Potential oscillation enhanced lithium ion pump membrane for lithium ion extraction

Abstract

In this work, a novel electrochemically switched ion permselective membrane (ESIPM) has been applied to the recovery of lithium from brine in the electrochemically switched ion permselective (ESIP) membrane separation system. This ESIPM was prepared by multi-layer assembly, with polyacrylonitrile ultrafiltration membrane (PAN) as the base membrane, and CNTs/CS membranes pressed and filtered on the base membrane as the current collector, crosslinking a lithium manganate/carbon black/polyvinyl alcohol/polyacrylic acid (LiMn2O4/C/PVA/PAA) composite material, which coated on a polyacrylonitrile ultrafiltration membrane/carbon nanotubes (PAN/CNTs) composite membrane as the electroactive lithium ion exchange layer. In the ESIP system, by alternately applying oscillation potentials between the ESIPM membrane and counter-electrodes to regulate the placement and release of the target ions on the membrane, Meanwhile the target ions are driven by the electric field to be enriched in the ESIPM and directionally transported through the ESIPM. As a result, it was found that compared with the electrodialysis (ED) system, the flux of Li+ in ESIPM in the ESIP system increased by 12 times and the selectivity factor for Li+/Mg2+ increased by 1.4 times for the brine with Mg2+/Li+=1. Besides, the selectivity factor for Li+/Mg2+ reaches 4.4 for the brine with Mg2+/Li+=20 in ESIPM in the ESIP system, which was 2.2 times higher than that of the commercial ion exchange membrane CIMS in the ED system.