Electronanofiltration Membranes with a Bilayer Charged Structure Enable High Li⁺/Mg²⁺ Selectivity

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Separating lithium (Li+) from magnesium (Mg2+) is challenging due to their similar ionic radii.
• Salt lake brines often have high Li+/Mg2+ ratios, necessitating efficient separation technologies for lithium extraction.

Purpose of the Study:

• To develop advanced electro-nanofiltration membranes (ENFMs) for enhanced Li+/Mg2+ separation.
• To improve lithium extraction efficiency from high-magnesium environments.

Main Methods:

• Sequential interfacial polymerization (SIP) was employed to construct bilayer charged ENFMs.
• Membrane surface charge was modulated by adjusting trimesoyl chloride concentration and introducing quaternized polyethylenimine.

Main Results:

• The optimized ENFMs exhibited a high Li+/Mg2+ selectivity of 49.85 and a Li+ flux of 4.10 × 10^-8 mol cm^-2 s^-1 at 10 mA cm^-2.
• The membranes maintained elevated Li+/Mg2+ selectivity (>45) in simulated brines with low lithium and high magnesium concentrations.

Conclusions:

• The developed bilayer charged ENFMs show significant promise for practical lithium extraction from challenging brine sources.
• The SIP approach offers a facile and effective strategy for fabricating high-performance membranes for ion separation.