Refinement of brine for lithium extraction using ion concentration polarization

Abstract

• The ICP process shows separation of ions based on electrophoretic mobility. • Reduction of Mg 2+ :Li + is demonstrated with standard divalent ion exchange membrane. • The technical feasibility is compared with well-established electrodialysis platforms. The surge of electric vehicle deployment in response to the global climate crisis has marked tremendous increase in the demand of lithium-ion batteries. Lithium brine has gained much attention as a critical primary lithium resource over mineral sources due to cheaper processing and greater abundance. However, reducing the Mg 2+ :Li + ratio of brines remains a challenge, as magnesium contaminates lithium precipitates. Solar evaporation ponds are traditionally employed to concentrate Li and reduce Mg content to tackle this issue, but typically require 1–2 years to process a batch of feed solution, and require much land area disturbing the local environment near brine resources. Here we present a continuous, scalable ion separation technique for reducing the Mg 2+ :Li + ratio of brine as an alternative to solar evaporation. The device utilizes ion concentration polarization to induce a locally amplified electric field. The amplified electric field separates ions into streams according to electrophoretic mobility. We demonstrate reduction of a 25:1 Mg 2+ :Li + lab brine to below 10:1 Mg 2+ :Li + , which is an acceptable lithium production purity by industrial standards. Reduction of a 60:1 Mg 2+ :Li + to ∼ 10:1 and a 100:1 Mg 2+ :Li + brine to approximately 20:1 are also demonstrated. The system suffers a high specific energy consumption (8.804 kWh/g Li + for 25:1 reduction to 9:1) due to low lithium recovery (9.9%) and microfluidic system size. However, an economic scaling analysis shows that this work is within an order of magnitude of the state-of-the-art separation technologies in the literature after various process parameters are normalized. Ultimately, this work demonstrates a potential novel process for continuous lithium extraction from brines, which is a generalizable ion separation tool utilizing differences in electrophoretic mobility.