(469b) Lithium Recovery from Mixed Brines Using Membrane Distillation-Crystallization

The use of fossil fuels over the last century has altered the global ecosystem, causing health and environmental challenges as well as climate change. Due to increased concerns around these issues, coupled with the depletion of existing fossil fuel reserves, countries have adopted deadlines for transitioning away from fossil fuels to clean and renewable energy sources. This has led to the rise of electric vehicles and batteries, facilitating a large demand for lithium resources. Continental (salt lakes and salars), geothermal, and oilfield brines constitute about 66% of worldwide lithium sources, and these sources are typically more economical for direct lithium extraction than hard rock sources because they consume less water and produce a higher yield of lithium with fewer environmental impacts. However, the coexistence of different co-ions (i.e. K⁺, Na⁺, Mg^2+, and Ca²⁺) with the lithium makes extracting high-purity lithium from these sources challenging due to similarities in chemical properties. Previous studies on the separation of lithium from other ions through solvent extraction and nanofiltration have notable drawbacks in terms of corrosion of equipment and membrane fouling. Membrane distillation crystallization is a promising hybrid technology that combines MD with a crystallization system to produce pure water (by MD) and high-purity crystals (via the crystallizer). MD is a thermally driven process water vapor transfers through a porous, hydrophobic membrane that prevents transfer of the liquid and non-volatile solutes. The objective of this study was to utilize the MDC system to selectively recover lithium from mixed salt brines. The effects of crystallizer temperature and water recovery on selectivity of the MDC process are also explored to maximize lithium recovery. The MDC system was shown to effectively removed potassium (99.6%) and sodium (99.06%) from the mixed brine. Along with research results, the principles, mechanisms, operations, process parameters, and industrial applications of MDC will be discussed in-depth in presentation.