Selective Separation and Purification of Mn from Co and Ni in Waste Mobile Phone Lithium-Ion Batteries Using D2EHAP via Solvent Extraction Method

In this study, the separation of Mn from a solution containing Co and Ni using solvent extraction method was explored. Bis-2-ethylhexyl phosphoric acid (D2EHPA) as extractant was diluted in the kerosene (20 vol%), and the effect of temperature was examined at 25, 40, and 55 °C. With increasing the temperature, the value of ΔpH increased, which means that the separation has been improved. The average value of the extraction reaction enthalpy of Mn was calculated as 41.8 kJ. As the temperature rose from 25 to 55 °C, Mn extraction percent increased from 93.4 to 98.3 in pH 3, and from 82.5 to 91.7 in pH 2.6. The average value of the extraction reaction enthalpy of Co was calculated as − 16.15 kJ. With increasing the temperature, Co extraction percent decreased from 39.6 to 27.5 and from 18.8 to 11 in pH 3 and 2.6, respectively. Applying the slope analysis method, the stoichiometry of extraction reaction for three metallic ions was calculated as 4. To obtain more selectivity and purity, the separation of Mn from Co and Ni was conducted via a simple extraction-extraction-scrubbing process. For this purpose, the extraction stage pH was adjusted to 2.5 at first, which led to 84%, 8.6%, and 6.2% extraction of Mn, Co, and Ni, respectively. The stripping of the organic phase was performed at pH 1.0, and with aqueous to the organic ratio equal to 1 (1:1). The second extraction stage was conducted at pH 2.5 and subsequently a scrubbing process with concentrated Mn solution cause the extraction percent of Mn, Co, and Ni to reach 69.3, < 1, and < 0.5, respectively. Graphical Abstract