Development of a novel selective extraction system for lithium and application to its secondary resources.

The rapidly increasing demand for lithium (Li) in electrified transportation and grid-scale energy storage necessitates the development of sustainable extraction technologies from unconventional resources. Seawater represents the largest Li reservoir on Earth, but its utilization is hindered by low concentration of Li and extremely high Mg/Li ratios, which impose stringent selectivity and process-efficiency constraints. Here, a self-solvating β-diketone method is described which enables an efficient Li recovery directly from natural seawater. In this approach, methyl isobutyl ketone (MIBK) functions simultaneously as extraction medium and intrinsic neutral donor, stabilizing Li complexes formed with dibenzoylmethane (DBM) under alkaline conditions and eliminating the need for external synergistic agents. Sequential alkaline preconditioning provided dual functionality by multivalent interfering ions separation and generating the active deprotonated β-diketonate ligand in situ. Under optimized conditions, the donor-free DBM-MIBK system achieved ∼90% Li extraction. The quantitative extraction was achieved even at low organic-to-aqueous phase ratio (i.e. O/A = 0.1) that reduced the solvent requirement by an order-of-magnitude relative to conventional β-diketone systems (O/A ≥ 1). Slope analysis confirmed the solvent participates in coordination and supports formation of a neutral Li(DBM)(MIBK)-type complex. Quantitative stripping of Li was carried out using dilute nitric acid. Solvent reuse conditions were optimized with five cycles that resulted in 90% reduction in the solvent requirement and progressive enrichment of Li in stripping solution. The achieved enrichment factor (PCF), limit of detection (LOD) and quantification (LOQ) of the proposed method were 9, 0.002 ng mL-1, and 0.008 ng mL-1 for 10 mL of seawater sample respectively. This method was validated with NIST SRM 181 (Spodumene) and spike recovery studies and applied to different secondary Li resources such as seawater, coal fly ash and spent Li-ion battery samples.