Ⅲ-3. Radiochemistry & Nuclear Chemistry
RIKEN
Accel. Prog. Rep. 56 (2023)

RIKEN Accel. Prog. Rep. 56 (2023)

Extraction behavior of Nb and Ta in HF solution with F-form
TOMA resin
S. Goto∗1 and M. Higuchi∗1∗1

Kd for 95g Nb and 179 Ta were obtained from the following equation:
Kd =(Aini − Aa )/mr,Aa /Va(1)where the subscripts a and r represent the aqueous
phase and the resin, respectively, for the radioactivity
A, mass m, and volume V . Aini is the radioactivity
relative to the control sample.
According to the reported dissociation constant forhydroﬂuoric acid,4) the anions originating from HF aremostly HF−
2 at the concentrationns of HF in this study.
The dependence of Kd on the HF−
2 concentration isshown in Fig. 1. For both Nb and Ta, Kd was smallerin pure hydroﬂuoric acid than in the aqueous phase
containing Cl− . This may indicate a diﬀerence in theadsorption of Cl− and HF−
2 on the resin. However,further investigation is needed because the formationof complexes containing Cl is also possible when Clform resins were used.

106105

Kd / mL g–1

Elements with atomic numbers ≥104 are called superheavy elements. The purpose of Db chemistry research is to investigate the relativistic eﬀects of orbital
electrons, which are more pronounced in heavier elements. Furthermore, in the search for new elements, if
the anchor nucleus (last nucleus in the observed decaychain) is a neutron-rich Db isotope, the chemical identity of the Db can determine the formation of the newelement, because such isotopes have a relatively long
half-life.
Group 5 elements, including Db in hydroﬂuoric acid,form ﬂuorine-containing complexes very quickly, making this reaction system suitable for on-line chemical
experiments with short-lived Db isotopes. However,group 5 elements may also form oxyﬂuoride complexes,
thus a method to identify the chemical species is desired.1) We have studied solid-phase extraction of Nband Ta anion complexes from hydroﬂuoric acid using
Aliquat 336-supported resin.2) This extraction systemdiﬀers from anion exchange in that the distribution coeﬃcients of Nb is very diﬀerent from Ta; however, theextracted chemical species are not yet clearly known.
The resin used in this study was trioctyl methyl ammonium chloride (TOMA-Cl), one of the main components of Aliquat 336. The counter ions in Aliquat
336 and TOMA are generally chloride ions. In orderto clarify the eﬀect of chloride ions in solid-phase extraction with hydroﬂuoric acid, we prepared resins inwhich the chloride ion was replaced with an anion originating from the hydroﬂuoric acid, and investigated theextraction behavior of Nb and Ta.
Radiotracers, 95g Nb (T1/2 = 34.991 d) and 179 Ta(T1/2 = 1.82 y), were produced with deuteron irradiation on Zr and Hf metallic foil targets with natural isotopic abundance, respectively, using the RIKEN K70
AVF cyclotron. The radiotracers in the targets werechemically isolated by anion exchange. The 40-wt%
TOMA-Cl resin was prepared by mixing TOMA-Cl
dissolved in methanol with MCI GEL CHP20/P30 for
approximately 1 day.3) To obtain Cl− free F-type resin
the TOMA-Cl resin was shaken well with 10 M HF, andthen dried. A 400 µL of 1–27 M HF solution containing 95g Nb and 179 Ta tracers was shaken with approximately 11 mg of TOMA resin for 1 h using a syringeless ﬁlter. After ﬁltering the resin, the 250 µL solution
was aliquoted and the radioactivity was measured withan HPGe detector. Aqueous solution control samples
without resin were also measured to determine the radioactivity of the resin. The distribution coeﬃcients
Graduate School of Science and Technology, Niigata University- 141 -104
103
102
101
100 -21010-1100–[HF2 ] / M

101

Fig. 1. Dependence of the distribution coeﬃcients Kd forNb (black) and Ta (red) on [HF−2 ] with F-type (solidsymbols) and Cl-type (hollow symbols) TOMA resins.

References
1) O. L. Keller, Jr., Inorg. Chem. 2, 783 (1963).
2) D. Sato et al., RIKEN Accel. Prog. Rep. 50, 246 (2017).
3) H. Haba et al., Radiochim. Acta 95, 1 (2007).
4) H. H. Broene et al., J. Am. Chem. Soc. 69, 1644 (1947).