Fine-Tuning 2D Heterogeneous Channels for Charge-Lock Enhanced Lithium Separation from Brine

Abstract

The extraction of lithium (Li) from complex brines presents significant challenges due to the interference of competing ions, particularly magnesium (Mg²⁺), which complicates the selective separation process. Herein, a strategy is introduced employing charge-lock enhanced 2D heterogeneous channels for the rapid and selective uptake of Li⁺. This approach integrates porous ZnFe₂O₄/ZnO nanosheets into Ag⁺-modulated sub-nanometer interlayer channels, forming channels optimized for Li⁺ extraction. The novelty lies in the charge-lock mechanism, which selectively captures Mg²⁺ ions, thereby facilitating the effective separation of Li from Mg. This mechanism is driven by a charge transfer during the formation of ZnFe₂O₄/ZnO, rendering O atoms in Fe-O bonds more negatively charged. These negative charges strongly interact with the high charge density of Mg²⁺ ions, enabling the charge-locking mechanism and the targeted capture of Mg²⁺. Optimization with Ag⁺ further improves interlayer spacing, increasing ion transport rates and addressing the swelling issue typical of 2D membranes. The resultant membrane showcases high water flux (44.37 L m⁻² h⁻¹ bar⁻¹) and an impressive 99.8% rejection of Mg²⁺ in real brine conditions, achieving a Li⁺/Mg²⁺ selectivity of 59.3, surpassing existing brine separation membranes. Additionally, this membrane demonstrates superior cyclic stability, highlighting its high potential for industrial applications.