KINETICS OF NP(IV) OXIDATION WITH PERSULFATE IN ALKALI SOLUTIONS

A 7 x 10(-3) M suspension of neptunium(IV) hydroxide in deaerated 0.5- 14 M NaOH is oxidized with S2O82- to give successively Np(V), Np(VI), and Np(VII). The rates of all the reactions increase with temperature and with increasing concentrations of alkali and the oxidant. In 4-14 M NaOH, Np(IV) within less than 10 min at 21 degrees C is oxidized wit h 0.02 M S2O82- into Np(VI), which passes into the solution; this is f ollowed by formation of Np(VII). A mechanism is proposed involving rea ctions of S2O82- with solid Np(OH)(4) and with dissolved Np(V) and Np( VI) hydroxides.