Development of a separation method for rare earth elements using LN resin
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Development of a separation method for rare earth elements using LN resin L. M. Arrigo1 · J. Jiang2 · Z. S. Finch1 · J. M. Bowen1 · C. L. Beck1 · J. I. Friese1 · L. R. Greenwood1 · B. N. Seiner1 Received: 11 September 2020 / Accepted: 4 November 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract The lanthanide elements and isotopes are analytes of significant interest for several nuclear-related fields, for example nuclear waste treatment, nuclear forensics, and nuclear safeguards. Chemical separation among these elements is uniquely challenging due to their nearly identical chemical properties. This difficulty in interelement separation can create obstacles for quantitative radiometric analysis, specifically for isotopes without distinct energy emissions easily measured by gamma spectrometry, e.g. 161Tb. This work presents an optimized method for the isolation of individual rare earth elements using LN resin. Keywords Lanthanides · Fission products · Chemical separations · Extraction chromatography · LN resin
Introduction Several rare earth elements (REE), defined here as the lanthanides and yttrium, are important analytes for characterizing samples related to nuclear data measurements, environmental monitoring, radioactive waste treatment, nuclear forensics, and nuclear safeguards [1–5]. Many lanthanide isotopes are produced during fission with their respective yields decreasing with increasing atomic number [6]. REE isotopes such as 141Ce and 147Nd have half-lives, cumulative fission yields, and decay structures compatible with quantitation by gamma spectrometry without the need for chemical separations from interfering fission products [6]. REE isotopes such as 91Y and 144Ce can be quantified from mixed fission products samples but the data quality and/or analysis timeline greatly benefit from removal of other fission products. REE isotopes like 153Sm, 155Eu, 156Eu, and 161Tb cannot be quantified from mixed fission product samples without chemical separations and/or advanced detector technologies. A variety of methods have been explored for separating REEs, such as ion exchange chromatography [7–9], highpressure ion chromatography (HPIC) [10], mesoporous * B. N. Seiner [email protected] 1
Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MSIN J4‑65, Richland, WA 99352, USA
AWE plc, Aldermaston, Reading RG7 4PR, UK
2
carbon materials [11, 12], and extraction chromatography [3, 13–17]. Of the extraction resins, the LN extraction resin from Eichrom Technologies has many attributes amenable to separations of radiologically complex sample types. The LN resin is composed of polymeric beads coated with the organic extractant di-(2-ethylhexyl)-phosphoric acid (HDEHP) and is commonly used in REE mining applications [18]. The REEs sorb to the resin in low molarity nitric acid and are sequentially eluted lightest (La) to heaviest (Lu) by increasing nitric acid concentration; tri-valent actinides Am and Cm elute with the light lanthanides Ce, Nd, and Pr while Y elutes wit
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