The precipitation of some actinide element complex ions by using hexammine cobalt(III) cation—VI The precipitation of Np(IV), (V) and (VI) sulfate complex ions with hexammine cobalt(III) cation

Abstract

Precipitation behaviors of Np(IV), (V) and (VI) in sulfuric acid and ammonium sulfate solutions with hexammine cobalt(III) ion have been studied. The optimum conditions of precipitating Np as crystalline compounds are 0.4 M H 2SO 4 and 0.06 M [Co(NH 3) 6]Cl 3 for Np(IV), larger than 0.5 M (NH 4) 2SO 4 and 0.03 M [Co(NH 3) 6]Cl 3 for Np(V), and the higher the concentrations the better for Np(VI). Np(IV) is completely removed from ammonium sulfate solution. Composition of the Np(IV) compound from the sulfuric acid solution is [Co(NH 3) 6] 2[Np(SO 4) 5]· nH 2O. And composition of the Np(V) compounds is possibly [Co(NH 3) 6][NpO 2(SO 4) 2]·α[Co(NH 3) 6] 2(SO 4) 3· nH 2O (α = 2.20−0.32). Solubilities of the Np(IV), (V) and (VI) compounds in water are found to be 4.9 mgNp/l, 520 mgNp/l, and 250 mgNp/l, respectively.