A short review is given on our current anion-exchange studies of element 104, rutherfordium (Rf), in HCI and HNO3 solutions. The distribution coefficients of the Rf homologues Zr, Hf, and Th(IV), and Pu(IV) on an anion-exchange resin were measured in 1.0-11.5 M HC1 and 1.1-13.1 M HNO3 with a batch method using the radiotracers Zr, Hf, Th, and Pu. In experiments for the short-lived Rf, the isotopes Zr, Hf, and Rf were produced in the O-induced reactions on Ge, Gd, and Cm targets, respectively, and their anion-exchange behavior in 4.0-11.5 M HCI and 8.0 M HNO3 was investigated using the Automated Ion-exchange separation apparatus coupled with the Detection system for Alpha spectroscopy (AIDA). In the HCl system, the percent adsorption of Rf on the anion-exchange resin increases steeply with increasing HCl concentration from 7.0 M to 11.5 M. This adsorption behavior is similar to that of the group-4 elements Zr and Hf, and is quite different from that of the pseudo-homologue Th(IV). The percent adsorption decreases in the order Rf>Zr>Hf.In the HNO3 system, Rf behaves like Zr and Hf in 8.0 M HNO3 but not like Pu(IV) and Th(IV), implying the formation of cationic or neutral species.

Fluoride complexation of element 104, rutherfordium (Rf), produced in the 248Cm(18O,5n)261Rf reaction has been studied by anion-exchange chromatography on an atom-at-a-time scale. The anion-exchange chromatographic behavior of Rf was investigated in 1.9-13.9 M hydrofluoric acid together with those of the group-4 elements Zr and Hf produced in the 18O-induced reactions on Ge and Gd targets, respectively. It was found that the adsorption behavior of Rf on anion-exchange resin is quite different from those of Zr and Hf, suggesting the influence of relativistic effects on the fluoride complexation of Rf.