Lithium-Sodium Separation by a Lithium Composite Membrane Used in Electrodialysis Process: Concept Validation

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Global demand for lithium-ion batteries (LIBs) is increasing, stressing lithium resources.
• Extracting lithium from aqueous sources like salars and geothermal water is complex due to interfering cations (Na+).
• Existing separation methods require optimization for efficiency and selectivity.

Purpose of the Study:

• To investigate the efficacy of electrodialysis (ED) using a Lithium Composite Membrane (LCM) for selective lithium-sodium separation.
• To evaluate the impact of ED cell configuration, current density, and feed concentration ratio on membrane performance.
• To determine optimal conditions for lithium recovery and selectivity in a complex aqueous mixture.

Main Methods:

• Electrodialysis (ED) experiments were conducted using a two-compartment and a four-compartment cell with a pre-validated Lithium Composite Membrane (LCM).
• Li+/Na+ reconstituted solutions were used to test LCM performance in terms of lithium Recovery Ratio (RR(Li+)) and Selectivity (S(Li/Na)).
• Key parameters varied included current density and the feed concentration ratio of Na+ to Li+ ([Na+]F/[Li+]F).

Main Results:

• The four-compartment ED cell offered membrane protection but slightly reduced selectivity compared to the two-compartment cell.
• Increasing current density improved lithium recovery but decreased LCM selectivity.
• Optimal performance was achieved at a [Na+]F/[Li+]F ratio near 10, yielding >10% Li+ extraction with S(Li/Na) ~112 after 4 hours at 0.5 mA·cm-2.

Conclusions:

• Electrodialysis using LCM is a validated method for selective lithium extraction from sodium-rich aqueous solutions.
• The study identified optimal operating parameters for efficient lithium recovery and high selectivity.
• This process shows promise for sustainable lithium sourcing to meet the growing demand for lithium-ion batteries.