Selective Extraction of Cu(II) from the Hydrochloric Acid Leaching Solution of Spent Lithium-Ion Batteries by a Mixture of Aliquat 336 and LIX 63

The smelting reduction of spent LIBs produces metallic alloys containing Co, Cu, Fe, Mn, and Ni. These metallic alloys can be completely dissolved by 2 M HCl solution containing H2O2 as an oxidizing agent. Extraction of the leaching solution with D2EHPA results in a Fe(III) free raffinate. In this work, solvent extraction experiments were performed with a mixture of Aliquat 336 and LIX 63 to separate Cu(II) from the Fe(III) free raffinate. This mixture showed selectivity for Cu(II) over Co(II), Mn(II), Ni(II), and Si(IV). The mixture of 0.3 M Aliquat 336 and 0.2 M LIX 63 had the highest synergistic coefficient for the extraction of Cu(II) from the solution. The Cu(II) in the loaded mixture was easily stripped by weak sulfuric acid solution, which facilitates the recovery of copper sulfate from the stripping solution. McCabe-Thiele diagrams for the extraction of Cu(II) by the mixture and for the stripping with sulfuric acid solution were constructed. Three stages of counter-current extraction and stripping experiments verified that only Cu(II) was completely extracted, and the purity of Cu(II) in the stripping solution was higher than 99.9%. Considering the selectivity and easy stripping of Cu(II) from the loaded organic, this mixture can be employed in real operation for the recovery of valuable metals from the leaching solutions of spent LIBs.