些纳米复合膜中的确切作用还没有完全的了解。为了解决这一问题，本研究分别构建了PA（纯聚酰胺膜）、PA - cnt1（嵌入垂直于膜表面的碳纳米管的聚酰胺纳米复合膜）和PA - cnt2（嵌入平行于膜表面的碳纳米管的聚酰胺纳米复合膜）三个原子模型。然后，通过平衡分子动力学（EMD）和非平衡分子动力学（NEMD）模拟研究了这三种模型的结构和水动力学。EMD模拟显示，由于碳纳米管的加入，PA矩阵的堆叠更好，而且这种影响在PA - cnt1中比在PA - cnt2中更为显著。同时，发现碳纳米管口附近的PA基质作为阻碍碳纳米管内外水分子交换的障碍物。在NEMD模拟中，我们发现水分子被引导远离碳纳米管，因为周围的PA矩阵堆叠得更好。部分覆盖的碳纳米管可能无助于增加PA-CNT1中的水通量，而被引导的水分子和受碳纳米管影响的较小的聚合物区域有助于增加PA-CNT2中的相对较高的通量。目前的工作可能有助于全面了解碳纳米管在反渗透过程中的作用。
CNT-based reverse osmosis membranes have long been regarded as one of the most promising candidates for water desalination. However, it is a pity that there is no complete understanding of the exact role of CNTs in those nanocomposite membranes. To address this issue, three atomistic models of PA (pure polyamide membrane), PA–CNT1 (polyamide nanocomposite membrane with an embedded carbon nanotube oriented vertical to the membrane surface) and PA–CNT2 (polyamide nanocomposite with an embedded carbon nanotube oriented parallel to the membrane surface) were constructed respectively in this work. Then, equilibrium molecular dynamics (EMD) and non-equilibrium molecular dynamics (NEMD) simulations were conducted to investigate the structure and water dynamics in these three models. The EMD simulations revealed a better stacking of the PA matrix due to the addition of the CNT and this impact was more significant in PA–CNT1 than in PA–CNT2. Meanwhile, PA matrix near the mouth of the CNT was found to behave as an obstruction that hindered the exchange of water molecules inside and outside the CNT. In NEMD simulations, we found that water molecules were guided away from the CNT because of the better stacked surrounding PA matrix. The partially covered CNT might not help to increase water flux in PA–CNT1 while guided water molecules and the smaller polymer region afftected by the CNT contributed to a relatively high flux in PA–CNT2. The current work might serve as a comprehensive understanding of the role of CNTs in the reverse osmosis process.