Radiopharmaceutical and hydrometallurgical separations of perrhenate usingaqueous biphasic systems and the analogous aqueous biphasic extraction chromatographic resins

Poly(ethylene glycol) (PEG)-based aqueous biphasic systems (ABS) and the an alogous aqueous biphasic extraction chromatographic (ABEC) resins have been investigated for the separation of perrhenate (ReO4-) from tungstate (WO42 -) in alkaline tungstate media for radiopharmaceutical application and for the separation of perrhenate from molybdate (MoO42-) in hydrometallurgical application. Salts of the water-structuring anions OH-, WO42-, and MoO42- f orm ABS by salting-out PEG, while chaotropic anions such as ReO4- and the s imilar TcO4- quantitatively partition to the PEG-rich phase in such ABS. Pe rrhenate can thus be separated from solutions high in WO42- and OH- concent ration, and the separation factors improve with an increase in the tungstat e or hydroxide concentration. In addition, the ReO4- anion can be separated from load solutions high in MoO42- and SO42-. Perrhenate can also be separ ated under similar conditions using ABEC resins in both batch and chromatog raphic modes. The retained ReO4- can be eluted from the column with a simpl e water strip. The chromatographic separation of ReO4- from WO42- provided 97% of the loaded ReO4- in 20 mt. Unlike traditional technetium generators which are adversely affected by high parent ion concentrations, higher conc entrations of the parent anion improve the retention of ReO4- onto ABEC res ins. After exposure of the ABEC resins to radiation doses as high as 500 Mr ad, an acceptable level of performance was maintained, although degradation of the resin (monitored using differential scanning calorimetry) was obvio us.