Abstract: With the rapid development of new energy industry in China, the technology of lithium extraction from primary salt-lake brine is particularly important, but the coexistence of lithium ions with potassium ions and magnesium ions increases the difficulty of separation. Two-dimensional nanochannel membranes show good prospects in ion separation due to nanoscale channel structure, but the high instability of channels affects the separation performance and reduce efficiency. In this study, two-dimensional montmorillonite channel membranes were constructed by modifying montmorillonite nanosheets with sodium carboxymethyl cellulose (CMC). The results show that the interaction between CMC and the edge of nanosheets facilitates the assembly of small nanosheets into large nanosheets, which enhances the negative electronegativity of nanosheets surface, and facilitates the transport of cations. Meanwhile, the hydrophilicity of membranes are regulated and the channel expansion is limited to realize the control of channel height by adding CMC. In the salt-lake brine multi-ion separation test, the membranes show excellent ion separation performance, with a separation selectivity of 15.10 for Li⁺/Mg²⁺ and up to 60.30 for K⁺/Mg²⁺. In the monovalent ion separation test, the membranes show certain K⁺/Li⁺ separation selectivity, which provides technical support for the application of high-performance two-dimensional montmorillonite membranes in lithium extraction from primary salt-lake brine.

Key words: two-dimensional nanochannel membrane, montmorillonite, salt-lake brine, sodium carboxymethyl cellulose, ion separation