A chromatographic separation of neptunium and protactinium using 1-octanol impregnated onto a solid phase support

Abstract

We have developed a new chromatographic method to efficiently separate and isolate neptunium (Np) and protactinium (Pa), based on the selective extraction of protactinium by primary alcohols. The effectiveness of the new technology is demonstrated by efficient separation of 233 Pa from parent radionuclide 237 Np, using a hydrochloric acid mobile-phase medium. Our new approach reproducibly isolated 233 Pa tracer with a yield of 99 ± 1 % (n = 3; radiochemical purity 100 %) and enabled chemical recovery of 237 Np parent material of 92 ± 3 % (radiochemical [99 %) for future 233 Pa tracer preparations. Compared to previous methods, the new approach reduces radioactive inorganic and organic waste; simplifies the separation process by eliminating cumbersome liquidliquid extractions; and allows isolation of radiochemicallypure fractions in less than 1 h. Graphical Abstract 50 150 250 350 Energy, keV 237 Np 9 M HCl 233 Pa 1 M HCl 30 mL 60 mL 0 mL γ: 311 keV α: 4.8 MeV Energy,

Radiochemical analysis of protactinium speciation

“…Since 233 Pa has a relatively short t1/2, activity standards must be prepared from a 237 Np standard solution via ingrowth of 233 Pa. 11,60,101 A nominal standard solution of containing 37 kBq of 237 Np (Lot #1760-91) used for this study was purchased from the Eckert and Ziegler Radioisotopes (Atlanta, GA, USA) and diluted to working solutions as described by us previously. 8,101 For these studies, 233 Pa was extracted from the working solution of 237 Np using a method described by us previously, which employs an extraction chromatographic resin (Amberchrom CG-71ms, 50-100 µm) impregnated with of 1-octanol. 101 Briefly, a slurry was prepared of the 1-octanol resin beads (0.66 g/5 mL H2O), then a column was prepared by transferring the resin slurry (5 mL) to an empty plastic column (0.8 cm inner diameter).…”

“…8,101 For these studies, 233 Pa was extracted from the working solution of 237 Np using a method described by us previously, which employs an extraction chromatographic resin (Amberchrom CG-71ms, 50-100 µm) impregnated with of 1-octanol. 101 Briefly, a slurry was prepared of the 1-octanol resin beads (0.66 g/5 mL H2O), then a column was prepared by transferring the resin slurry (5 mL) to an empty plastic column (0.8 cm inner diameter). Prior to isolation of 233…”

“…Isolation of decay product standards ( 228 Th and 233 Pa) were obtained by routine extraction chromatographic procedures developed in our laboratory. 8,101 Briefly, 228 Th and 232 U were separated and purified by TEVA resin (Eichrom Technologies, LLC, Lisle, IL), where 228 Th can be eluted in 4 M HCl, while 232 U is retained and subsequently eluted with 0.1 M HCl. Separation and purification of 233 Pa and 237 Np was performed using a resin form of 1-octanol, where 237 Np can be eluted and collected in 9 M HCl, whereas 233 Pa is strongly retained and subsequently eluted with 1 M HCl.…”

“…However, much can be learned about the chemical behavior of Pa through observation of its behavior in chemical extraction systems at trace levels. 5,13,66,101 Previous research has suggested that aliphatic alcohols can effectively extract and separate Pa from the other actinides and fission products. 5,101 Interestingly, an aliphatic alcohol (octanol) is used as a diluent in some separation and extraction systems, suggesting that Pa might be unintentionally extracted at various separation steps.…”

“…5,13,66,101 Previous research has suggested that aliphatic alcohols can effectively extract and separate Pa from the other actinides and fission products. 5,101 Interestingly, an aliphatic alcohol (octanol) is used as a diluent in some separation and extraction systems, suggesting that Pa might be unintentionally extracted at various separation steps. 25 Whether research is occurring in industry, academia, or government, the experimental efficiency and careful planning are essential to ensure safe operations, while meeting financial and extraction objectives.…”