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

Abstract 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/KgH2O) 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/KgH2O) 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+/Mg2+ selectivity reaching 19.7, was obtained at a brine concentration of 4.6 mol/KgH2O, 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.