Solid-liquid extraction of the group 4 elements Zr and Hf, which are homologues of Rf (Z = 104), and Th, a pseudo homologue, by triisooctylamine (TIOA) from HCl solutions was performed by batch method. After examining the time required to reach extraction equilibrium for these elements in various concentrations of TIOA and HCl, we investigated in detail variations in the distribution coefficients (Kd) with TIOA and HCl concentrations. The Kd values of Zr and Hf increased with increasing the HCl and TIOA concentrations, suggesting an increase in the abundance of the anionic chloride complexes of Zr and Hf. On the other hand, the Kd values of Th were low in all the HCl concentrations studied, implying that Th does not form anionic species dominantly. We developed a new automated batch-type solid-liquid extraction apparatus for repetitive experiments on transactinide elements. Using this apparatus, we performed solid-liquid extraction employing the radioactive nuclides 89mZr and 175Hf produced by nuclear reactions and transported continuously from the nuclear reaction chamber by the He/KCl gas-jet system. It was found that the distribution behaviors in 7–11 M HCl are almost constant in the time range 10–120 s, and the Kd values are consistent with those obtained in the above manual experiment. This result suggests that the chemical reactions in the extraction process reach equilibrium within 10 s for Zr and Hf under the present experimental conditions. It took about 35 s for the extraction using the apparatus. These results indicate the applicability of the present extraction using the developed apparatus to 261Rf (T1/2 = 68 s) experiments.
Part of this work was performed at the RI Beam Factory (RIBF) operated by RIKEN Nishina Center and CNS, University of Tokyo. We express our gratitude to the staff of RIBF for the production of 89g,mZr and 175Hf. We also thank the accelerator crew of RCNP for the production of 88Zr and 175Hf. This work was supported by JSPS KAKENHI Grant Number 23750082.
©2015 Walter de Gruyter Berlin/Boston