物理化学学报 >> 2015, Vol. 31 >> Issue (6): 1025-1034.doi: 10.3866/PKU.WHXB201504141

理论与计算化学 上一篇    下一篇

反渗透过程中双壁碳纳米管通水阻盐性能的分子动力学模拟

谌庄琳, 贺高红, 张宁, 郝策   

  1. 大连理工大学石油与化学工程学院, 辽宁盘锦124221
  • 收稿日期:2014-12-11 修回日期:2015-04-13 发布日期:2015-06-05
  • 通讯作者: 张宁 E-mail:zhangning@dlut.edu.cn
  • 基金资助:

    国家杰出青年科学基金项目(21125628), 中央高校基本科研业务费专项资金(DUT14RC(3)077)和盘锦市精细化工国家重点实验室建设经费(JH2014009)资助

Molecular Dynamics Simulation of Reverse-Osmotic Salt Rejection and Water Transport through Double-Walled Carbon Nanotube

SHEN Zhuang-Lin, HE Gao-Hong, ZHANG Ning, HAO Ce   

  1. School of Petroleum and Chemical Engineering, Dalian University of Technology, Panjin 124221, Liaoning Province, P. R. China
  • Received:2014-12-11 Revised:2015-04-13 Published:2015-06-05
  • Contact: ZHANG Ning E-mail:zhangning@dlut.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation for Distinguished Young Scholars of China (21125628), Fundamental Research Funds for the Central Universities, China (DUT14RC(3)077) and State Key Laboratory of Fine Chemicals (Panjin) Project, China (JH2014009).

摘要:

采用分子动力学模拟方法, 探究了非常规双壁碳纳米管(DWCNT)在反渗透过程中, 不同内外管间距对管道内水分子与盐离子运动行为的影响. 本文采用0.5 mol·L-1氯化钠水溶液模拟海水, 内管始终采用CNT(8,8)型, 并对盐水层施加恒力模拟反渗透压. 重点考察盐离子数量分布与通水情况, 计算水分子平均力势, 并分析水分子氢键寿命与偶极矩分布. 结果表明, 管间距不仅影响上述各项性质, 还会改变盐离子与水分子在碳管中的渗透特性. 模拟结果显示, 小尺寸DWCNT可以有效实现盐水分离但水通量较小, 大尺寸DWCNT的水容量较大但阻盐效率不高, 而中尺寸DWCNT (即: 管间距为0.815 nm)则具有最佳的通水阻盐性能. 本文试图从分子层面揭示了DWCNT通水阻盐机理, 并为人们设计新型海水淡化渗透膜提供理论指导.

关键词: 双壁碳纳米管, 分子动力学模拟, 管间距, 反渗透, 海水淡化

Abstract:

Molecular dynamics simulation was used to study the effect of the outer-wall on water flux in the inner channel by varying the inter-layer spacing of unconventional double-walled carbon nanotube (DWCNT) under reverse-osmosis conditions. Salt rejection and the water transport behavior inside the DWCNT were also examined. In the simulation, 0.5 mol·L-1 NaCl aqueous solution was used to mimic seawater, and the chiral index of the inner-wall was fixed at (8, 8). A constant force on the salt solution produced pressure. Calculation of the number density profile of ions along the DWCNT axis showed that the water could be separated completely from the NaCl aqueous solution in some types of DWCNTs studied. Analyses of the hydrogen-bond lifetime, potential of mean force, and dipole moment distribution of the water molecules inside the DWCNT showed different permeabilities by water molecules and ions. An increase in the inter-layer spacing improved water flow in the DWCNT, which decreased the salt rejection performance. Finally, it was found that DWCNT with an inter-layer spacing of 0.815 nm gave the optimum balance between water flux and salt rejection. This study provides a molecular insight into the use of DWCNT in desalination, and will enable the design of improved reverse-osmosis membranes with high performance in terms of salt rejection and water permeability.

Key words: Double-walled carbon nanotube, Molecular dynamics simulation, Inter-layer spacing, Reverse osmosis, Desalination

MSC2000: 

  • O649