Publication Abstract

Influence of some seawater components on the sorption behaviour of Neptunium(V)

D. McCubbin and K.S. Leonard

The fate of neptunium in the aquatic environment is dependent upon, amongst other processes, the extent of uptake by particulate material. In oxic natural waters it exists predominantly in the V valent state. A number of laboratory experiments have been carried out, using 239Np tracer, particulate material prepared from Irish Sea sediment and various synthetic solutions, to determine the influence of chemical parameters on the sorption behaviour of Np(V) in marine waters. The data suggest that uptake is highly dependent upon solution pH both as a result of changes in charge on particle surfaces and, at high pH values (>9.0), from the formation of hydrolysis species. Np(V) uptake by marine particulate material was essentially independent of ionic strength within the pH range of natural seawater. The presence of Mg²⁺, Ca²⁺ and HC0₃^- ions was found to inhibit Np(V) sorption; removal of Np(V) was, however, increased from solutions which were supersaturated with respect to CaC0₃. The data indicate that, although Np(V) sorption in seawater is controlled by interactions between Mg²⁺, Ca²⁺ and HC0₃^-, the effect of the combined presence of all three constituents is more complex than might be expected from the action of individual components.

Reference:

D. McCubbin and K.S. Leonard, 1995. Influence of some seawater components on the sorption behaviour of Neptunium(V). Radiochemical Acta 69: 97-102.