Complexation thermodynamics and the formation of the binary and the ternary complexes of tetravalent plutonium with carboxylate and aminocarboxylate ligands in aqueous solution of high ionic strength

The stability constants of the binary and the ternary complexes of Pu4+ have been measured for certain carboxylate and aminocarboxylate ligands in aqueous solution of I = 5.0 M (1 M perchloric acid + 4 M ionic strength perchlorate media) and temperatures of 0–45 °C by the solvent extraction technique. The stability constants of the binary and the ternary complexes increased with increased temperature. The complexation enthalpy and entropy of the binary Pu–Ox and the ternary Pu–EDTA–Ox and DGA complexes indicated the stability of these complexes is due to the highly favorable entropy contribution while complexation enthalpies either oppose complexation or are weakly favorable.