Lithium-ion batteries (LIBs) are dangerous to recycle, as they pose a fire hazard when cut and contain various chemical hazards. If recycled safely, LIBs provide a rich secondary source for metals such as lithium and cobalt, while reducing the environmental impact of end-of-life LIBs. Discharging the spent LIBs in a 5 wt.% NaCl electrolyte at room temperature enables their safe dismantling. A sludge was observed to form during the LIB discharging, with a composition of 34.9 wt.% Fe, 35 wt.% O, 17.7 wt.% Al, 6.2 wt.% C, and 4.2 wt.% Na. The average electrolytic solution composition after the first discharge cycle contained only 12.6 mg/L Fe, 4.5 mg/L Li, 2.5 mg/L Mn, and trace amounts of Ni and Co. Separating the active cathode powder from the aluminum cathode with a 10 wt.% NaOH leach produced an aqueous filtrate with an Al metal purity of 99.7%. The leach composition consisted of 9558 mg/L Al, 13 mg/L Li, 8.7 mg/L Co, and trace amounts of Mn and Ni. The hydrometallurgical sample preparation processes in this study enables the production of a pure black mass with less than 0.05 wt.% Co, 0.2 wt.% Li, 0.02 wt.% Mn, and 0.02 wt.% Ni losses from the active cathode material.

Lithium-ion battery (LIB) recycling has received continued interest in recent years due to its benefits, which include reducing the environmental impact of spent LIBs and providing a secondary source of valuable metals, such as Li, Co, and Ni. This paper characterized the Li separation with D2EHPA from citrate media as a function of pH and identified the optimal overall Li separation at a pH of 5.5. The Li separation was optimized at a pH of 5.5, with which it was concluded that 23 vol.% D2EHPA and an O/A ratio of 4 provided the best Li separation, for which 66.1% Li was extracted with 26.9% residual Mn, 6.8% Co, and 7.7% Ni in a single stage. The formation of a reversible hydrophobic third phase was identified during Li extraction at a pH of 5.5 or greater. Investigation of the third phase revealed that more than 99% of the Li, Co, and Ni were extracted to the third phase, while more than 69% of the Mn was extracted to the organic phase. STEM images of the third phase revealed a honeycomb-like structure, which was hypothesized to be a 2D mesoporous film caused by the insolubility of the organometallic complexes in the aqueous and organic phase.

The performance requirements of modern lithium-ion batteries (LIBs) necessitate the use of a number of scarce and strategically sensitive metals such as lithium and cobalt. Recycling end-of-life LIBs reduces the demand on the primary sources of these metals and helps reduce the environmental impact of LIB waste. Citric acid has proven to be an effective environmentally friendly and sustainable lixiviant; however, the formation of metal citrate complexes complicates subsequent metal separation processes such as solvent extraction. This study enhances the understanding of LIB metal separation from citric acid media by comparing the metal separation performance of phosphorus-based liquid-liquid extractants from a citric acid leach. The optimum Mn(II) extraction pH decreases as the extractant’s phosphorus oxidation state increases from phosphinic to phosphonic to phosphoric, due to the oxygen atoms that surround the central phosphorus atom. The maximum Mn(II) separation with Cyanex 272, PC-88A, and D2EHPA was observed at pHs of 6, 3, and 3, respectively. D2EHPA further provided the best separation of Mn(II) over Al, Co, Li, and Ni with separation factors of 137, 191, 118, and 601, respectively. No research is currently available on the metal separation performance of phosphonic (PC-88A) or phosphinic (Cyanex 272) organic extractants from citric acid media.Significance: This study is the first to investigate the use of phosphonic and phosphinic extractants for metal separation from citric acid leach solutions, towards using citric acid as an environmentally friendly lixiviant. The phosphoric extractant, D2EHPA, enabled successful and sequential separation and extraction of aluminium, manganese and lithium, making the process technologically feasible and attractive.

The increasing use of rare-earth elements (REEs) in renewable technologies such as electric vehicles and wind turbines is driving a rapid rise in their economic importance. This work investigated the separation of REEs (Nd, Pr, Sm, and Dy) from NdFeB magnets using high-performance solid-phase extraction chromatography. More than 99% of the REEs were extracted from an Fe-rich sulfate-based leach liquor using a three counter-current stage solvent extraction of 34.7 vol.% and O/A 1.5. The REE-loaded H₂SO₄ strip solution was separated into a high-purity Nd and Pr fraction from separate Sm and Dy fractions in a single stage using a D2EHPA-impregnated column and H₂SO₄ gradient elution.