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Polarizable Molecular Simulations Reveal How Silicon-Containing Functional Groups Govern the Desalination Mechanism in Nanoporous Graphene
Journal of Chemical Theory and Computation ( IF 5.7 ) Pub Date : 2018-06-12 00:00:00 , DOI: 10.1021/acs.jctc.8b00226
Yudong Qiu 1 , Benedict R. Schwegler 2 , Lee-Ping Wang 1
Affiliation  

We report a molecular dynamics (MD) simulation study of reverse osmosis desalination using nanoporous monolayer graphene passivated by SiH2 and Si(OH)2 functional groups. A highly accurate and detailed polarizable molecular mechanics force field model was developed for simulating graphene nanopores of various sizes and geometries. The simulated water fluxes and ion rejection percentages are explained using detailed atomistic mechanisms derived from analysis of the simulation trajectories. Our main findings are as follows: (1) The Si(OH)2 pores possess superior ion rejection rates due to selective electrostatic repulsion of Cl ions, but Na+ ions are attracted to the pore and block water transfer. (2) By contrast, the SiH2 pores operate via a steric mechanism that excludes ions based on the size and flexibility of their hydration layers. (3) In the absence of ions, water flux is directly proportional to the solvent accessible area within the pore; however, simulated fluxes are lower than those inferred from recent experimental work. We also provide some hypotheses that could resolve the differences between simulation and experiment.

中文翻译:

可极化分子模拟揭示了含硅官能团如何控制纳米多孔石墨烯中的脱盐机理

我们报告了使用SiH 2和Si(OH)2官能团钝化的纳米多孔单层石墨烯进行反渗透脱盐的分子动力学(MD)模拟研究。开发了一种高度精确和详细的可极化分子力学力场模型,用于模拟各种尺寸和几何形状的石墨烯纳米孔。使用详细的原子机理解释了模拟的水通量和离子排斥百分比,这些机理是通过模拟轨迹的分析得出的。我们的主要结果如下:(1)中的Si(OH)2层的孔具有优异的离子排斥率由于氯的选择性静电排斥-离子,但钠+离子被吸引到毛孔并阻止水的转移。(2)相比之下,SiH 2孔隙是通过空间机理起作用的,该空间机理基于其水合层的大小和柔韧性而排除了离子。(3)在没有离子的情况下,水通量与孔内溶剂可及区域成正比;但是,模拟通量要比最近的实验工作所推断的要低。我们还提供了一些可以解决模拟与实验之间差异的假设。
更新日期:2018-06-12
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