Heptavalent rhenium, Re(VII), is often considered an acceptable analog for Tc(VII); use of stable Re instead of radioactive Tc would simplify experimental work. This study investigates the validity of the analogy for solvent extraction systems. Dual radioisotope-labelled liquid-liquid extraction (LLE) experiments were carried out incorporating both Tc-99m(VII) (with Tc-99(VII) carrier) and Re-186,188(VII) tracers (with stable Re carrier) in order to quantify the suitability of Re(VII) to act as an analog for Tc(VII). Extraction of each metal by tetraphenylphosphonium chloride in chloroform from a 1 M ionic strength aqueous solution was quantified. The distribution coefficient, D, of each metal was determined using gamma spectrometry and as a function of the extractant concentration (0.00 to 1.00 mM) and pH (0, 2, 4, 6, 8). The extraction equilibrium constant, Kex, was quantified for each metal. Results show that, while extraction of TcO4- was characterized by a greater Kex value than for Re(VII) extraction across the pH range, the trend of Kex as a function of pH was virtually identical for both metals. Additional LLE experiments using Re(VII) and Tc(VII) individually were carried out under identical conditions that were employed for the dual radioisotope-labelled samples. These results are in good agreement with the dual-metal LLE experiments. The extraction behavior of Tc(VII) and Re(VII) were also studied in perchlorate and nitrate media. Extractions in nitrate media showed a decrease in efficiency from chloride media, while extraction was essentially suppressed in perchlorate media.

Comparison the solvent extraction behavior of Re(VII) with Tc(VII)

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.