Synergistic extraction and separation of valuable metals from waste cathodic material of lithium ion batteries using Cyanex272 and PC-88A

Synergistic extraction and separation of cobalt (II), manganese (II) and lithium (I) from simulated sulfuric acid leaching of waste cathodic materials, using mixture of bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex272, HA) and 2-ethylhexyl phosphinic acid mono-2-ethylhexyl ester (PC-88A, HL) in n-heptane have been investigated. Extraction of Co2+, Mn2+ and Li+ follows the order as: Mn > Co ≫ Li independent on taking the single Cyanex272 or PC-88A or their mixtures as extractants. The possible extracted species are MA2·3HA or M(OH)A·3HA for single extractant (PC-88A and Cyanex272 are same) and MH3A2L3 for the mixed-extractant (M2+ is Co2+ or Mn2+). Cyanex272 + PC-88A shows an evident synergistic effect. The maximum synergistic enhancement coefficients, Rmax, are obtained for Co2+ (3.48) and Mn2+ (4.12) at the mole fraction XCyanex272 around 0.6 at pHe 4.95. Furthermore, the separation factors (Mn/Co) have been improved around two orders of magnitude upon adding EDTA into the synergistic extraction system. The entire stripping of Co and Mn can be achieved in one single stage when the concentration of hydrochloric acid or sulfuric acid is larger than 0.04 M or 0.01 M, respectively. Finally, a feasible process for recycling of spent cathodic materials of LIBs was proposed with industrial applications prospects.

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► Cyanex272 + PC-88A shows an evident synergistic effect for Co and Mn.
► The maximum synergistic coefficients, Rmax, are 3.48 for Co and 4.12 for Mn.
► Cyanex272 + PC-88A + EDTA can realize separation of Co, Mn and Li from each other.
► Entire stripping of Co and Mn can be achieved by H2SO4 ≥ 0.01 M or HCl ≥ 0.04 M.
► A feasible flowsheet for recovery of spent cathodic materials of LIBs was proposed.