Scalable Single-Ion Selective Mixed Matrix Ion Exchange Membranes for Direct Lithium Extraction

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Electrodialysis (IEX) membranes are crucial for sustainable critical mineral recovery, including lithium from brines.
• Current membranes struggle with efficient lithium (Li+) and sodium (Na+) ion separation, showing poor Li+/Na+ selectivity.
• Growing demand for lithium, driven by electrification, necessitates improved separation technologies.

Purpose of the Study:

• To develop a novel mixed matrix (MM) ion exchange (IEX) membrane with enhanced Li+/Na+ selectivity for electrodialysis.
• To investigate the structural properties, stability, and ion transport mechanisms of the developed MM membrane.
• To address the critical need for cost-effective and energy-efficient lithium recovery from sodium-rich brines.

Main Methods:

• Fabrication of a LiMn2O4-incorporated mixed matrix (MM) IEX membrane using a quaternized poly(oxy-2,6-dimethyl-1,4-phenylene) matrix.
• Characterization of membrane structure using techniques like ICP and elemental mapping.
• Evaluation of membrane performance in diffusion dialysis and electrodialysis modes, assessing Li+/Na+ selectivity and ion flux.

Main Results:

• The MM membrane achieved near-infinite Li+/Na+ selectivity in electrodialysis, with Na+ below detection limits.
• Structural analysis confirmed homogeneous LiMn2O4 distribution, spinel-phase retention, and superior thermal stability.
• High Li+ flux was observed (46 ± 3 mmol·h-1·m-2 at Li+/Na+ ratio of 1), with no Na+ flux and no Mn leaching or degradation after repeated cycles.

Conclusions:

• The developed LiMn2O4-MM IEX membrane offers a highly selective and stable solution for lithium recovery from brines.
• This technology addresses the limitations of existing membranes, providing a sustainable and efficient pathway for critical mineral extraction.
• The membrane's performance supports the growing demand for lithium in electrification, offering a cost-effective and low-water-use separation method.