Nanofiltration membrane with crown ether as exclusive Li+ transport channels achieving efficient extraction of lithium from salt lake brine

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 438; p. 135658
• Main Authors: Li, Hongwei, Wang, Ying, Li, Tingyu, Ren, Xiang-Kui, Wang, Jixiao, Wang, Zhi, Zhao, Song
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.06.2022
• Subjects: Crown ether; Exclusive Li+ transport channels; Mg2+/Li+ separation; Nanofiltration membrane; Three-stage nanofiltration process; Nanofiltration membrane; Crown ether; Mg2+/Li+ separation; Three-stage nanofiltration process; Exclusive Li+ transport channels
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2022.135658

[Display omitted] •Crown ether acts as Li+ transport channel in NF membrane for Mg2+/Li+ separation.•PEI@15C5-TMC membrane exhibits a high permeability and stable Mg2+/Li+ selectivity.•Three-stage NF process is exploited to reduce Mg2+/Li+ mass ratio from 50 to 0.1.•Li2CO3 product is extracted from simulated salt lake brine through NF process. Lithium extraction from salt lake brines with high Mg2+/Li+ ratios represents an effective alternative for tackling the scarcity of lithium resources. In this work, nanofiltration (NF) membrane with exclusive Li+ transport channels was designed and prepared through facile interfacial polymerization, in which polyethyleneimine (PEI) bonded with 15-crown-5 ether (15C5) through hydrogen interaction was selected as the aqueous monomer (PEI@15C5) and reacted with trimesoyl chloride (TMC). The channels generated by 15C5 molecules could facilitate Li+ transport owing to their affinity to Li+. Molecular dynamics simulation was conducted to further confirm the Li+ transport through PEI@15C5-TMC membrane with exclusive Li+ transport channels provided by 15C5. The PEI@15C5-TMC membrane displayed a permeability of 8.0 L·m−2·h−1·bar−1 and stable separation factor (SLi,Mg) of 14, which could reduce Mg2+/Li+ mass ratio of a simulated brine from 20 to 1.7. Furthermore, a three-stage NF process was designed and performed using a PEI@15C5-TMC membrane to separate a simulated salt lake brine, containing multiple ions and Mg2+/Li+ mass ratio of 50. After the treatment, the ultimate permeate solution of the third stage contained 24 ppm of Li+ and 2.7 ppm of Mg2+ with Mg2+/Li+ mass ratio of 0.1. Therefore, this process could be applied to obtain Li2CO3 products with high purity. Our investigation highlights the highly efficient Mg2+/Li+ separation through NF membranes with exclusive Li+ transport channels, potentially applicable to lithium extraction from salt lake brines with high Mg2+/Li+ mass ratios.