A potential DES-driven membrane applied in electrodialysis coupled extraction for the ultra-high separation of 7Li isotopes

In this work, a deep eutectic solvent (DES)-driven electrodialysis membrane material was constructed, with which an electrodialysis platform was first formed by coupling electrodialysis. Separation and enrichment of 7 Li + isotopes were carried out with the electrodialysis coupled extraction platform. Because of its lower binding energy barrier for forming complexes with 7 Li + , a β -diketone-driven DES composed of tri-n-octyl phosphine oxide (TOPO) and 2-thenoyltrifluoroacetone (HTTA) was introduced to the separation and enrichment of 7 Li + isotopes. Furthermore, DES extractant was used to prepare supported liquid membranes (SLMs) because of its ability to drive extraction, its liquid state at room temperature and its good hydrogen bond network. Compared with the reported extraction systems, the separation coefficient of 7 Li + / 6 Li + ( β 7Li/6Li ) reaches 1.173 at an applied potential of 1.0 V, which is now the highest known β -value in these reported extraction systems. The Gibbs free energy change (∆ G ) of the electrodialysis coupled extraction process reaches −395.996 J·mol −1 , which explains the preferred extraction of 7 Li + isotopes. The competition and enhancement mechanisms between electromigration and extraction in electrodialysis coupled extraction were investigated by studying the Li + concentration, separation coefficient of 7 Li + / 6 Li + and Gibbs free energy change of electrodialysis coupled extraction. The separation of 7 Li + isotopes via electrodialysis coupled extraction system has potential application in chemical engineering field.