Kinetics of Redox Reactions of U, Np, and Pu in TBP Solutions: IX. Reduction of Np(VI) with Dibenzylhydrazine

Abstract

The kinetics of reduction of Np(VI) with dibenzylhydrazine in TBP nitric acid solutions was studied. At the reductant excess Np(V), nitrogen, and benzyl alcohol were the reaction products. At low HNO3 concentration (<0.03 M), the reaction went to completion, while at a higher acid content in TBP the equilibrium was attained, shifting to Np(VI) with increasing acidity. Taking into account direct and reverse reactions, the rate of Np(VI) to Np(V) transformation was described by the equation -d[Np(VI)]/dt = k[Np(VI)]× [(C6H5CH2)2N2H2][H2O]0.4 - k 3[Np(V)]2[HNO3]1.2, where k = 64±6 l1.4 mol- 1.4 min-1 and k 3 = 4480± 450 l2.2 mol- 2.2 min-1 at 40°C. The activation energy of the direct reaction was E = 42.7±2.2 kJ mol- 1. The dilution of TBP with n-dodecane did not affect the reaction rate. The reaction mechanism was discussed.