Efficient separation of Mg²⁺ and Li ⁺ remains a major challenge in the extraction of lithium from salt lake brine. In this work, an electro-nanofiltration (NF) process was employed to separate Mg²⁺ and Li⁺ from the MgCl₂/LiCl feed solution under a current density of 0–2.83 mA cm⁻² and at an operating pressure of 5 bar. The surface chargeability of the NF membrane under an electric field (EF) was investigated in detail by combination of the experiment and theoretical simulation. It was found that Mg²⁺ ions were almost completely rejected (no Mg²⁺ detected by an ICP-OES with a determination limit of 0.01 ppm). A high permeance of Li⁺ (0.55 molm⁻²h⁻¹) and a stable solution flux of 75 ± 2 Lm⁻²h⁻¹ were achieved. The separation performance was far better than the results reported in the literature until now. It was believed that high positive charges on the negative-charged NF membrane surface were in-situ reconstructed and enhanced with the increase in current density due to the complexion and enrichment of Mg²⁺ on the membrane surface, leading to the high rejection for Mg²⁺. The dehydration of Li ⁺ ions with a low hydration energy under EF promoted the permeance of Li⁺. This work provides a practical route for efficient separation of Mg²⁺/Li⁺, and would have a huge potential in the extraction of high-pure Li⁺ salt from salt lakes.

Mg ²⁺和Li  ^{+ 的}有效分离 仍然是从盐湖卤水中提取锂的主要挑战。在这项工作中，采用电纳滤 (NF) 工艺在0–2.83 mA cm ^-2的电流密度和 5 bar 的操作压力下从 MgCl ₂ /LiCl 进料溶液中分离 Mg ²⁺和 Li ⁺ . 通过实验和理论模拟相结合，详细研究了电场 (EF) 下 NF 膜的表面带电性。结果表明，Mg ²⁺离子几乎完全被排除（ICP-OES 检测不到 Mg ²⁺，测定限为 0.01 ppm）。高渗透力的李⁺ (0.55 molm ^-2 h ^-1 ) 和稳定的溶液通量为 75 ± 2 Lm ^-2 h ^-1。分离性能远好于迄今为止文献报道的结果。据认为，由于膜表面Mg ²⁺的络合和富集，带负电荷的 NF 膜表面上的高正电荷随着电流密度的增加被原位重建和增强，导致对 Mg 的高截留²⁺。 在EF下具有低水合能的Li ⁺离子的脱水 促进了Li ⁺的渗透。这项工作为有效分离镁提供了一条实用的途径。²⁺ /Li ⁺，在盐湖中提取高纯Li ⁺盐方面具有巨大潜力。