Thermodynamics of actinide redox reactions in potassium phosphotungstate solutions

摘要

The paper represents the results of the investigation of kinetics and thermodynamics of the M(IV) reduction reactions (M=Am, Cm, Bk, Cf) and also those of the Am(V) disproportionation reaction and the reaction between Am(V) and Am(III) in aqueous solutions of potassium phosphotungstate, K10P2W17O61 (KPW). From experimental data the thermodynamic parameters of activated complex formation for the M(IV) ions reduction process through the chemical route have been calculated. Linear correlation has been ascertained between the Delta G(298)(not equal) values and the oxidation potentials of the M(IV)-M(III) pairs in KPW solutions and on this basis the estimation of the Delta G(298)(not equal) values has been made for U, Pu and Np. In the case of the Am(V) disproportionation and the reaction of the interaction between Am(V) and Am(III) ions the enthalpy component introduces the main contribution into the Delta G(298)(not equal) change. At the same time the contribution of the entropy component into the Delta G(298)(not equal) change in KPW solutions is considerably lower than for perchloric acid solutions. (C) 1998 Published by Elsevier Science S.A. [References: 13]