Zwitterion membranes for selective cation separation via electrodialysis

Lithium extraction from saline water by electrodialysis is an energy-efficient process. Herein, we examined a synergetic impact of amino isophthalic acid (AIPA) and the fixed quaternized groups to produce stable, cost-effective, and efficient zwitterion membranes (ZIMs) via a sol-gel process. We developed different membranes such as QAIPA-10, QAIPA-15, and QAIPA-20 by varying the amount of AIPA from 10 to 20 wt% in the base membrane. It was found that when the amount of AIPA increases, the Li + flux also improved from 1.66 × 10 −10 mol cm −2 s −1 to 33.46 × 10 −10 mol cm −2 s −1 , respectively. By comparing the membranes based on the various amounts of AIPA, the membrane with 20 wt% (QAIPA-20) had a higher Li + flux and reasonable permselectivity due to the high WU, CEC as compared with the QAIPA-10, QAIPA-15 and base membranes. To further explore the performance of the QAIPA-20, we also studied various cation systems such as Na + /Mg 2+ , K + /Mg 2+ , and H + /Fe 2+ , respectively. The obtained results proved that AIPA strongly dictates the cation transport channels, hydrophilicity, and repulsive centers of the ZIMs. We may conclude that QAIPA-20 is effective for lithium extraction, water desalination, and acid recovery.