Solid-liquid extraction of the group 4 elements Zr and Hf, which are homologues of Rf ( = 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 ( d ) with TIOA and HCl concentrations. The d 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 d 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 89m Zr and 175 Hf 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 d 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 261 Rf ( 1/2 = 68 s) experiments.

In superheavy element chemistry, rapid single-atom chemistry combined with rapid identification via alpha-particle measurement is required to be performed. Herein, we propose a new protocol for rapid preparation of coprecipitates of superheavy elements with Sm hydroxide. The coprecipitation behaviors of Zr, Hf, and Th (homologues of element 104, Rf) with Sm hydroxide in aqueous ammonia (NH 3) and sodium hydroxide (NaOH) solutions were investigated by the conventional suction filtration method using 88 Zr, 175 Hf, and 228 Th radiotracers. The precipitation yields obtained by employing an aging time of only 10 s were consistent with those obtained after aging for 10 min, suggesting the rapid chemical reactions in the present coprecipitation. Approximately 100% coprecipitation yields of Zr and Hf were achieved in the solutions with dilute hydroxide concentrations, and the yields decreased with higher hydroxide concentrations. In comparison, the Th yield remained constant at almost 100% under all of the conditions. In addition, a semiautomatic suction filtration apparatus for rapid preparation of precipitated samples was developed and evaluated using the short-lived isotopes 89m,g Zr and 173 Hf, which were transported online from the nuclear reaction chamber by a He/KCl gas-jet system. Using this apparatus, sample preparation was completed within 80-120 s, and precipitation yields consistent with those determined on the basis of the manual method were obtained, suggesting the applicability of the present method to Rf experiment.

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We successfully observed the equilibrium state of the chemical reactions for superheavy elements on a one-atom-at-a-time scale; we investigated the time dependence of the extraction behaviour of element 104, Rf. The distribution coefficient of Rf in 9 M HCl was found to be higher than those of its homologous elements, probably due to differences in the chloride complexation of Rf.

Solvent extraction of the group 4 elements Zr and Hf, homologues of Rf (Z = 104), by triisooctylamine (TIOA) from hydrochloric acid (HCl) was performed by batch method using carrier-free radioisotope