Exploration & Development Research Institute of Shengli Oilfield Co. Ltd, SINOPEC , Dongying 257015 , Shandong , China.
Technical Institute of Physics and Chemistry , Chinese Academy of Sciences , Beijing 100190 , China.
ACS Appl Mater Interfaces. 2018 Oct 31;10(43):37014-37022. doi: 10.1021/acsami.8b12871. Epub 2018 Oct 18.
Selective transport of liquids is an important process in the energy and environment industry. The increased energy consumption and the demands of clean water and fossil fuels have urged the development of high-performance membrane technologies. Nanoscale channels with the critical size for molecular sieving and atomistically smooth walls for significant boundary slippage are highly promising to balance the tradeoff between permeability and selectivity. In this work, we explore the molecular structures and dynamics of organic solvents and water, which are confined within nanoscale two-dimensional galleries between graphene or graphene oxide sheets. Molecular dynamics simulation results show that the layered order and significant interfacial slippage are universal for all molecular liquids, leading to notable flow enhancement for channels with a width of few nanometers, in the order of ethylene glycol > butanol > ethanol > hexane > toluene > water > acetone. The extracted dependence of permeability, selectivity on the channel width, and properties of molecular liquids clarify the underlying mechanisms of selective mass transport in nanofluidics, which help to understand and control the filtration and separation processes of molecular liquids. The performance of graphene oxide membranes for permeation and filtration is finally discussed based on the calculated flow resistance for pressure-driven flow or molecular diffusivity for diffusive flow, as well as the solubility and wettability of membranes.
液体的选择性传输是能源和环境工业中的一个重要过程。能源消耗的增加以及对清洁水和化石燃料的需求，促使人们开发高性能的膜技术。具有分子筛分临界尺寸的纳米通道和原子级光滑的壁面，有利于显著的边界滑移，这在渗透性和选择性之间的权衡中具有很大的优势。在这项工作中，我们探索了受限在石墨烯或氧化石墨烯片之间的纳米二维通道内的有机溶剂和水的分子结构和动力学。分子动力学模拟结果表明，所有分子液体都具有层状有序和显著的界面滑移，对于宽度为几个纳米的通道，会显著增强流动，其增强顺序为：乙二醇>正丁醇>乙醇>己烷>甲苯>水>丙酮。渗透率、选择性对通道宽度的依赖性以及分子液体的性质，阐明了纳米流体中选择性质量传输的基本机制，有助于理解和控制分子液体的过滤和分离过程。最后，根据压力驱动流动的计算流动阻力或扩散流动的分子扩散率，以及膜的溶解度和润湿性，讨论了氧化石墨烯膜的渗透和过滤性能。
