Advanced biomimetic nanofiltration membranes for lithium recovery with anti-janus charge structure
Yanrui Wang, Yaru Zhang, Meng Zhang, Shu Jiang, Xiaobin Tang, Heng Liang
Abstract
Nanofiltration (NF) membranes with high Li+/X2+ (Co2+, Mn2+, etc.) selectivity are crucial for cost-effective Li+ recovery, addressing the global lithium shortage. However, conventional positively charged NF membranes typically exhibit Janus structure, conferring low Li+ penetration and permeability, and are negatively affected by the electrostatic shielding effects. Inspired by the internal electrical structure of dust storms, where positive-negative mosaic-like charge structure generates strong electric fields to facilitate particle transport, this study proposes a discrete micro-nano isolated island strategy to regulate the charge distribution within the NF membrane. A quaternary ammonium electrolyte was designed to modify the NF membrane, enabling the development of anti-Janus membranes with mosaic-like charge structure. The resulting anti-Janus membranes demonstrated an exceptional Li+/X2+ selectivity, exceeding that of conventional PIP-TMC membranes by 647%-904%, with Li+ penetration at 84.99% and permeability at 20.72 LMH/bar. Furthermore, this study introduces an evaluation metric, Critical Efficiency Product (CEP), for specifically assessing Li⁺ recovery performance. Nanofiltration membranes with high selectivity for Li+ are crucial to address the global lithium shortage. However, the conventional membranes often have low Li+ penetration and permeability due to electrostatic shielding, making practical applications challenging. Here the authors report a membrane modified with a quaternary ammonium electrolyte for enhancing selectivity.