Abstract
Ion selective membranes with precise Mg2+/Li+ separation have attracted extensive interest in lithium extraction to circumvent the lithium supply shortage. However, realizing this target remains a significant challenge mainly due to a high concentration ratio of Mg2+/Li+ as well as the relatively close ionic hydration radius and chemical. Herein, inspired by the host-guest recognition between alkali-metal ions and crown ether (CE), a novel approach was proposed to regulate the membrane internal structure by introducing CE to strengthen the complexation between Li+ and CE. The CE modified membranes achieved the unique outcome of "Li+ rejection-Mg2+ permeation" deriving from enhanced solubility (KS) and retarded diffusivity (DS) of Li+ compared to that of Mg2+. The Mg2+/Li+ separation factors for MgSO4/Li2SO4 and MgCl2/LiCl of modified membranes (i.e., 20.1 and 17.7) are about 21.9 and 19.9 time higher than that of pristine membranes, respectively. The results from density function theory (DFT) indicated that the stronger host-guest interaction between CE and Li+ combined them closely, thereby increasing solubility and reducing diffusivity of Li+. Our findings develop a new efficient membrane-based strategy enabling the production of high-purity lithium salts from simulated brine.
Published Version
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