Variation of stability constants of thorium citrate complexes with ionic strength

Citrate is among the organic anions which are expected to be present in the wastes planned for deposition in the WIPP repository. In this study, a solvent extraction method has been used to measure the stability constants of Th(IV) with citrate anions in aqueous solutions with (a) NaClO4 and (b) NaCI as the back-ground electrolytes. The ionic strengths were varied up to 5 m (NaCl) and 14 m (NaClO4). The data from the NaClO4 solutions at varying pH values were used to calculate thermodynamic stability constants through the use of Specific Ion Interaction Theory (SIT).