Synergistic design of membrane-based ion separation and solar-driven evaporation for direct lithium extraction from salt-lake brine

Abstract The demand for lithium extraction from salt-lake brines is increasing to address the global lithium supply shortage. Nanofiltration membrane-based separation technology with high Mg 2+ /Li + separation efficiency has shown great potential for lithium extraction. However, it usually requires diluting the brine with a large quantity of freshwater in the pre-treatment stage and only yields Li + -enriched solution. Inspired by the process of selective water/ion uptake and salt secretion in mangroves, we report here the direct extraction of lithium chloride (LiCl) powder from salt-lake brines by utilizing the synergistic effect of ion separation membrane and solar-driven evaporator. The ion separation membrane-based solar evaporator is a sandwich structure consisting of an upper photothermal layer to evaporate water, a hydrophilic macroporous membrane in the middle to generate capillary pressure as the driving force for water transport, and an ultrathin ion separation membrane at the bottom to allow Li + to pass through and block other multivalent ions. This process exhibits outstanding lithium extraction capability. LiCl powder with a purity of 94.2% can be directly collected on the surface of the evaporator. When treating simulated salt-lake brine with ion concentration as high as 348.4 g L − 1 , the Mg 2+ /Li + ratio is reduced by 66 times (from 19.8 to 0.3). This research combines ion separation with solar-driven evaporation to directly obtain LiCl powder, providing a new and efficient approach for lithium extraction.