Extraction and recovery of cerium(IV) along with fluorine(I) from bastnasite leaching liquor by DEHEHP in [C_8mim]PF_6

摘要

BACKGROUND: Ionic liquids (ILs) as environmentally benign solvents have been widely studied in the application of solventextraction. However, few applications have been successfully industrialized because of the difficult stripping of metal ions orthe loss of components of the ILs. More work needs to be done to investigate the extraction behaviour of IL-based extractionsystems. In this work, the extraction behaviour of Ce(IV), Th(IV) and some trivalent rare earth (RE) nitrates by di(2-ethylhexyl) 2-ethylhexyiphosphonate (DEHEHP) in the IL, 1-methyl-3-octylimidazolium hexafluorophosphate ((C_8mim]PF_6),was investigatedand compared with that in the n-heptane system. In particular, the effect of F(I) on the extraction mechanism for Ce(IV) and itsseparation from Th(IV) was investigated. Otherwise, the recovery efficiency of Ce(IV) and F(I) from a practical bastnasite leachliquor was examined using IL based extraction. RESULTS: Similar selectivity (Ce(IV) > Th(IV) RE(III)) was observed in both the IL and n-heptane systems. The existence ofF(I) had a large negative impact on the extraction and separation of Ce(IV). An identical process for the extraction of Ce(NO_3)_4containing F(I) by DEHEHP in both IL and n-heptane was achieved under appropriate conditions. The Ce(IV) in the IL phase maybe quantitatively back extracted and may be recovered as part of high purity CeF_3and cerium sulfate.