A preliminary study of polymer inclusion membrane for lutetium(III) separation and membrane regeneration

Abstract

This paper reports on the selective transport of Lu(III) from La(III) and Sm(III) through a polymer inclusion membrane (PIM) composed of 40 wt% di(2-ethylhexyl) phosphinic acid (P227) and 60 wt% poly(vinylidene fluoride) (PVDF). Basically, the changes in surface morphology, thickness and water contact angle of this PVDF-based PIM containing P227 (P227@PVDF PIM) with different polymer concentrations were investigated. By solvent extraction experiments, it is found that Lu(III) can be selectively extracted from La(III) and Sm(III) at pH 1.5 in hydrochloric acid solution. According to this result, P227@PVDF PIM was used to selectively transport Lu(III) from hydrochloric acid feed solution containing similar concentration of La(III) and Sm(III). The recovery factor of Lu(III) is 91% after 36 h, and about 5% of Sm(III) was also transported through the PIM. The concentration of La(III) in the feed solution and the stripping solution does not change. Furthermore, to overcome the ubiquitous decline of transport efficiency caused by the loss of carrier or the damage of membrane structure after long-term use of PIMs, a process for regenerating PIMs was first proposed and implemented. By comparison of the regenerated PIM with the normal PIM, there is almost no difference in the SEM image, ATR-FTIR spectrum and Lu(III) transport efficiency. It is expected that P227@PVDF PIMs have the potential to be applied to the grouped separation of rare earth elements (REEs), and this study also can be as an inspiration for the further study on the PIMs regeneration process.