Solar-Driven Photothermal Membrane Distillation-Selective Electrodialysis for Sustainable Lithium Extraction from Salt-Lake Brines

High Resolution Image Download MS PowerPoint Slide The urgent global demand for lithium, driven by the rapid expansion of electric vehicles and renewable energy storage, calls for advanced extraction techniques from salt-lake brines, where lithium is abundant but complex ion compositions and water scarcity challenge conventional methods. The Salar de Atacama, one of the world’s most lithium-rich yet technically challenging brine deposits, exhibits extreme salinity (∼4.6 mol/KgH 2 O) and elevated Mg concentration (7.31 g L –1 ), which complicate lithium selectivity, increase energy demand, and exacerbate regional water scarcity. To overcome these barriers, this study introduces an integrated photothermal membrane distillation–selective electrodialysis (PhMD-S-ED) system that harnesses solar-driven interfacial heating and ion-selective membranes to enhance lithium–magnesium selectivity, recover freshwater, and reduce energy consumption for environmentally sustainable lithium extraction from hypersaline Atacama brines. The PhMD unit, using graphene oxide-modified polyvinylidene fluoride (PVDF) membranes under 1 sun solar simulation, increases transmembrane flux by up to 74% compared to dark operation, reaching 2.1 kg m –2 h –1 at 40 °C, achieving water recovery above 30% while significantly lowering thermal energy consumption by 52–59%. The S-ED system was operated using concentrated brines (4.6–6.4 mol/KgH 2 O) derived from the PhMD retentate, employing monovalent-selective membranes over a temperature range of 20–60 °C and limiting current densities (LCDs) between 11.2 and 11.9 A·m –2 . The best performance, with Li + /Mg 2+ selectivity reaching 19.7, was obtained at a brine concentration of 4.6 mol/KgH 2 O, a temperature of 20 ° C, and an LCD of 11.2 A·m –2 . Peak current efficiency of 82% was observed at 40 °C feed temperature, with a specific energy consumption as low as 1.9 × 10 kWh/kg Li + . By integrating solar-activated water evaporation with membrane-based selective ion transport, this approach significantly reduces freshwater dependency and enhances lithium separation from complex, magnesium-rich brines, thereby advancing scalable and environmentally viable extraction technologies.