Multipass Nanofiltration for Lithium Separation with High Selectivity and Recovery

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Nanofiltration (NF) is a sustainable technology for lithium (Li+) extraction from brines with high magnesium (Mg2+) concentrations.
• Single-pass NF processes exhibit a trade-off between Li/Mg selectivity and Li recovery, failing to meet industrial purity standards.
• Existing commercial and lab-made NF membranes lack sufficient Li/Mg selectivity for direct application in lithium extraction.

Purpose of the Study:

• To develop a multipass NF process with brine recirculation for enhanced lithium extraction.
• To overcome the selectivity-recovery trade-off in single-pass NF for high-purity lithium production.
• To demonstrate the potential of NF for efficient solute-solute separations.

Main Methods:

• Implementation of a multipass nanofiltration process incorporating brine recirculation.
• Experimental evaluation of a three-pass NF process using a commercial NF membrane.
• Theoretical analysis to predict performance of a four-pass NF process with brine recirculation.

Main Results:

• A three-pass NF process achieved a Li/Mg selectivity exceeding 1000, despite challenges with co-existing cations.
• Theoretical predictions indicate a four-pass NF process can reach Li/Mg selectivity over 4500 with >95% Li recovery.
• The proposed multipass NF strategy effectively addresses limitations of single-pass systems.

Conclusions:

• Multipass NF with brine recirculation offers a viable solution for high-purity lithium extraction from challenging brines.
• This approach significantly improves Li/Mg selectivity without compromising Li recovery.
• The developed process holds promise for advanced membrane-based separation technologies beyond lithium extraction.