Manganese recycling of spent lithium-ion batteries via solvent extraction

Solvent extraction of manganese was performed in a lab-scale DN50 pulsed disc and doughnut column. Optimal conditions for hydrodynamics and mass transfer were evaluated for the separation of manganese from cobalt and nickel with 100 g L-1 D2EHPA (di-(2-ethylhexyl) phosphoric acid) as a liquid ion exchanger. In performance tests with 0.01 mol L-1 MnSO4 solution a maximum extraction yield of 94% was achieved at a phase ratio of 1.2 and a pulsation intensity of 3.2 cm s−1. Statistical analysis showed that the column loading (12 and 24 m h−1) had no significant influence on the extraction performance. The feed was a synthetic leaching solution likewise from active material of spent Li-NMC (nickel-manganese-cobalt) ion batteries. It consisted of an equimolar solution of 0.01 mol L-1 cobalt, manganese and nickel sulfate. Highest extraction yields of manganese 84% resulted at a feed pH of 2.7 or higher. At a pH of 2.2 the selectivity had its maximum at 40 and 22 for Mn to Ni and Mn to Co, respectively. A feed pH of 2.7 is recommended for optimum extraction performance and selectivity.