A preliminary study of the reduction of Np(VI) by formohydroxamic acid using stopped-flow near-infrared spectrophotometry

Abstract

The kinetics of the reduction of NpO 2 2+ to NpO 2 + in nitric acid aqueous solution by formohydroxamic acid (FHA) were studied to allow more accurate flow sheet modelling of neptunium separation from uranium and plutonium in an Advanced PUREX process. The rate of the reaction was monitored using stopped-flow spectrophotometry with near-infrared detection. The conditional reduction rate in 2 M nitric acid at 22°C could be described by the following equation: -d [NpO 2 2+ ]/dt = k [NpO 2 2+ ][FHA](M/s) with k = 1.17×10 3 M -1 s -1 at [H + ] = 2.0 M. Comparison with other data available in the literature, indicates that formohydroxamic acid is an unusually strong reducing agent for NpO 2 2+ .