Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 49 (2016)

Solventextraction
extraction ofof Zr
Zr andand Hf using
using the online flow-type
Solvent
flow-type extraction
extraction
apparatus
elements
superheavy elements
apparatus for superheavy
Y. Kasamatsu,䠆1 K. Nakamura,䠆1 T. Yokokita,䠆1 Y. Shigekawa,䠆1 Y. Yasuda,䠆1 N. Takahashi,䠆1 Y. Kuboki,䠆2 H. Haba,䠆2M. Murakami,䠆2 Y. Komori,䠆2 T. Yoshimura,䠆3 and A. Shinohara䠆1Thus far, ion-exchange and solid-liquid extractionexperiments have often been performed in solution
chemistry on superheavy elements.1) Solvent extraction
experiments were also conducted using rapid solvent
extraction apparatuses. However, sufficient distribution datafor discussion on complex formation were hardly obtainedin the extraction of short-lived superheavy elements
because it is difficult to achieve rapid equilibration andphase separation. Stable repetitive extractions and a-particle
detections are also difficult in online extraction experiments.
We developed an online flow-type solvent extraction
apparatus to accomplish rapid solvent extraction and phaseseparation with the short-lived 261Rf (68 s).2) In thisexperiment, by using the developed apparatus, weperformed the online solvent extraction of Zr and Hf(homologues of Rf) produced with the AVF cyclotron at
RIKEN to check the performance of the apparatus and to
search for suitable conditions of Rf experiments.
The developed extraction apparatus involves a reactor
tube (extraction unit, EU) filled with PTFE chips to mix
aqueous and organic solutions well (shortening of thediffusion length between these solutions is expected). Rapid
phase separation between aqueous and organic solutions
was achieved with a flow-type phase separator (PS) using aPTFE membrane filter. We found that separation with thepurity of each phase greater than 95% was accomplishedwith a 1-step separator. The entire setup of the online
extraction experiment at RIKEN is shown in Fig. 1. 89g,mZrand 173Hf were produced in the natSr(D, xn) and natYb(D, xn)
reactions, respectively. The nuclear reaction products wererapidly transported to the dissolution apparatus in thechemistry room by the He/KCl gas-jet system. The solvent
extraction of Zr and Hf was performed in a 7.8, 9.2, and10.4 M HCl/0.01 M Aliquat 336 carbon tetrachloride
solution system. 30-cm EU was used and the flow rate was
500 ȝL/min for both phases. The length of EU required toreach equilibrium was tested beforehand through an offline
extraction experiment using the apparatus. The eluted
aqueous and organic solutions were separately collected andVXEMHFWHGWRȖ-ray measurement, and the distribution ratios,
D (the ratio of metal concentration in organic solution tothat in aqueous solution), were determined.
The obtained D values are shown in Fig. 2. In this figure,the equilibrium D values obtained beforehand in the offline
batch extraction experiment are also shown for comparison.

The D values obtained in the present online experimentbasically match the tendency of the D values in equilibrium.
This result indicates that extraction equilibrium of thechemical reactions involved in the present solvent
extraction was achieved in the online experiment using theapparatus. At 9.2 M HCl, the D values of both Zr and Hf
were slightly lower than the equilibrium data. Repetitive
extraction was not performed in the present experiment.
Thus, these low D values might be due to uncertainty of thedata; if not, the length of the EU was insufficient (notequilibrated). We need to investigate the reproducibility ofthe data in the online experiment. The time taken toaccomplish one extraction procedure was approximately 1min, which is suitable for Rf experiments. In conclusion, wewere able to check the movement of the developed
apparatus and obtained the D values of Zr and Hf in anonline experiment.

Graduate School of Science, Osaka University
䠆2RIKEN Nishina Center䠆3
Radioisotope Research Center, Osaka University

1) M. Schädel, D. Shaughnessy: The Chemistry of Superheavy
Elements, 2nd ed. (Springer, Heidelberg, 2014).
2) Y. Kudou et al.: RIKEN Accel. Prog. Rep. 44, 262 (2011).

䠆1- 240 -Fig. 1. The entire setup of the online extraction experiment
at RIKEN

Fig. 2. The D values of Zr and HfReferences