Advancing Lithium-Magnesium Separation: Pioneering Swelling-Embedded Cation Exchange Membranes Based on Sulfonated...

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Advancements in electrodialysis (ED) technology necessitate improved monovalent cation exchange membranes (CEMs).
• Existing CEMs exhibit low selectivity, challenging efficient separation of monovalent cations like Li+ and Mg2+.
• Limitations in current membrane materials and structures hinder selective ion transport.

Purpose of the Study:

• To design and synthesize a novel CEM with enhanced selectivity for monovalent cations.
• To investigate the structural, physicochemical, electrochemical, and selective ED properties of the designed membrane.
• To evaluate the membrane's performance in separating Li+ from Mg2+.

Main Methods:

• A swelling-embedded CEM was fabricated by integrating N-oxide zwitterionic polyethylenimine (ZPEI) into a sulfonated poly(ether ether ketone) (SPEEK) matrix.
• Membrane preparation involved reacting ZPEI with 1,3,5-benzenetrlcarbonyl trichloride (TMC).
• Systematic characterization and electrodialysis testing were performed to assess membrane properties and separation efficiency.

Main Results:

• The modified ZPEI-TMC/SPEEK membrane demonstrated significant permeability selectivity for Li+ over Mg2+ in binary systems.
• At 2.5 mA cm-2, ZPEI-TMC/SPEEK exhibited superior Li+/Mg2+ selectivity compared to commercial CEMs.
• The Li+ flux reached 9.78 × 10-9 mol cm-2 s-1 with a low Mg2+ flux of 2.7 × 10-9 mol cm-2 s-1, indicating potential for lithium-magnesium separation.

Conclusions:

• The developed ZPEI-TMC/SPEEK membrane offers a promising solution for selective Li+/Mg2+ separation via electrodialysis.
• The straightforward preparation process and innovative swelling-embedded structure provide methodological insights for advanced membrane design.
• The membrane shows potential for efficient and stable performance in lithium-magnesium separation applications.