Recovery of metals from sulfate leach solutions of spent ternary lithium-ion batteries by precipitation with phosphate and solvent extraction with P507

Abstract

Sulfate leach solutions of spent ternary lithium-ion batteries (LIBs) contain transition metals (Mn, Co, and Ni) and Li in abundance. Selectively separating them from the sulfate leach solutions is necessary for their recovery. In this study, a novel approach was proposed for the selective separation and comprehensive recovery of these metals. The separation process was performed using stepwise phosphate precipitation and solvent extraction with P507. Firstly, 99.9% Al was selectively removed from the solutions through a phosphate precipitation process by adjusting the solution pH to 3.5 using NaHCO₃ and adding 1.1 times the theoretical dosage of Na₃PO₄ at 80 °C for 30 min. The percentage precipitation of the other metals was 2.34%. Thereafter, the solutions could be directly used for the co-extraction of Mn, Co, and Ni by P507, leaving Li in the raffinate. A total of remaining Mn, Co, and Ni were co-extracted through five-stage counter-current extraction using an organic system consisting of 1 mol/L P507 (saponification degree of 60%) in sulfonated kerosene with an O/A ratio of 1.4:1. The co-extracted Mn, Co, and Ni in the loaded organic system were completely stripped through three-stage counter-current stripping using 1.5 mol/L H₂SO₄ with an O/A ratio of 5:1. By this process, the obtained solutions of Mn, Co, and Ni can be directly used to prepare ternary material precursors for recovery, while only 3.05% Li was lost. Finally, 98.9% Li left in the raffinate was easily recovered via Na₃PO₄ precipitation.