Silica-supported ionic liquids as efficient materials to separate cobalt and nickel from lithium in aqueous solutions

Lithium (Li + ), cobalt (Co 2+ ), and nickel (Ni 2+ ) are critical elements used in various types of lithium-ion batteries, including those in electric vehicles and other industrial applications. Given the increasing demand for these materials and their risk of scarcity, it is important to develop technologies that can efficiently extract these metals from secondary sources, such as industrial effluents, rather than focusing solely on spent batteries. This study addresses the preparation and evaluation of an imidazolium-based supported ionic liquid (SIL) for the selective removal of citrate-coordinated Co 2+ and Ni 2+ from aqueous solutions, obtaining a solution predominantly containing Li + . Optimal sorption conditions were identified using Response Surface Methodology (RSM), with pH 7.8, 1.5 g/L SIL, and 0.4 mg/L metals yielding removal efficiencies of 95 % of Co 2+ and Ni 2+ in just 2 h. The SIL showed high performance in ultra-pure and bottled waters, but efficiency declined in saline matrices due to the competition with other ions. Ecotoxicity tests using the bioindicator species Mytilus galloprovincialis revealed no adverse effects at concentrations up to 1 g/L. These results demonstrate the SIL's potential for sustainable and selective recovery of critical metals from low-salinity industrial effluents and other secondary aqueous sources. • Co and Ni removal by an imidazolium-based SIL was optimized by design of experiments. • Removal optimization evaluated for different pH, sorbent dose and metal concentration. • Removals of Co and Ni from ultra-pure water achieved 95 % in just 2 h. • Biomarker analysis showed no toxicity of the SIL up to 1 g/L to M. galloprovincialis.