Abstract: Lithium is an important strategic mineral resource,but the development of high-performance membrane materials
for lithium extraction from salt lakes faces significant challenges. In this paper,a new type of two-dimensional montmorillonite
membrane for lithium-magnesium separation was prepared using natural layered mineral montmorillonite as raw material.
The separation performance and mechanism of the two-dimensional montmorillonite membrane were investigated by electrodialysis
technology,X-ray diffraction (XRD),atomic force microscopy (AFM),scanning electron microscopy (SEM),electrochemical
tests,and Fourier transform infrared spectroscopy (FTIR). The results indicated that two-dimensional montmorillonite
membrane exhibit excellent lithium-magnesium separation performance for typical raw brines from different salt lake regions in
China,with the lithium-magnesium separation selectivity all reaching above 10. Among them,the lithium-magnesium separation
selectivity for the raw brine of West Taijinar reach 14. 45,which is superior to that of commercial electrodialysis membranes.
Two-dimensional montmorillonite membrane have a more abundant water environment inside,which is conducive to weakening
the concentration polarization phenomenon during the ion separation process of the membranes. In addition,the channel height
(0. 53 nm) of the two-dimensional montmorillonite membrane is smaller than the hydrated diameters of lithium and magnesium
ions. Both lithium and magnesium ions need to be dehydrated to pass through the membrane,while magnesium ions are more
difficult to dehydrate than lithium ions,thus enabling highly selective separation of lithium and magnesium ions.

Key words: montmorillonite,two-dimensional nanochannel membranes,lithium extraction from salt lakes,electrodialysis,
lithium-magnesium separation