Selective membrane capacitive deionization for superior lithium recovery

To meet the huge demand of global lithium resources, it is urgent and challenging to develop a new efficient technology for lithium recovery from salt-lake brines. Here, we report a selective membrane capacitive deionization (sMCDI) system for the lithium recovery. Benefit from δ-MnO2-x@CNTs with efficient intercalated pseudo-capacitance and porous carbon with a specific area of 2989.2 m2 g−1, a high lithium recovery capacity of 43.0 mg g−1 is achieved in LiCl solution at 1.2 V, and the corresponding lithium recovery rate is 5.17 mg g−1 min−1. A modified Nafion® 212 membrane with thin LiMn2O4 coating is for the selective Li+ recovery. A much higher Li+/Mg2+ selectivity of sMCDI cell can be accomplished for dehydration by increasing the concentration of Li+ and Mg2+ in feed solution. When the concentration of Li and Mg in feed solution increases to 2420 and 26,487 mg L−1 (the Mg/Li mass ratio = 10.9), the Li+ and Mg2+ recovery capacity can reach 121.3 and 204.6 mg g−1, respectively, and the Mg/Li mass ratio decreases to 2.33 in recovery solution. These investigations expand the selection range of the available CDI electrode candidates, and offer the prospect of the sMCDI technology for the efficient lithium recovery from brines.