Efficient cobalt recovery and separation from spent batteries using a novel [TKN][Dca] ionic liquid

The ionic liquid tetrakis(decyl)ammonium dicyanamide ([TKN][Dca]) was investigated for the selective extraction of Co(II) from a simulated spent battery leachate, achieving efficient separation of Co(II) from Ni(II) and Li(I). [TKN][Dca] demonstrate a high Co(II) extraction efficiency in a 4 mol/L NaCl solution, without requiring pH adjustment. The separation factor ( β Co/Ni ) for [TKN][Dca] was determined to be 47433. Density functional theory (DFT) calculations and ESI-MS spectra revealed that the predominant anionic species involved in Co(II) extraction were [Co(Dca) 3-x Cl x ] − , with [Co(Dca)Cl 2 ] − and [Co(Dca) 2 Cl] − as the primary complexes. The strong coordination between the dicyanamide anion (Dca − ) and Co(II) enabled selective separation of Co(II) from the leachate. Co(II) was efficiently stripped from the loaded organic phase using Na 2 SO 4 , with the extraction efficiency after stripping comparable to that of fresh [TKN][Dca]. Furthermore, [TKN][Dca] exhibits excellent stability and maintained consistent performance over multiple extraction-stripping cycles, highlighting its potential for sustainable applications in metal separation fields.