Complexation of Tc(IV) with SO42- in NaCl Medium

This work reports the experimental determination of the stability constant for the complexation of the Tc(IV) cation by SO 4 2 - at 1.0 mol·kg −1 ionic strength (NaCl) and p c H 1.51 ± 0.05, using a solvent extraction method. The data herein represent a first step in determining unknown thermodynamic parameters for the complexation of Tc(IV) by simple polyatomic anions. Radiotracer studies were carried out with 99 Tc and 35 S, using both HDEHP and TOPO as extractants, to characterize the mechanism of the solvent extraction and to examine the extraction of the competing species, TcO(HSO 4 ) + and TcOSO 4 , into the organic phase. The apparent stability constant log 10 β app for the complexation of Tc(IV) by sulfate was found to be 1.13 ± 0.04.