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+/Mg2+, K+/Mg2+, and H+/Fe2+, 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.