The OECD/NEA TDB review on nickel

Nickel is present in radioactive waste (as activation products 59Ni and 63Ni) besides being an element widely distributed in the geosphere and considered for alloys in the engineered barrier systems for underground repositories. For these reasons, within the scope of the OECD Nuclear Energy Agency (NEA) Thermochemical Data Base (TDB) Project a comprehensive review of thermodynamic data has been carried out by the present authors [1]. Over 700 original bibliography sources have been considered, resulting in recommended data for over 50 inorganic species and compounds. Central to the new database are the selections for ΔfGm0(Ni2+, 298.15 K), established on the basis of re-evaluations of potentiometric data for Ni2+ | Ni (cr) and Sm0(Ni2+, 298.15 K) established on the dissolution equilibria for NiSO4.7H2O(cr). The resulting value for ΔfHm0(Ni2+, 298.15 K) is consistent with the values determined experimentally from the enthalpies of dissolution of NiX2(cr) (with X = Cl, Br, I). New experiments, providing precise determinations of these enthalpies and of the low temperature heat capacities of key solids such as NiCl2.6H2O(cr) would provide additional support to the current selections. As customary in this series of Reviews, solids and aqueous species with all groups in the periodic table have been considered. As an example of the use of the selected data, the figure shows the three-dimensional predominance diagram for the system Ni2+-CO2-H2O for a value aNi+2 = 10-4 (molal basis). [1] H. Gamsjaeger, J. Bugajski, T. Gajda, R. J. Lemire, W. Preis: Chemical Thermodynamics of Nickel, Elsevier, Amsterdam, (in press, to appear in 2005). (authors)