THE EXTRACTION AND STRIPPING BEHAVIOR OF HEPTAVALENT TECHNETIUM WITH TRIALKYL PHOSPHINE OXIDE

The solvent extraction of heptavalent technetium (Tc(VII)) from aqueous nitric acid by trialkyl phosphine oxide (TRPO) in kerosene has been studied. The effects of HNO3 and TRPO concentrations and temperature on the extraction of Tc(VII) were investigated. The extraction was found to proceed according to the reaction H+ + TcO4 + 2TRPO = HTcO4 . 2TRPO. The extraction enthalpy (AdeltaH), entropy (deltaSc). Gibbs free energy (deltaGe), and the apparent equilibrium constant (Kc) for the reaction are presented. Tc(VII) can also be effectively extracted from alkaline solution, but the distribution coefficient decreases with a decrease of alkalinity. A minimum value of the distribution coefficient of Tc(VII) appears at a pH value near 10. The Tc(VII) loaded in TRPO-kerosene can be efficiently stripped by deionized water, <0.1 g/L (NH4)2CO3, or