A 10 nm Polyamide Membrane with an Asymmetric Charge Structure for Efficient Lithium Extraction.

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Polyamide membranes are crucial for lithium extraction from salt-lake brines.
• Optimizing ion-sieving efficiency in these membranes is challenging.

Purpose of the Study:

• To develop an ultrathin polyamide membrane with enhanced ion-sieving efficiency for lithium extraction.
• To engineer asymmetric charge distribution and pore structure for improved Li+/Mg2+ selectivity.

Main Methods:

• Fabrication of an ultrathin polyamide membrane (∼10 nm) with low surface roughness.
• Engineering of a multi-layered structure with asymmetric charge distribution (positive upper, negative lower layer).
• Utilizing interlayer interpenetration to form a selective interfacial region with narrower pores.

Main Results:

• Achieved a high Li+/Mg2+ selectivity of 69 and a water permeation flux of 12 L m-2 h-1 bar-1.
• Demonstrated minimal fouling with over 90% flux recovery under high contaminant loads due to ultrasmooth surface and hydrophilicity.
• Scaled-up modules in a three-stage nanofiltration process significantly reduced Mg2+/Li+ ratio in brine simulant from 50 to 0.2.

Conclusions:

• The engineered polyamide membrane architecture effectively enhances lithium-ion selectivity and water flux.
• The membrane's properties make it highly suitable for industrial lithium recovery from brines with reduced fouling.
• This technology shows strong potential for efficient and sustainable lithium extraction.