Investigation of neptunium (V) reduction to neptunium (IV) by semiconductor photocatalysis

This paper reports that when a 1 mM Np(V) solution of 3 M nitric acid was irradiated by a xenon lamp with n-SiC (5 mg dm-3) as photocatalyst and hydrazine (0.1 M) as donor, 100% of the Np(V) was reduced to Np(IV) within 30 min at room temperature. Electrochemical investigations suggested that Np(V) is reduced by the atomic hydrogen adsorbed on the photocatalyst surface. According to this mechanism, platinum group metals can act as reducing catalysts for Np(V) reduction because of their low hydrogen overvoltage. The proposed mechanism was experimentally confirmed by using platinum black (5 mg dm-3) as catalyst and hydroxylammonium nitrate (0.9 M) as reducing agent