Seawater is an abundant lithium source with a cumulative Li content of 230 billion tons. It is not a favorable resource to recover Li from, owing to its lower concentration (0.17 ppm) in seawater. Li concentration is significantly higher at 100-200 ppm in salt-lake brine and is the main source to commercially recover Li as of today. However, this resource is confined to specific geographical regions. In many countries worldwide, the principal water purification process is by reverse osmosis (RO) and salt concentration in RO brine is twice as that in seawater. Hence, in this study, we have shown that salt concentration in RO brine can be further concentrated up to 0.85 ppm by streamlining it with a direct contact membrane distillation (DCMD) unit. Novel LiAlO2 working electrode with a hybrid capacitor type activated carbon counter electrode pair in flow-through configuration to capture and release Li from the ultimate MD concentrate during charging and discharging cycle in sequential operation. XRD, XPS, and ICP measurements confirmed the crystal structure and elemental composition of the working electrode. At 0.5 mA cm-2, the recovered Li demonstrated above 97% purity, and the system was operated for 5 cycles without activity loss. Specific energy consumption for one Li recovery cycle was found to be ~10Wh/mol. Thus, the outcomes affirm the use of RO brine for valuable resource recovery in an energy-efficient approach.

Energy efficient Li recovery from concentrated RO brine using LiAlO2 film electrodes

ACS Spring Meeting 2021

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