Manganese recycling of spent lithium-ion batteries via solvent extraction

Abstract

• Recycling of spent LiNi 0.33 Mn 0.33 Co 0.33 O 2 (NMC) active material from lithium ion batteries. • Continuous extraction of manganese from synthetic leaching solution with 100 g/L D2EHPA. • Correlations for Sauter mean diameter and holdup. • Mass transfer for cobalt, manganese and nickel in a disc and doughnut column. • Influence of feed pH value on selectivity and extraction yield. 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 MnSO 4 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.