Hydrolysis of dioxouranium(VI): a calorimetric study in NaClaq and NaClO4 aq, at 25 °C

We report the results of a calorimetric study on the hydrolysis of UO22+ in different ionic media (NaClO4 aq, NaClaq) at 25 °C. Experiments in NaCl were performed at different ionic strength, at I≤1 mol l−1. The species considered in both ionic media were UO2(OH)+, (UO2)2(OH)22+ and (UO2)3(OH)5+, and in addition (UO2)3(OH)42+ and (UO2)3(OH)7− in NaClaq. The dependence on ionic strength of enthalpy changes in NaClaq was expressed by the simple linear equation ΔHpq=ΔH°pq+aI1/2 (a, empirical parameter). Comparison with literature findings is given and some recommended values are reported.