Thermoelectric Properties of M sup 4+ /M sup 3+ and MO sub 22+ /MO sub 2+ Redox Couples of Neptunium and Plutonium in Aqueous HClO sub 4 and HNO sub 3 Media

摘要

The thermoelectric properties of redox couple of transuranium elements in acidic, slightly complexing media have been considered. The electromotive force between two inert electrodes in contact with an aqueous solution containing the reversible redox couple and subjected to two different temperature is the product of the temperature gradiant by the thermoelectric power of the redox couple and experimental data are in good agreement with the theoretical calculated value of 0.198 mV/K. The variations of thermoelectric power E versus the ionic strength are very close to theoretical values MO sub 22+ /MO sub 2+ couples but for M exp 4+ /M exp 3+ couples a decrease of HClO sub 4 or HNO sub 3 acid concentrations induces a diminution of E for Pu exp 4+ /Pu exp 3+ and a maximum for Np exp 4+ /Np exp 3+ ; the origin of the discrepancy is certainly the hydrolysis of the acidic cations: Np exp 4+ and Pu exp 4+ . No significant differences were found beetween the HClO sub 4 and HNO sub 3 media. (ERA citation 09:028966)