Removal of Iron and Boron by Solvent Extraction with Ionic Liquids and Recovery of Neodymium Metal by Direct Electrodeposition

In this study, the mechanism of Fe3+ ion extraction was investigated in the tri-n-butyl phosphate (TBP)/triethyl-pentyl-phosphonium (P2225) bis(trifluoromethyl-sulfonyl)amide (TFSA) system. According to the performed analysis, the Fe3+ extraction is based on cation exchange with ionic liquids: [Fe3+](aq) + 3[TBP](IL) + 2 [P-2225][TFSA](IL) + [TFSA(-)](aq) <-> [Fe(TBP)(3) (TFSA)(3)](IL) + 2[P-2225(+)](aq) Moreover, the removal of Fe and B by continuous extraction was investigated. It was determined that nine extraction cycles led to the removal of all B and most of the Fe and increased the concentration of rare earth ions in the organic phase by a factor of 2.2.The electrochemical behavior of the extracted [Fe-(III)(TBP)(3)(TFSA)(3)] complex was investigated at 373 K, and two reduction steps were detected: [Fe-(III)(TBP)(3)(TFSA)(3)] + e(-) -> [Fe-(II)(TBP)(3)(TFSA)(3)] , E-0 = + 0.71V [Fe-(II)(TBP)(3)(TFSA)(3)] + 2e(-) -> Fe-(0) + 3[TBP], E-0 = -1.61V Based on these results, potentiostatic electrodeposition from an electrolytic bath was carried out at -1.75 V at 373 K after the ninth cycle of continuous extraction. Electrodeposits with 0.8-0.9 m diameter were recovered on the Cu substrate, and metallic Fe in these deposits was identified by their energy dispersive X-ray spectrometry (EDX) spectra. Finally, the effectiveness of solvent extraction and direct electrodeposition in the recovery process was demonstrated in this study.