Transport of hydrated nitrate and nitrite ions through graphene nanopores in aqueous medium,Journal of Computational Chemistry

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Transport of hydrated nitrate and nitrite ions through graphene nanopores in aqueous medium
Journal of Computational Chemistry ( IF 3.4 ) Pub Date : 2020-06-05 , DOI: 10.1002/jcc.26356
Sushma Yadav _{1,

2} , Amalendu Chandra ₁

Affiliation

Nitrate ( NO3− ) and nitrite ( NO2− ) ions are naturally occurring inorganic ions that are part of the nitrogen cycle. High doses of these ions in drinking water impose a potential risk to public health. In this work, molecular dynamics simulations are carried out to study the passage of nitrate and nitrite ions from water through graphene nanosheets (GNS) with hydrogen‐functionalized narrow pores in presence of an external electric field. The passage of ions through the pores is investigated through calculations of ion flux, and the results are analyzed through calculations of various structural and thermodynamic properties such as the density of ions and water, ion–water radial distribution functions, two‐dimensional density distribution functions, and the potentials of mean force of the ions. Current simulations show that the nitrite ions can pass more in numbers than the nitrate ions in a given time through GNS hydrogen‐functionalized pore of different geometry. It is found that the nitrite ions can permeate faster than the nitrate ions despite the former having higher hydration energy in the bulk. This can be explained in terms of the competition between the number density of the ions along the pore axis and the free energy barrier calculated from the potential of mean force. Also, an externally applied electric field is found to be important for faster permeation of the nitrite over the nitrate ions. The current study suggests that graphene nanosheets with carefully created pores can be effective in achieving selective passage of ions from aqueous solutions.

中文翻译：

水合硝酸根和亚硝酸根离子通过石墨烯纳米孔在水性介质中的传输

硝酸根 (NO3-) 和亚硝酸根 (NO2-) 离子是天然存在的无机离子，它们是氮循环的一部分。饮用水中高剂量的这些离子对公共健康构成潜在风险。在这项工作中，进行了分子动力学模拟，以研究在外部电场存在的情况下，硝酸根和亚硝酸根离子从水中通过具有氢官能化窄孔的石墨烯纳米片 (GNS) 的过程。通过计算离子通量来研究离子通过孔的通道，并通过计算各种结构和热力学特性（例如离子和水的密度、离子-水径向分布函数、二维密度分布函数）来分析结果，以及离子的平均力势。目前的模拟表明，在给定的时间内，亚硝酸根离子可以通过不同几何形状的 GNS 氢官能化孔的数量多于硝酸根离子。发现亚硝酸根离子可以比硝酸根离子更快地渗透，尽管前者在本体中具有更高的水合能。这可以通过沿孔轴的离子数密度与根据平均力势计算的自由能垒之间的竞争来解释。此外，发现外部施加的电场对于亚硝酸盐在硝酸根离子上的更快渗透很重要。目前的研究表明，具有精心制造的孔的石墨烯纳米片可以有效地实现离子从水溶液中的选择性通过。

更新日期：2020-06-05

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