Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 51 (2018)

Reversed-phase chromatography for element 105, Dbwith Aliquat 336 resin from 2.7 M and 27 M HF solutions
D. Sato,∗1,∗2 M. Murakami,∗1 S. Goto,∗1 K. Ooe,∗1 R. Motoyama,∗1 K. Shirai,∗1 R. Yamada,∗1 S. Tsuchiya,∗5T. Moriyama,∗5 H. Haba,∗2 Y. Komori,∗2 S. Yano,∗2 A. Toyoshima,∗3 A. Mitsukai,∗3 K. Tsukada,∗3H. Kikunaga,∗4 and H. Kudo∗5Elements with atomic number ≥ 104 are called superheavy elements. As aqueous chemical studies for element105, Db, an anion-exchange experiment was performed
in 13.9 M hydroﬂuoric acid solution.1) However, thechemical species of Db in HF solution is not still clear.
We have been studying a liquid-liquid and a solid-liquid
extraction of Nb and Ta which are lighter homologues ofDb with Aliquat 336 in solutions of various concentration of HF.2,3) In the liquid-liquid extraction, univalentanionic complex of Nb and Ta were extracted, and it
was implied that the extracted species were [NbOF4 ]−or [NbF6 ] and [TaF6 ]− .2) On the other hand, the resultsof solid-liquid extraction with 52 wt% Aliquat 336 resin
lead indicated that the distribution coeﬃcients, Kd , of95g
Nb has the minimum value at 10 M HF, while thoseof 179 Ta gradually decrease with increasing HF concentration.3) Because the adsorption behaviors of Nb andTa diﬀered clearly, similarity with the homologues of
the character of Db could be clear by measuring thedependence of Kd values of Db on HF concentration.
Because the results of Nb and Ta of on-line experimentwere good agreement with those of batch experiment in
2.7 M and 27 M HF, it is suggested that the chemical
formation of Nb and Ta of on-line experiment is samewith that of batch experiment.3) Therefore, 2.7 M and27 M HF were decided as the condition of Db experiment. In this study, we performed experiments of areversed-phase chromatography experiment of Db with
2.7 M and 27 M HF.
The isotope 262 Db was produced in the 248 Cm(19 F,5n)262 Db reaction at the RIKEN K70 AVF cyclotron.
The small amount of nat Gd was induced in the Cmtarget in order to monitor the state of the experiment by measuring 170 Ta which was produced in thenatGd(19 F, xn)170 Ta reaction. The reaction products
transported by the He/KCl gas-jet system were deposited on the collection part in Automated Rapid
Chemical Apparatus (ARCA) for 60 s. Then, theproducts were dissolved in 2.7 M or 27 M HF solution and loaded on a small chromatographic column(1.6 mm i .d . × 7.0 mm height) ﬁlled with the 52 wt%
Aliquat 336 resin at a ﬂow rate of 1.0 mL/min. Theeﬄuent was collected into a Ta disk as a primary fraction. The adsorbed species on the column were stripped∗1∗2∗3∗4∗5Graduate School of Science and Technology, Niigata University
RIKEN Nishina Center
Japan Atomic Energy Agency
Research Center for Electron Photon Science, Tohoku University
Department of Chemistry, Faculty of Science, Niigata UniversityFig. 1. The dependences of the adsorption yields of Nb, Ta,Db on [HF]ini with 52 wt% Aliquat 336 resin.

with 6 M HNO3 /0.015 M HF solution at a ﬂow rate of1.0 mL/min. The eﬄuents was collected another Ta diskas a secondary fraction. The both quantity of the primary and the secondary fraction was 150 µL. These Ta
disks were heated to dry the solution by halogen lamp,
then they were picked up into the automated rapid α/SF
detection system, RIDER, by robot arm to measure theirradioactivities. The Db experiments were performed for
596 times in 2.7 M HF and for 950 times in 27 M HF.
The average chemical yields of 170 Ta were about 22% in
2.7 M HF and 18% in 27 M HF, respectively.
From the obtained α-spectra, the number of events
corresponding to 262 Db (Eα = 8420–8740 keV)4) in
2.7 M HF were 10 in the 1st fraction and 2 in the 2ndfraction. In 27 M HF, 24 events in 1st fraction and 3
events in 2nd fraction were observed. Considering thecontamination, the distribution of decay time and thebackground, the adsorption yields on the 52 wt% Aliquat 336 resin which were estimated by radioactivity
ratio were 15.4% in 2.7 M HF and 14.8% in 27 M HF,respectively. In Fig. 1, it was found that the adsorption
yields of Nb and Ta are almost 100% in the both cases of2.7 M and 27 M HF, while those of Db are very smaller
than those of homologues. In addition, the adsorption
yields of Db are almost constant to [HF]ini . Therefore, if
the Kd values of Db are estimated from the adsorption
yield, the dependence of Kd values of Db on [HF]ini isalso constant. Because the Kd values of Ta are decreased
with increasing [HF]ini ,3) the extraction behavior of Db
would not be like Ta at least. Therefore, it was suggested that the ﬂuoride complex formation of Db is notsimilar to that of Ta.
References
1) K. Tsukada et al., Radiochim. Acta. 97, 83 (2009).
2) D. Sato et al., RIKEN Accel. Prog. Rep. 47, 247 (2014).
3) D. Sato et al., JNRS, sorc 61, 3B09 (2017).
4) M. Murakami, Dr. thesis, Niigata Univ. (2015).

- 216 -