Kinetics of neptunium(V) reduction with iron(II) sulfamate in nitric acid solutions.

The kinetics of chemical reduction of Np(V) with iron(II) sulfamate in HNO solutions was studied by spectrophotometry. The reduction process can be described by the equation NpO + Fe + 4H ⇆ Np + Fe + 2HO and follows the first- and zero-order rate law with respect to the Np(V) concentration. The reaction rate constants were determined in relation to the HNO concentration (1-3 M), iron(II) sulfamate concentration [(0.59-2.94) × 10 M], and temperature (298.2-319.2 K). The activation energy ( E) and the thermodynamic functions of formation of the activated complex (activation free energy Δ G, enthalpy Δ H, entropy Δ S) were calculated. [ABSTRACT FROM AUTHOR]