Positively charged Ti3C2Tx membrane for enhanced Li+/Mg2+sieving

Lithium extraction from salt lake is important for carbon neutrality, while obtaining both high Li+/Mg2+se- lectivity and high water permeance is still challenging. The burgeoning two-dimensional (2D) material membranes in decade show enormous potential to solve above problem due to its highly designable lamellar structure. In this work, a kind of positively charged laminated membranes using MXene nanosheets as building blocks with decoration of poly (diallyl dimethyl ammonium chloride) (PDDA) were proposed. Benefiting from the well- -intercalated PDDA between MXene nanosheets, the interlayer spacing between neighboring nanosheets was greater than 2 nm, which was conductive to enhance water permeance. Simultaneously, the introduction of PDDA endowed the membrane with positive charge, which exhibited sharply improved Li+/Mg2+selectivity by an order of magnitude due to enhanced Donnan effect. The prepared MXene/PDDA membrane with a modification mass ratio of 1:10 exhibited high Li+/Mg2+ selectivity of 29.3 with MgCl2 saline solution permeance of 9.8 L m- 2 h- 1 & sdot; bar- 1 and pure water permeance of 32.3 L m- 2 h- 1 & sdot; bar- 1 , which was promising for lithium extraction. Such membrane constructing concept could be expanded to other kinds of membranes based on 2D nanosheets for effective ion sieving.