Production of High Purity MnSO4·H2O from Real NMC111 Lithium-Ion Batteries Leachate Using Solvent Extraction and Evaporative Crystallization

Recovery of manganese as high purity MnSO₄·H₂O from purified NMC111 lithium-ion battery leachate using solvent extraction and evaporative crystallization was investigated. Bis(2-ethylhexyl) phosphoric acid (D2EHPA) was used for Mn extraction. Operational parameters for extraction, scrubbing, and stripping (e.g. pH, number of stages, phases composition) were determined based on the results of batch equilibrium experiments. Counter-current extraction in bench-scale mixer settlers (V_MSU=120 mL) was carried out with 35% v/v (1.05 M) D2EHPA in Isopar L operated at an average pH of 2.9 and θ = 1. More than 98% of the Mn was extracted in three counter-current stages together with 4%, 5% and 3% of Co, Li and Ni respectively. The distribution of impurities such as Zn, Ca, and Al was monitored during counter-current operations. Satisfactory removal of Co, Ni and Li from the loaded organic phase was achieved after contact with a solution of Mn 4 g/L (70 mM) in two stages at θ = 1. A solution with a Mn concentration of 8.7 g/L (160 mM) was recovered after stripping with 0.5 M H₂SO₄ at θ = 1 in two stages. Evaporative crystallization of the product allowed the recovery of high purity (99.6%) MnSO₄·H₂O. A flowsheet for Mn recovery from LIBs is proposed, and the advantages and challenges related to it are discussed.