Constructing a suitable charged surface layer of nanofiltration (NF) membrane is one of the key challenges to achieve efficient Li⁺/Mg²⁺ separation performance with high Mg²⁺/Li⁺ mass ratio (W_Mg2+/Li+). Herein, we proposed a facile route, i.e., grafting the short chain amino-rich monomers (SCA, H(NHCH₂CH₂)_1-4-NH₂) instead of conventional amino-rich macro-monomers (ARM), to construct a separation layer with uniform positive charge on the surface of pristine polyamide (PA) NF membrane to achieve effective Li⁺/Mg²⁺ separation. The SCA grafted NF membrane (PA-g-SCA) retained a more uniform distribution of positively charged groups on the PA layer compared with ARM grafted NF membrane. The SCA grafted NF membrane exhibited a high rejection of Mg²⁺ and high permeation of Li ⁺ at the same time, leading to an extremely high separation factor for Li⁺/Mg²⁺ of 130 even in the W_Mg2+/Li+ of 200:1 in the feed, which greatly surpassed those reported. The pure water flux was 1.8 folds than that of the pristine NF membrane due to the hydrophilicity improvement. The results suggested that the distribution uniformity of positive charges could be the key to efficient Li⁺/Mg²⁺ separation of the NF membrane. Our study provided a facile and robust route to design and construct high Li⁺/Mg²⁺ separation performance NF membranes.

构建合适的纳滤膜带电表面层是实现^{高Mg 2+ /} Li +^质量比（W _Mg2+/Li+ ）高效Li + / Mg 2+ 分离性能的^{关键挑战之一}。在此，我们提出了一种简便的途径，即接枝短链富氨基单体（SCA，H(NHCH ₂ CH ₂ ) _1-4 -NH ₂ ）代替传统的富氨基大分子单体（ARM），构建原始聚酰胺 (PA) NF 膜表面具有均匀正电荷的分离层，以实现有效的 Li ⁺ /Mg ²⁺分离。与 ARM 接枝 NF 膜相比，SCA 接枝 NF 膜 (PA-g-SCA) 在 PA 层上保留了更均匀分布的正电荷基团。SCA 接枝 NF 膜 同时表现出对 Mg ^{2+的高排斥和对 Li +}的高渗透 ，导致即使在W _{Mg2+/Li+为 200 时，Li} ⁺ /Mg ²⁺的分离因子也高达 130 ： 1 在提要中，大大超过了报道的那些。由于亲水性的提高，纯水通量是原始纳滤膜的 1.8 倍。^{结果表明，正电荷的分布均匀性可能是高效 Li +} /Mg ²⁺的关键NF膜的分离。我们的研究为设计和构建高 Li ⁺ /Mg ²⁺分离性能纳滤膜提供了一种简便而稳健的途径。