Chemistry Department , The University of California, Davis , Davis , California 95616 , United States.
Department of Civil and Environmental Engineering , Stanford University , Stanford , California 94305 , United States.
J Chem Theory Comput. 2018 Aug 14;14(8):4279-4290. doi: 10.1021/acs.jctc.8b00226. Epub 2018 Jul 9.
We report a molecular dynamics (MD) simulation study of reverse osmosis desalination using nanoporous monolayer graphene passivated by SiH and Si(OH) 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) 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 SiH 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.
我们报告了使用 SiH 和 Si(OH)官能团钝化的单原子层石墨烯的反渗透脱盐的分子动力学（MD）模拟研究。为了模拟各种尺寸和形状的石墨烯纳米孔，开发了一个高度准确和详细的极化分子力学力场模型。通过分析模拟轨迹得出的详细原子机制来解释模拟的水通量和离子截留率。我们的主要发现如下：（1）由于 Cl 离子的静电排斥，Si(OH) 孔具有优越的离子截留率，但 Na 离子被吸引到孔中并阻止水的传递。（2）相比之下，SiH 孔通过空间位阻机制来排除离子，这取决于它们水合层的大小和灵活性。（3）在没有离子的情况下，水通量与孔内可及溶剂面积成正比；然而，模拟通量低于最近实验工作推断的值。我们还提供了一些假设，可以解决模拟与实验之间的差异。
