Fully automated flow-by reactor for direct lithium recovery based on electrochemical ion pumping

The growing global demand for lithium, driven by the growth in electric vehicles and renewable energy storage systems, highlights the importance of efficient and selective extraction technologies. Electrochemical approaches, such as the electrochemical ion pump (EIP), offer a promising alternative to conventional processes. This study presents a fully automated, laboratory-scale lithium recovery system based on a flow-by reactor design. When operated continuously for over 1800 h and 120 cycles, the system was able to selectively extract lithium from synthetic geothermal brine using λ-MnO2 as the capture electrode and NiHCF as the counter electrode. In one long-term experiments with two phases, the reactor consistently produced a lithium concentration of 260 mM in 2 liter of recovery electrolyte, with a faradaic efficiency of 85% and average energy consumption of just 8.4 Wh per mol. However, a key limitation was identified in the form of retained liquid volume within the reactor, which constrains the maximum achievable lithium concentration in cyclic extraction processes. Selectivity analysis revealed that sodium co-extraction was primarily caused by back-mixing rather than ion intercalation. Increasing the flushing volume effectively reduced contamination, thereby improving selectivity. These results demonstrate the technical feasibility and scalability of EIP technology for direct lithium extraction (DLE), offering valuable insights into reactor design and process optimization for industrial implementation.