Rapid Separation of Individual Rare-Earth Elements from Fission Products

Abstract

A microprocessor-controlled radiochemical separation system has been developed to rapidly separate rare-earth elements from gross fission products. The system is composed of two high performance liquid chromatography columns coupled in series by a stream-splitting injection valve. The first column separates the rare-earth group by extraction chromatography using dihexyldiethylcarbamylmethylenephosphonate (DHDECMP) adsorbed on Vydac C 8 resin. The second column isolates the individual rareearth elements by cation exchange using Aminex A-9 resin with α-hydroxyisobutyric acid (a-HIBA) as the eluent. With this system, fission-product rare-earth isotopes with half-lives as short as ~ three minutes have been studied.

Solid-State and Solution-State Coordination Chemistry of Lanthanide(III) Complexes with α-Hydroxyisobutyric Acid

“…The pH was adjusted to 5 by adding 1 M NaOH and remained constant throughout the crystallization experiments. The pH of the HIBA solution was chosen to mimic the conditions of column chromatographic lanthanide separation as reported in the literature (pH varies between 3 and 5, the p K a of HIBA is 3.79). − The resulting solution was filtered through a 0.45 μm polyamide syringe filter and transferred to a 20 mL borosilicate scintillation vial, allowing for slow evaporation at room temperature until precipitation occurred. The ligand to metal ratio was varied from 1:1 to 4:1, with the most favorable crystallization conditions at 2:1.…”

“…The dual hydroxyl and carboxyl functionality enables various coordination modes for HIBA (Scheme ), in which the hydroxyl group could either be protonated or be deprotonated. Although HIBA has been utilized as an eluent to separate lanthanides and actinides for many years, − the eluted products in solution were generally not structurally characterized and information on the coordination of lanthanides with HIBA remains rare. Several researchers have reported that HIBA most likely forms negatively charged solution complexes with the lanthanides of the general formula Ln(HIBA) 4 – . − The trivalent lanthanides are assumed to adopt either a six-coordinate geometry with two HIBA acting as bidentate ligands (Scheme c or d) and the other two as monodentate (Scheme a or b) or an eight-coordinate geometry with four HIBA as bidentate chelating ligands.…”

Identification of a new isotope,168Dy

“…Details of this separation procedure are provided in [10] and [11]. Ten separate radiochemical separations of Dy were performed in the above manner.…”

ARCA II – A New Apparatus for Fast, Repetitive HPLC Separations

“…The microprocessor controlled Automated Rapid Chemistry Apparatus, ARCA [1] which is based on these principles has successfully been used in separations of Md, No and Lr as products from the 18 0, 22 Ne + 254 Es reaction [2] and in the search for superheavy elements [3,4], Set-ups which have some similarity to ARCA have been used earlier in studies of fission products [5,6] and also in heavy-element research [7]. In the course of our studies of the chemical properties of the element lawrencium [8,9] the ARCA system, as described in Ref.…”