Peroxo-ligand coordination-driven selectivity enhancement for ta/Sb-Nb separation via MIBK extraction in HF-H2SO4 solution

Novel peroxo-complexation strategy was used to purify Nb-rich solution. • NbOF 5 2− transformation to NbO 2 F 5 2− greatly lowers its binding energy with MIBK. • Selectivity coefficient for Sb over Nb was enlarged by over 2300 times. • Nb 2 O 5 product met the high-purity specifications regarding Ta and Sb impurities. The efficient separation of Ta and Sb from Nb in hydrometallurgical processes remains a significant challenge due to their similar chemical behaviors. In this study, a novel peroxo-complexation strategy was introduced to enhance the selectivity of methyl isobutyl ketone (MIBK) extraction in an HF-H 2 SO 4 system. With the addition of H 2 O 2 , the extraction efficiencies of Ta and Sb reached 99.6% and 99.7%, respectively, while the co-extraction of Nb was only 2.32%. The selectivity coefficients of Sb/Nb and Ta/Nb significantly increased from 0.63 and 34.7 to 1461 and 6501, respectively. Stepwise stripping using H 2 SO 4 and pure water effectively recovered Nb and Ta/Sb from the loaded organic phase. Raman spectroscopy and quantum chemical calculations elucidated the mechanism of the enhanced separation selectivity. The peroxo-ligand selectively coordinates with Nb to transform it from NbOF 5 2− to NbO 2 F 5 2− , thereby weakening the negative surface potential of the fluorine atoms bonded to Nb. The binding energy between Nb ions and MIBK decreases from −172 kJ mol −1 to −104 kJ mol −1 , and thus the disparity in the affinity of Nb ions and Ta/Sb ions for MIBK is magnified. Overall, this peroxo-coordination approach provides an efficient and simple pathway for the effective purification of Nb solutions. Download: Download high-res image (176KB) Download: Download full-size image