Nanofiltration Membranes With Positive Charge for Lithium Extraction From Salt Lake Brine: Design, Construction, and Separation Performance

ABSTRACT The demand for lithium (Li) resources has soared with the rapid development of the electric vehicle and energy storage industries. The efficient and green Li extraction from salt lake brine with a high Mg 2+ /Li + ratio has become a research hotspot. Compared with traditional negatively charged nanofiltration (NF) membranes, positively charged NF membranes (PCNFMs) significantly improve the separation efficiency of Li + /Mg 2+ with enhanced Donnan repulsion effect and electrostatic interaction. This paper elaborates in detail on various PCNFMs construction strategies, also analyzes the influence of each method on membrane structure, charge distribution, water flux and selectivity. In addition, this paper also summarizes the sources, characterization methods and action mechanisms of positive charges on the membrane surface. Finally, the challenges faced by PCNFMs in practical applications, such as high salt‐alkali adaptability and long‐term stability are looked forward to, aiming to promote PCNFMs from the laboratory to industrial applications and to provide technical support for the efficient and low‐carbon extraction of Li resources from salt lakes.