Recovery of lithium carbonate crystals from a high salinity solution using membrane crystallizer with concentration and temperature gradients

The increasing global demand for lithium, driven by the rapid expansion of electric vehicles and energy storage systems, underlines the need for efficient lithium recovery technologies. This study explored the potential of using the fractional-submerged membrane distillation crystallizer (F-SMDC) process for recovering lithium carbonate (Li₂CO₃) crystals from high-salinity solutions. The F-SMDC integrates membrane distillation and cooling crystallization processes within a single reactor, utilizing concentration gradient (CG) and temperature gradient (TG) to enhance water recovery and resource crystallization. We investigated the behaviors of Li₂CO₃ crystallization, CG, and TG in presence of sodium sulfate (Na₂SO₄). Our results indicated that the low temperature-sensitive solubility of Li₂CO₃ is the current challenge for CG generation, as Li₂CO₃ crystallization tends to occur at the top of the reactor (at higher temperatures). Addition of Na₂SO₄ facilitated CG generation, improving the overall performance of the F-SMDC process for Li₂CO₃ crystallization at the bottom of the reactor. However, issues such as Li₂CO₃ crystal deposition on the membrane surface, changes in the CG tendency, and flux stabilization timing were observed. Thus, although F-SMDC shows promise for Li₂CO₃ recovery from high-salinity solutions, further process optimization is necessary to address the challenges of Li₂CO₃ crystallization and membrane fouling. Potential integration of additional crystallization techniques could enhance selectivity and recovery efficiency.