High-capacity extraction chromatographic materials based on polysulfone microcapsules for the separation and preconcentration of lanthanides from aqueous solution

Extractant-loaded polysulfone (PS) capsules suitable for the separation and preconcentration of rare earth ions from acidic media have been prepared and characterized. Specifically, PS macro- and microcapsules have been impregnated with bis(2-ethylhexyl)phosphoric acid (HDEHP), and their performance in the extraction of europium (Eu3+) from nitric acid solution evaluated. The HDEHP-loaded microcapsules were found to exhibit sorption efficiency superior to those of analogous macrocapsules. Comparison to a conventional (i.e., commercial) extraction chromatographic (EXC) material (Ln center dot Resin), comprising HDEHP-loaded beads of poly(methyl methacrylate) (PMMA) of comparable size (50-100 mu m), showed that the capacity of the HDEHP-loaded microcapsules for europium is ca. 2.5-fold greater than that of the conventional material. This larger capacity is the apparent result of both the higher extractant loading achievable with the microcapsules and an unexpected change in the complexation stoichiometry of europium by HDEHP upon extractant encapsulation. The micro capsule-based sorbent equaled or exceeded the performance of the commercial EXC material in other respects as well, most notably uptake kinetics and column efficiency, making it a promising alternative to established EXC resins.