High-Purity Nickel Recovery from Low-Grade Nickel Laterite Ore Using Hydrophobic Diluted Deep Eutectic Solvents

With the expansion of the lithium-ion battery market, establishing new nickel supply routes is essential. One of the promising nickel sources is laterite ore, but the Mg-rich saprolite phase is rarely used as a battery material owing to its processing challenges. This study is the first to employ a hydrophobic diluted deep eutectic solvent (HDDES) for high-purity nickel recovery from saprolite. Diluting the DES reduces the inherently high viscosity, supporting faster leaching and improved ease of operation. The HDDES comprises a deep eutectic solvent (DES) composed of trialkylmethylammonium chloride and decanoic acid, which is diluted with Swasol 1800, an industrial diluting solvent. HCl loaded HDDES effectively suppressed Mg leaching while promoting efficient Ni leaching, and the HDDES exhibited high performance over five cycles. The metals in the HDDES were recovered by contacting with a water phase, and the Ni was further purified using alkaline solution, achieving 96.5% purity. HDDES is expected to serve as a novel leaching solvent in the field of metal refining, overcoming the drawbacks of conventional DESs.