RIKEN Accel. Prog. Rep. 50 (2017)

Ⅲ-3. Radiochemistry & Nuclear Chemistry

Extraction behaviors of Nb and Ta with triisooctyl aminefrom hydrochloric acid solution
R. Motoyama,䠆1,䠆2 K. Ooe,䠆1 Y. Komori,䠆2 M. Murakami,䠆3 H. Haba,䠆2 S. Goto,䠆1 and H. Kudo䠆4

䠆1

Graduate School of Science and Technology, Niigata University
RIKEN Nishina Center䠆3Japan Atomic Energy Agency
䠆4
Faculty of Science, Niigata University
䠆2- 250 -

D = (Aorg / Vorg) / (Aaq / Vaq),
where Aorg and Aaq are the radioactivities in the organic andaqueous phases, respectively, and Vorg and Vaq are thevolumes of the organic and aqueous phases, respectively.
The dependence of the D values of 90gNb and 178Ta
extracted into 0.12 M TiOA in xylene is shown in Fig. 1 asa function of the HCl concentration ([HCl]). The D valuesof both elements increase with increasing [HCl]. The D
values of 178Ta are greater than the values in the literature6)
for relatively high [HCl], although those of 90gNb are inagreement with those in the literature.6) It is presumed thatthe formed Ta complexes differ in the present experimentand reported experiment,6) which was performed on amacro scale. To obtain further information on the extracted
complexes of Nb and Ta and the differences between the Dvalues of Ta in the present experiment and the literature,6)
we need to conduct a detailed investigation. We will theninvestigate the behavior of Db and discuss the complex Dbformation mechanism.
103
10290g
178

NbTa

101
100

D

Of the studies of the 105th element, Db, only threereports have been published on the chloride complexes ofDb in the aqueous phase.1–3) In two of the reported
experiments, chloride complex formation and its extraction
behavior
with triisooctylamine(TiOA)
wereinvestigated.1,2) The observed sequence of the extraction
was Ta > Nb > Db > Pa. However the influence of fluoride
ions on the extraction sequence was suggested because amixed HCl/HF solution was used in the extraction.4) Only
one experiment using a pure HCl solution has been reported
so far, where a reversed-phase column chromatographic
experiment using 6 M HCl and Aliquat 336 on an inert
support was performed.3) The sequence of extraction was Pa> Nb Ӎ Db > Ta. This is a reversal of the earlier observed
sequence. To clarify the complex formation mechanism ofDb with chloride ions, it is important to study the behaviorof Db in pure HCl solutions.
We have already started investigating the extraction
behaviors of Nb and Ta as lighter homologues of Db frompure HCl solutions with TiOA on a tracer scale. As a resultof the liquid-liquid extraction using radiotracers 95gNb (T1/2= 34.991 d) and 179Ta (T1/2 = 1.82 y) preserved inconcentrated HCl after purification by ion exchange
separation with HF solution, the behavior of Ta, influenced
by the remaining fluoride ions, was observed.5) In this paper,
we report on the extraction behaviors of Nb and Ta using
radiotracers transported by a He/KCl gas-jet method, whichmakes it possible to observe the extraction behaviors ofthese two elements without the effects of HF.
Radiotracers of 90gNb (T1/2 = 14.60 h) and 178Ta (T1/2 =2.36 h) were produced in the natZr(d,xn) and natHf(d,xn)
reactions, respectively, using a 24-MeV deuteron beam
supplied by the RIKEN AVF cyclotron. Nuclear reaction
products recoiling out of the targets were transported by aHe/KCl gas-jet method at a He gas flow rate of 2.5 L/min.
The transported products were collected on a Naflon® sheet
for 1.5 min. The collected products were then dissolved in 1
mL of 2–10 M HCl. From this solution, 300 ȝL aliquots
were pipetted to a polypropylene tube in which 300 ȝL of
2–10 M HCl and 600 ȝL of 0.12 M TiOA in xylene hadbeen added. After shaking with a Voltex mixer for 10 min,the mixture was centrifuged for 1 min. From each phase,
420 ȝL aliquots were separated into sample tubes. The
radioactivity of each phase was measured with a Gedetector. We calculated the distribution ratios (D) of 90gNband 178Ta using the following equation:

10-1
10-2
10-3
10-4
02

4

6

8

10

12

[HCl]/MFig. 1. Distribution ratios of 90gNb and 178Ta extracted into
0.12 M TiOA in xylene as a function of the HClconcentration ([HCl]). Dashed lines indicate the values ofNb (blue) and Ta (red) reported in the literature. 6)
References
1) J. V. Kratz et al., Radiochim. Acta 48, 121 (1989).
2) H. P. Zimmermann et al., Radiochim. Acta 60, 11 (1993).
3) W. Paulus et al., Radiochim. Acta 84, 69 (1999).
4) V. Pershina et al., Radiochim. Acta 64, 37 (1994).
5) R. Motoyama et al., RIKEN Accel. Prog. Rep. 49, 238 (2016).
6) T. Ishimori et al., J. At. Energy Soc. Japan 3, 698 (1961).