Abstract
Brines are abundant waste products from desalination plants and have higher lithium contents than sea water (0.17 ppm). Herein, electrochemical lithium recovery from real brine solutions using Li-selective LiMn2O4 is reported. Free-standing electrodes are prepared completely solvent-free. At low current densities, the complete theoretical capacity of 148 mAh g(-1) can be utilized. The process is highly rate dependent due to the lithium concentration in the mm range. The high salt content of the brine depicts a challenging environment for electrodes and reactor materials. Competing earth-alkali metals lead to scale formation blocking the electrode surface and reducing the electrode capacity for lithium uptake. The high chloride concentration enables the formation of chlorine Cl-2 at potentials < 1 V versus Ag/AgCl competing with the deintercalation of lithium. A combination of commercial antiscalants was used to suppress the formation of CaCO3 at the electrode prolonging its cycle life. It is shown that a cation exchange membrane not only effectively blocks chloride ions from the electrode but also decreases the Li-diffusion. Finally, the selectivity of the process is proven in a real brine with a low lithium content (0.7 mm), and an actual recovery experiment is conducted in a flow setup.