Chromatographic separation of selenium and arsenic: A potential (72)Se/(72)As generator

Abstract

An anion exchange method was developed to separate selenium and arsenic for potential utility in a (72)Se/(72)As generator. The separation of the daughter (72)As from the (72)Se parent is based on the relative acid-base behavior of the two oxo-anions in their highest oxidation states. At pH 1.5, selenate is retained on strongly basic anion exchange resin as HSeO4(-) and SeO4(2-), while neutral arsenic acid, H3AsO4, is eluted.

Keywords: As-72; Ion exchange; Radionuclide generator; Se-72.

Figure 1

Distribution coefficient for selenate, selenite, and arsenate as a function of pH (n = 6; the error bars are included).

Figure 2

Un-oxidized aliquot of the LANL-IPF sample evaluated on Dowex 1X-8 (100–200 mesh). Eluent of fractions: 0 = sample addition; 1–4 = water; 5–8 = 0.03 M HNO₃ (pH 1.5); 9–12 = 0.6 M HNO₃ (pH 0.2). Selenium is present in three different chemical forms: Se(0) in fraction 0; selenite in fractions 5–6; selenate in fractions 9–11.

Figure 3

Oxidation of LANL-IPF sample with 30% H₂O₂ evaluated on Dowex 1X-8 (100–200 mesh). Eluent of fractions: 0 = sample addition; 1–4 = water; 5–8 = 0.03 M HNO₃ (pH 1.5); 9–12 = 0.6 M HNO₃ (pH 0.2). Arsenate elutes in fractions 5 and 6, while selenate elutes in fractions 9–11.

Figure 4

Elution profile of generator column. Each elution included 0.03 M HNO₃(4 × 5 mL) followed by a water rinse (2 × 5 mL).

Figure 5

Se(VI) breakthrough comparison of irradiated and non-irradiated Dowex 1×8 resins. The columns were eluted with 0.03 M HNO₃ (4 × 1 mL) followed with a water rinse (4 × 1 mL).