THERMODYNAMICS OF ACTINIDE REDOX REACTIONS IN POTASSIUM PHOSPHOTUNGSTATE K10P2W17O61

The kinetics and thermodynamics of Me(IV) (Am, Cm, Bk, and Cf) reducti on, Am(V) disproportionation, and reaction of Am(V) with Am(III) in aq ueous solutions of potassium phosphotungstate K10P2W17O61 (KPW) were s tudied. The thermodynamic parameters of formation of the activated com plex in Me(IV) reduction by the chemical path (Delta G298(double dagge r), Delta H-double dagger, Delta S-double dagger) Were calculated. The linear correlation of Delta G(298)(double dagger) with the Me(IV)/Me( III) redox potential in KPW solutions was found, and the Delta G(298)( double dagger) values were estimated for U, Pu, and Np from this corre lation. The enthalpy component makes the major contribution to Delta G (298)(double dagger) of the Am(V) disproportionation and of the reacti on of Am(V) with Am(III). The contribution of the entropy component to Delta G(298)(double dagger) in KPW Solutions is substantially lower t han that in HClO4 solutions.