Non-equilibrium molecular dynamics simulations were employed to explore the Mg²⁺/Li⁺ separation efficiency of pristine and functionalized carbon nanotubes (CNT) for the MgCl₂/LiCl solution. It is initially found that the dehydration degree of the first shell of Li⁺ near the mouth of pristine CNT membrane is greater than that of Mg²⁺, so the energy barrier for Mg²⁺ entering CNT membrane is generally smaller than the counterpart of Li⁺, emphasizing the potential of CNTs for the separation of Mg²⁺/Li⁺. Further, Mg²⁺ experiences greater attraction from the CNT membrane coated with carboxyl groups relative to Li⁺, which further enhances the permeability of Mg²⁺ over Li⁺. Therefore, the carboxyl-CNT membrane demonstrates enhanced Mg²⁺/Li⁺ selectivity compared to the pristine CNT membranes. Nevertheless, for the CNT membrane grafting with amino groups, the Mg²⁺ undergoes enhanced repulsion from the CNT mouth relative to Li⁺, so the retention time of Mg²⁺ at the fluid-CNT interface is increased, which makes the amino-CNT membrane to preferentially passing through Li⁺. Consequently, the Mg²⁺/Li⁺ selectivity is reduced in amino-CNT membrane, with respect to the pristine CNT membrane. It is also found that while the selectivity of Mg²⁺/Li⁺ increases with the external driving force for the pristine and carboxyl-CNT membranes, the amino-CNT membrane undergoes an opposite trend with the driving force. We note that in all the cases considered, the CNT membranes mounted with carboxyl groups deliver the best Mg²⁺/Li⁺ separation efficiency for carrying negative charges at the pore mouth. Our findings could facilitate the development in membrane design for efficient Mg²⁺/Li⁺ separation.

非平衡分子动力学模拟用于探索原始和功能化碳纳米管 (CNT) 对 MgCl ₂ /LiCl 溶液的 Mg ²⁺ /Li ^{+分离效率。}初步发现，靠近原始CNT膜口的Li ⁺第一壳层的脱水程度大于Mg ²⁺，因此Mg ²⁺进入CNT膜的能垒普遍小于Li对应的能垒。 ⁺，强调了碳纳米管在分离 Mg ²⁺ /Li ⁺方面的潜力。此外，Mg ^{2+相对于Li +} ，涂有羧基的CNT膜受到更大的吸引力，这进一步增强了Mg ²⁺相对于Li ⁺的渗透性。因此，与原始CNT膜相比，羧基-CNT膜表现出增强的Mg ²⁺ /Li ^{+选择性。}然而，对于接枝氨基的 CNT 膜，Mg ^{2+从 CNT 口相对于 Li +}的排斥力增强，因此 Mg ²⁺在流体-CNT 界面的停留时间增加，这使得氨基-CNT膜优先通过Li ⁺。因此，Mg ²⁺ /Li⁺相对于原始 CNT 膜，氨基-CNT 膜的选择性降低。还发现，虽然Mg ²⁺ /Li ⁺的选择性随着原始和羧基-CNT膜的外部驱动力而增加，但氨基-CNT膜随着驱动力的变化趋势相反。我们注意到，在所有考虑的情况下，安装有羧基的 CNT 膜提供了最佳的 Mg ²⁺ /Li ⁺分离效率，用于在孔口处携带负电荷。我们的发现可以促进高效分离Mg ²⁺ /Li ⁺的膜设计的发展。