Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 50 (2017)

Chelate extraction of zirconium and hafnium using flow injection analysis
technique for aqueous chemistry of element 104, rutherfordium
R. Yamada,䠆1 K. Ooe,䠆1 S. Goto,䠆1 H. Haba,䠆2 Y. Komori,䠆2 and H. Kudo䠆3
where A denotes the radioactivity of either 88Zr or 175Hf, andthe subscripts a and o refer to the aqueous and organic
phases, respectively.
Figure 2 shows the dependences of the D values of Zrand Hf on the contact time of the two phases in theextraction coil. The results obtained with the batch
extraction method are also shown in Fig. 2. The dashed andsolid lines in the figure show the D values of Zr and Hf,
respectively, at the extraction equilibrium. The D values ofZr and Hf obtained with the FIA apparatus increase more
rapidly than those obtained in the batch extraction, showingthat the extraction reaction was enhanced by the FIA
apparatus. However, extraction equilibrium was not attainedwith the FIA apparatus within the contact time of
approximately 1 min, which corresponded to the half-life of261
Rf (T1/2 = 68 s). Therefore, further enhancement of theextraction reaction through heating or vigorous agitation of
the two phases in the extraction coil is required.

Fig. 1. Schematic view of the FIA apparatus setup.

101

100

D

We have been investigating the solvent extraction
behavior of Zr and Hf, which are lighter homologues ofrutherfordium (Rf, element 104), with chelating agents
2-thenoyltrifluoroacetone(HTTA)
anddi(2-ethylhexyl)phosphoric acid (HDEHP). In our previous
study, the extraction mechanisms of Zr and Hf with TTA1)and HDEHP2) from 3 M acid solution were investigatedusing the batch method. The plots of the logarithm ofdistribution ratio (D) of Zr and Hf (log D) against log[TTA or (HDEHP)2] showed a linear relation with a slopeof approximately 4, suggesting that the extraction species ofZr and Hf were M(TTA)4 or M(HDEHP·DEHP)4 (M = Zror Hf). However, it took about tens of minutes to several
hours to reach extraction equilibrium with these chelatingagents. For extraction studies with a short-lived Rf isotope,more rapid extraction is required. In our previous study,3)rapid extraction equilibrium was attained using a flow
injection analysis (FIA) technique for the extraction of95g
Nbfromhydrochloricacid
intoAliquat
336/1,2-dichloroethane. In this study, we applied this rapid
solvent extraction apparatus for Zr and Hf extraction withHDEHP.
Radiotracers of 88Zr (T1/2 = 83.4 d) and 175Hf (T1/2 = 70 d)
were produced in the bombardment of metallic 89Y andnat
Lu foils, respectively, with a 24-MeV deuteron beamfrom the RIKEN K70 AVF cyclotron. These radiotracers
were chemically separated from the target materials throughanion exchange and the solvent extraction method. A
schematic view of the FIA apparatus used in this study isshown in Fig. 1. Three molar concentrations of perchloric
acid containing the tracers and 1.5 × 10-3 M HDEHP intoluene were used as aqueous and organic phases,respectively. These solutions were pumped withdouble-plunger pumps at the same flow rate of 0.10 or 0.50
mL min-1 and mixed in the extraction coil (Teflon capillary)with an inner diameter of 0.17 mm. The length of theextraction coil was changed from 0.5 to 10 m to vary thecontact time of the two phases. The aqueous and organic
solutions eluting from the extraction coil were collected in asample tube, which was subsequently centrifuged. The
aliquots of these two phases were separately pipetted into
other sample tubes and subjected to Ȗ-ray spectrometry
using a Ge detector. Because the flow rate of the aqueous
phase was the same as that of the organic phase, the Dvalues of Zr and Hf were evaluated from the following
simple equation:
D = Ao/Aa,:88
Zr (FIA):175Hf (FIA)88:175Zr (batch): Hf (batch)

10-1-2100.1

aq: 3 M HClO
4
org: 1.510-3 M HDEHP-toluene

0.5 15 1050100
Contact time or Shaking time / s500Fig. 2. Dependences of the D values of 88Zr and 175Hf on thecontact time in the FIA apparatus or shaking time in thebatch experiment. The dashed and solid line indicate the Dvalues of 88Zr and 175Hf at equilibrium, respectively.
References
1) A. Tanaka et al., RIKEN Accel. Prog. Rep. 48, 288 (2015).
2) R. Yamada et al., RIKEN Accel. Prog. Rep. 49, 241 (2016).
3) T. Koyama et al., RIKEN Accel. Prog. Rep. 47, 275 (2014).

䠆1

Institute of Science and Technology, Niigata University
䠆2
RIKEN Nishina Center
䠆3
Faculty of Science, Niigata University- 251 -