Evidence for the existence of complexes between Th(IV) and alpha-isosaccharinic acid under alkaline conditions

The complexation of Th(IV) with alpha-isosaccharinic acid (ISA) was studied under alkaline conditions (pH 12.8 and 13.3) by two complementary techniqu es. Using high performance ion exchange chromatography, evidence was found for the formation of complexes between Th(IV), Ca and ISA. In the presence of Ca, Th is assumed to coordinate with two ISA ligands and two Ca ions. Th e ratio between Th(IV) and ISA in this complex in the presence of Ca was co nfirmed by batch sorption experiments, in which the sorption of Th was stud ied as a function of the concentration of ISA. Moreover, it was shown in th ese experiments that, in the absence of Ca, a 1:1 Th:ISA complex is formed. Conditional stability constants for the formation of both complexes are ca lculated.