Reconstructed Polyamide Nanolayers via Two-Stage Interfacial Polymerization Engineering for Precise Ion Sieving

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Efficient lithium extraction from brines is crucial for sustainable energy, but challenging due to similar ion sizes and high salinity.
• Existing methods struggle with separating lithium (Li+) from magnesium (Mg2+) in complex brine matrices.

Purpose of the Study:

• To engineer a novel polyamide nanofiltration membrane for selective lithium extraction from high-ionic-strength brines.
• To achieve simultaneous structural and electrostatic control over the membrane's selective layer.

Main Methods:

• A two-stage interfacial polymerization strategy was employed to reconstruct the polyamide (PA) selective layer.
• Piperazine (PIP) adsorption-diffusion was regulated for nascent PA layer density and stability.
• A non-aqueous solvent facilitated the incorporation of a bidentate quaternary ammonium monomer for tunable positive charge.

Main Results:

• The reconstructed membrane featured a sub-nanometer selective layer with a tunable mild positive charge.
• Synergistic steric and electrostatic effects enabled effective Li+/Mg2+ discrimination, yielding separation factors exceeding 60.
• The integrated nanofiltration process achieved nearly 60-fold lithium enrichment from complex brines.

Conclusions:

• The developed membrane demonstrates practical applicability for lithium extraction from chemically demanding, high-ionic-strength brines.
• This study provides a molecular-level design framework for co-ion selective membranes.
• The findings advance membrane technology for sustainable resource recovery.