Development of micro polymer inclusion beads (µPIBs) for the extraction of lanthanum

Abstract

Separation based on polymer inclusion membranes (PIMs) offers an attractive green alternative to conventional solvent extraction by reducing the amounts of extractants used and practically eliminating the use of diluents. Micro polymer inclusion beads (µPIBs) are similar or even identical in composition to PIMs but they are characterised by significantly higher specific surface area which leads to faster extraction and back-extraction.µPIBs composed of di-(2-ethylhexyl)phosphoric acid (D2EHPA) (30 – 80 wt%) as the extractant and poly(vinyl chloride) (PVC) or poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) (70 – 20 wt%) as the base polymer were fabricated via a novel phase inversion microfluidic method and applied to the extraction of La3+ for the first time. The highest D2EHPA concentration, which produced stable, homogeneous and spherical µPIBs, was found to be 60 wt% D2EHPA. La3+ could be efficiently extracted into these µPIBs from aqueous feed solutions at pH 2.5 and subsequently quantitatively back-extracted in a 0.3 M sulfuric acid receiving solution.µPIBs of a composition (45 wt% D2EHPA and 55 wt% PVC) identical to that of a PIM previously studied for the selective extraction of La3+ and having the same mass exhibited 6 times higher surface area and 4.4 times higher initial mass transfer rate in the extraction of La3+. These results clearly demonstrate the suitability of the newly developed µPIBs for the separation of La3+.