Nanofiltration Membranes Modified with a Clustered Multiquaternary Ammonium-Based Ionic Liquid for Improved...

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Growing demand for lithium in the energy sector exacerbates supply shortages.
• Existing polymer nanofiltration membranes lack selectivity for lithium extraction from Mg/Li mixtures due to pore structure and unstable surface charges.

Purpose of the Study:

• To synthesize a novel ionic liquid monomer (DABIL) and functionalize a polyamide thin-film composite (TFC) membrane for improved lithium separation.
• To enhance surface charge stability, hydrophilicity, and pore structure of TFC membranes for selective lithium recovery.

Main Methods:

• Synthesis of N¹-(6-aminohexyl)-N¹,N¹,N⁶,N⁶,N⁶-pentamethylhexane-1,6-diaminium bromide (DABIL) ionic liquid monomer.
• Covalent anchoring of DABIL onto a pristine polyamide TFC membrane via secondary amidation.
• Molecular dynamics simulations to understand surface property dominance by water-ion interactions.

Main Results:

• DABIL-modified membrane showed a sixfold increase in water permeability compared to the unmodified membrane.
• Achieved an improved Li⁺/Mg²⁺ selectivity of 26.49, outperforming state-of-the-art positively charged membranes.
• Demonstrated efficient antibacterial activity, mitigating biofilm formation.

Conclusions:

• Functionalizing TFC membranes with ionic liquids containing multication side chains is a promising strategy for sustainable critical metal recovery.
• The DABIL-modified membrane offers enhanced permselectivity and stability for lithium extraction from Mg/Li mixtures.
• This approach contributes to overcoming lithium supply challenges for the energy sector.