Nanofiltration membrane with crown ether as exclusive Li+ transport channels achieving efficient extraction of lithium from salt lake brine
Lithium extraction from salt lake brines with high Mg 2+ /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 ( [email protected] ) 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 [email protected] membrane with exclusive Li + transport channels provided by 15C5. The [email protected] membrane displayed a permeability of 8.0 L·m −2 ·h −1 ·bar −1 and stable separation factor ( S Li,Mg ) of 14, which could reduce Mg 2+ /Li + mass ratio of a simulated brine from 20 to 1.7. Furthermore, a three-stage NF process was designed and performed using a [email protected] membrane to separate a simulated salt lake brine, containing multiple ions and Mg 2+ /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 Mg 2+ with Mg 2+ /Li + mass ratio of 0.1. Therefore, this process could be applied to obtain Li 2 CO 3 products with high purity. Our investigation highlights the highly efficient Mg 2+ /Li + separation through NF membranes with exclusive Li + transport channels, potentially applicable to lithium extraction from salt lake brines with high Mg 2+ /Li + mass ratios.
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