Electrochemical lithium extraction from desalination brine via lithium-manganese oxide intercalation electrodes in capacitive deionization

Abstract

The intensifying global demand for lithium necessitates the development of sustainable extraction pathways. Recovery of lithium from reverse osmosis (RO) desalination brine offers a compelling strategy to mitigate resource scarcity while valorising waste streams. This study investigates the application of capacitive deionization (CDI), an emerging electrochemical separation technology, for the selective recovery of lithium from RO brine solutions, emphasizing its low energy consumption and cost-effective operation. A lithium manganese oxide (LiMn₂O₄, LMO) sorbent was synthesized via a high-temperature solid-phase method and integrated as the cathodic material in a CDI cell operated at 1.1 V. The system was evaluated using a synthetic brine solution with a Li⁺/Na⁺ molar ratio of 1:30, representative of typical RO brine compositions. Comprehensive material characterization of the LMO employing scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) confirmed the successful formation of a spinel-phase structure with heterogeneous morphology of the prepared LMO. Under optimized operating conditions, the system achieved a lithium electrosorption capacity of 16.14 mg g⁻¹ , with minimal sodium uptake (0.02 %), demonstrating remarkable ion selectivity of lithium ions. These findings highlight the potential of CDI as a scalable and sustainable process for lithium recovery from saline waste streams. The integration of LMO-based CDI systems into desalination systems presents a dual-benefit approach, coupling water treatment with strategic resource recovery and advancing the principles of a circular economy.