The kinetics of the reaction between Np(VI) and butyraldehyde isomers in nitric acid solution was studied to find flow-sheet conditions of the Np separation process from U and Pu. Iso-butyraldehyde was found to have a higher reduction rate than n-butyraldehyde. The former reduction rate at T = 283 to 323 K is described by the following equation:

-d[Np(VI)]/dt
= 6.0 × 106exp(-4.1 × 103/T)
× [Np(VI)][iso-C3H7CHO]0[H+] (M/min).

The latter reduction rate is described by the following equation:

-d[Np(VI)]/dt
= 4.2 × 104exp(-3.4 × 103/T)
× [Np(VI)][n-C3H7CHO]0[H+] (M/min).