Transport of saltwater through pristine and positively charged single-layer graphene nanoporous membranes is investigated using molecular dynamics simulations. Pressure-driven flows are induced by motion of specular reflecting boundaries at feed and permeate sides with constant speed. Unlike previous studies in the literature, this method induces a desired flow rate and calculates the resulting pressure difference in the reservoirs. Due to the hexagonal structure of graphene, the hydraulic diameters of nano-pores are used to correlate flow rate and pressure drop data. Simulations are performed for three different pore sizes and flow rates for the pristine and charged membrane cases. In order to create better statistical averages for salt rejection rates, ten different initial conditions of Na⁺ and Cl⁻ distribution in the feed side are used for each simulation case. Using data from 180 distinct simulation cases and utilizing the Buckingham Pi theorem, we develop a functional relationship between the volumetric flow rate, pressure drop, pore diameter, and the dynamic viscosity of saltwater. A linear relationship between the volumetric flow rate and pressure drop is observed. For the same flow rate and pore size, charged membranes exhibit larger pressure drops. Graphene membranes with 9.90 Å pore diameter results in 100% salt rejection with 163.2 l/h cm² water flux, requiring a pressure drop of 35.02 MPa.

中文翻译：

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盐水通过原始膜和带正电的石墨烯膜传输

使用分子动力学模拟研究了盐水通过原始的和带正电的单层石墨烯纳米多孔膜的传输。压力驱动的流量是由进料侧和渗透侧的镜面反射边界以恒定速度运动引起的。与文献中先前的研究不同，此方法可产生所需的流量并计算储层中的压力差。由于石墨烯的六边形结构，纳米孔的水力直径用于关联流量和压降数据。针对原始和带电膜的情况，针对三种不同的孔径和流速进行了模拟。为了创建更好的盐去除率统计平均值，需要选择十种不同的Na ⁺初始条件和Cl ^-中的进料侧分配用于每个模拟情况。利用来自180个不同模拟案例的数据并利用白金汉Pi定理，我们建立了体积流量，压降，孔径和盐水动态粘度之间的函数关系。观察到体积流量和压降之间的线性关系。对于相同的流速和孔径，带电的膜表现出较大的压降。孔径为9.90Å的石墨烯膜可通过163.2 l / h cm ^2的水通量实现100％的脱盐率，要求压降为35.02 MPa。