Application of saponified D2EHPA for the selective extraction of manganese from spend lithium-ion batteries

Solvent extraction is used for the selective extraction of manganese from an industrial leaching solution based on active material from spent lithium-ion batteries. As solvent 100 g L-1 di-(2-ethylhexyl) phosphoric acid (D2EHPA) diluted in Isopar L and an addition of 5 vol% tributyl phosphate is used. D2EHPA is well studied for the separation of manganese from cobalt and nickel but no data can be found on the influence of saponification. The influence of the saponification degree on the extraction yield and selectivity is investigated for two extraction stages. An overall extraction yield of 98.7% is achieved. 40% saponified D2EHPA for the first and 20% for the second stage at a phase ratio of 2.33 shows the best performance in terms of extraction yield and selectivity. The saponification influences the pH shift during the extraction from initial 2.8 to 3.4.