膜科学与技术

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Study on the Li+/Mg2+ separation performance of
mix-charged nanofiltration membranes

Authors： QI Ting, WEI Xiaona, ZHONG Jing

Units： School of Petrochemical Engineering， Changzhou University， Changzhou 213164， China

KeyWords： mix-charged membrane; Li+/Mg2+ separation; nanofiltration membrane; polyamide; interfacial polymerization

ClassificationCode：TQ028.8

year,volume(issue):pagination： 2025,45(6):13-25

Abstract：

Abstract: With the rapid growth of lithium-based energy demand, the efficient separation of lithium and magnesium in salt lake brines with high Mg2+/Li+ ratios has attracted significant attention. Nanofiltrationmembranes, leveraging size exclusion and Donnan exclusion effects, have emerged as a promising approach for Li+/Mg2+ separation. However, conventional single-charged nanofiltration membranes generally exhibit low selectivity for Li+/Mg2+ separation. In this study, mix-charged nanofiltration membranes with asymmetric charge distribution (PEI/PIP-PA and PIP/PEI-PA) were successfully constructed via sequential interfacial polymerization. The results demonstrated that the mix-charged structure synergistically enhanced Li+/Mg2+ separation performance. Both mix-charged membranes achieved MgCl2 rejection exceeding 96.0%, with Li+/Mg2+ selectivity values of 59.7 for PEI/PIP-PA and 41.1 for PIP/PEI-PA, significantly superior to that of the single-charged PIP-PA membrane (9.2). Notably, the PIP/PEI-PA membrane exhibited excellent Li+ permeability and maintained stable performance during long-term operation. Through a two-stage nanofiltration process, the Mg2+/Li+ mass ratio in the simulated high Mg2+/Li+ ratio brine (Mg2+/Li+ mass ratio 63) was significantly reduced to 0.28, demonstrating strong application potential. This study provides a new strategy for developing high-performance nanofiltration membranes for Li+/Mg2+ separation.

Funds：

国家自然科学基金项目（22508021）; 江苏省自然科学基金资助项目（BK20240973）

AuthorIntro：

齐婷（1995-），女，安徽铜陵人，讲师，博士，主要从事膜材料与膜分离研究

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