Fluoride Complexation of Rutherfordium (Rf, Element 104)

The distribution coefficient (Kd) of Rf on ion exchange resins at various HNO3/HF concentrations had been studied [1]. Rf was eluted at higher HF concentrations from CIX than Zr and Hf and rather resembled Th. Up to 1 M HF, Rf was not retained on the AIX also resembling its pseudo-homolog Th. Th is known to form no anionic fluoride complexes, while Zr and Hf are forming complexes of the type [MF6] 2in HF solutions and therefore can be resorbed on AIX resins. We have continued these studiesNow of Rf and on-line produced Hf by systemetically varying both the HNO3 and the HF concentration. If Rf is resembling Th, there should exist no concentration range in which Rf is adsorbed on the AIX. Rf was produced in the Cm(O,5n) reaction at the PSI Philips Cyclotron. A 730 μg/cm Cm target was bombarded with a 0.5 μApart O beam. The target contained 10% Gd thus producing simultaneously short-lived Hf isotopes. Rf and Hf were transported by a He(KCl) gas jet and collected for 90 s by impaction on a slider in the Automatic Rapid Chemistry Apparatus ARCA II. The residue was dissolved in 200 μl 0.1 M HNO3/x M HF (x variable) and fed onto the AIX. The effluent was evaporated to dryness as sample 1. In order to elute remaining Rf from the column, a second fraction (200 μl) was collected which is known to elute group 4 elements from the column (2 M HCl/0.01 M HF). This fraction was prepared as sample 2. 78-s Rf was detected by α-spectroscopy. The counting time was 12 min. Every 8th pair of samples was monitored by additional γ-spectroscopy to determine the distribution of Hf. From the ratio of the counting rates, the Kd values were calculated. The results are shown in in the table and are also plotted in the 3D graphs below (some values in the plot are interpolated). It is obvious that the behavior of Rf and Hf in the examined system are remarkably different. While the Kd values of Rf are varying strongly with both HF and HNO3 concentration, the dependence of the Hf Kd values on the acid concentrations is rather weak. [HNO3] [HF] log Kd (Hf) log Kd (Rf) 0.1 0.01 2.1 0.8 0.1 0.03 2.1 0.9 0.1 0.05 2.0 0.8 0.1 0.5 2.1 0.9 0.1 1 2.2 0.7 0.03 0.5 2.2 1.7 0.01 0.01 2.1 1.0 0.01 0.05 2.3 1.6 0.01 0.5 2.5 1.6 0.003 0.5 2.7 1.7 0 0.01 2.5 2.7 0 0.1 2.7 2.4 0 0.5 2.8 1.8 Table: log Kd values of Hf and Rf in different media