Use of ferric salt solutions as leaching agents of Co, Ni, Cu, Fe, and Mn from metallic alloys of spent lithium-ion batteries and separation of iron from the leaching solution

Smelting reduction of spent lithium-ion batteries (LIBs) results in metallic alloys containing Co, Ni, Cu, Fe and Mn. Dissolution of the valuable metals present in the metallic alloys is necessary to recover them. In this work, the mixture of Fe2(SO4)3 and FeSO4, single Fe2(SO4) and FeCl3 solutions were employed as leaching agents and the effects of parameters like ferric salt concentration, reaction temperature and time, and pulp density on the leaching of the metals were studied. The difference in the leaching percentage of the metals by the nature of the ferric solutions was insignificant. In these leaching systems, ferric and hydrogen ions act as oxidizing agents and sulfate/bisulfate and chloride anions as ligands. Optimum conditions for the complete leaching of metals by single ferric solutions were 0.35 mol/L Fe2(SO4)3 or 0.7 mol/L FeCl3 with 12.5 g/L pulp density for 60 min at 22oC. Addition of H2O2 to the leaching solution for the oxidation of Fe(II) to Fe(III) enhanced the selective extraction of iron over Co(II), Ni(II), Cu(II), Mn(II) and Si(IV) by D2EHPA. Stripping of iron from the loaded D2EHPA with aqua regia resulted in a pure iron solution. Compared to HCl and H2SO4 solutions, use of single ferric solution showed some advantages like fast reaction kinetics at 22oC and the reduction in dosage of acids and oxidizing agents.