Complexation of Tc(IV) with $$ {\text{SO}}_{4}^{2 - } $$ SO 4 2 - in NaCl Medium

Abstract

This work reports the experimental determination of the stability constant for the complexation of the Tc(IV) cation by $$ {\text{SO}}_{4}^{2 - } $$ at 1.0 mol·kg−1 ionic strength (NaCl) and pcH 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 99Tc and 35S, 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(HSO4)+ and TcOSO4, into the organic phase. The apparent stability constant log10 βapp for the complexation of Tc(IV) by sulfate was found to be 1.13 ± 0.04.