Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 47 (2014)

Development of rapid solvent extraction technique with flow injection
analysis for superheavy element chemistry
T. Koyama,＊1 N. Goto,＊1 M. Murakami,＊1,＊2 K. Ooe,＊1 H. Haba,＊2 S. Goto,＊1 and H. Kudo＊3

D = Aorg / Aaq

The results of using the FIA system and the shaking timein the batch experiments are shown in Figs. 2 (a) and (b),respectively. In the experiment using the FIA system, theextraction equilibrium was attained within a contact time ofapproximately 2 s. On the other hand, a shaking time of 40
min was needed to attain extraction equilibrium in the batch
experiment. This result shows that extraction equilibrium
can be rapidly attained using the FIA system. On-line
liquid-liquid phase separation was successfully performed
using the membrane phase separator in the FIA system.
Thus, the developed FIA system is applicable for thesolvent extraction experiments of superheavy elements withhalf-lives of several tens of seconds considering othertime-consuming steps such as dissolution and sample
preparation for -particle measurement.

Fig. 1. Schematic view of the FIA system.
(a)

102

(b) 2
10

●Without phase separator○With phase separator

101

101

DD

For the chemical investigation of superheavy elementswith atomic numbers ≥ 104, rapid chemical separation isneeded because they have relatively short half-lives. We
developed a solvent extraction system applying flow
injection analysis (FIA). This FIA system consists ofsolvent extraction and phase separation parts (Fig. 1). In thesolvent extraction part, aqueous and organic phases are
mixed in a tube with a very small inner diameter of
100–200 μm. Because of the large specific interfacial areaand short diffusion length in the tube, extraction
equilibrium is rapidly attained. In the phase separation part,on-line liquid-liquid phase separation is achieved with ahydrophobic poly(tetrafluoroethylene) (PTFE) membrane.
In this work, solvent extraction of 95gNb (T1/2 = 35 d) using
this system was investigated as a model experiment forelement 105, Db.
The 95gNb tracer was produced through the bombardmentof a natZr metal target foil with a 14-MeV proton beamsupplied by the RIKEN AVF cyclotron. The carrier-free95g
Nb tracer was prepared by the chemical separation fromthe target using an anion-exchange technique.1)
In the solvent extraction experiment using the FIAsystem, 5 M HCl solution containing 95gNb tracer and 0.1 M
Aliquat 336 in 1,2-dichloroethane solution were used asaqueous and organic solutions, respectively. The aqueousand organic solutions were pumped using double-plunger
pumps and mixed in a T-connector. The mixture was fed
into the extraction coil of the PTFE tube of inner diameter
0.17 mm, and on-line liquid-liquid phase separation wasperformed using the membrane phase separator of thickness
75 m and a 0.8-m pore size PTFE filter.
In order to evaluate the time needed for attaining
extraction equilibrium, the flow rate and extraction coillength were varied. After extraction, both solutions eluting
from the phase separator were collected in polypropylene
tubes. Experiments without the phase separator were alsoperformed. Batch extraction experiments of 95gNb using 0.6
mL of each phase were also performed for comparison withthe results obtained using the FIA system. The two
separated phases were then subjected to γ-ray spectrometry
using a Ge detector in all experiments. The distribution ratio(D) was calculated as the radioactivity ratio of each phaseby using the same flow rate (Eq.1).

100

100

10-10(1)

Graduate School of Science and Technology, Niigata University
RIKEN Nishina Center＊3
Department of Chemistry, Faculty of Science, Niigata University＊2- 275 -2
34Contact time/s

510-1020
4060
Shaking time/min

80Fig. 2. The dependence of D value of 95gNb on the contacttime in the FIA system (a) and the shaking time in the batch
experiment (b).
References1)＊11Y.

Kasamatsu et al : J. Nucl. Radiochem. Sci. 8, 69 (2007).